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Full text of "Locomotor morphology of the vampire bat, Desmodus rotundus"

QL 
737 
..•C52 
M6 



_^ OMOTOR MORPHOLOGY 
OF THE VAMPIRE BAT, 
DESMODUS ROTUNDUS 



ALTENBACH 



mi . 
A 46 



HARVARD UNIVERSITY 

Library of the 

Museum of 

Comparative Zoology 



LOCOMOTOR MORPHOLOGY 
OF THE VAMPIRE BAT, 
DESMODUS ROTUNDUS 



SPECIAL PUBLICATIONS 

This series, published by the American Society of Mammalo- 
gists, has been established for papers of monographic scope con- 
cerned with some aspect of the biology of mammals. 

Correspondence concerning manuscripts to be submitted for 
publication in the series should be addressed to the Editor for 
Special Publications, Hugh H Genoways, Carnegie Museum 
of Natural History, 4400 Forbes Avenue, Pittsburgh, Pennsyl- 
vania 15213. 

Copies of special publications may be ordered from the Secre- 
tary-Treasurer of the Society, Duane A. Schlitter, Carnegie 
Museum of Natural History, 4400 Forbes Avenue, Pittsburgh, 
Pennsylvania 15213. 

Price of this issue $10.00 



COMMITTEE ON SPECIAL PUBLICATIONS 

James N. Layne, Editor 

Archbold Biological Station, 

Route 2, Box 180, 

Lake Placid, Florida 33852. 

J. Knox Jones, Jr., Managing Editor 
The Museum, 
Texas Tech University 
Lubbock, Texas 79409 



CONSULTING EDITORS FOR THIS ISSUE 

Clyde Jones 
Don E. Wilson 



This publication was hnanced in part by a gift from David Klingener. 



LOCOMOTOR MORPHOLOGY 
OF THE VAMPIRE BAT, 
DESMODUS ROTUNDUS 



By 

J. SCOTT ALTENBACH 

Department of Biology 

University of New Mexico 

Albuquerque, New Mexico 87131 



SPECIAL PUBLICATION NO. 6 
THE AMERICAN SOCIETY OF MAMMALOGISTS 

Published 22 August 1979 



131 



tii 



A^4 



MUS. COMP. ZOOL 
LIBRARY 

OCT 11980 

HARVARD 
UNIVERSITY 

4^ 



Library of Congress Catalog Card No. 79-53175 
D 1979 by The American Society of Mammalogists 



FOREWORD 

ONE obvious objective of any functional morphological study is 
to determine how anatomical features operate. Far more im- 
portant, however, is the interpretation of the adaptive significance 
of those anatomical features and the role their functioning plays 
in the evolutionary, as well as the day-to-day, biology of an organ- 
ism. Although morphological features have been used widely for 
taxonomic purposes for centuries, only relatively recently has in- 
terpretation of the functional significance of morphological fea- 
tures been applied toward understanding the biology of organ- 
isms. That this is especially true of locomotor morphology is 
somewhat surprising, because locomotion plays such a critical role 
in the survival of the vast majority of heterotrophic organisms. 

Few, if any, groups of animals have as broad a spectrum of 
locomotor styles as do mammals. Certainly much of their abun- 
dance and general success has been a function of evolution of such 
diversity in locomotor mechanisms. The locomotion of bats is es- 
pecially interesting, because both pelvic and pectoral limbs are used 
in aerial as well as terrestrial locomotion. Evolutionary compromise 
has variously placed different bats on a spectrum between extreme 
limb modification for certain types of flight and modification for 
more efficient terrestrial locomotion. 

The study of a biological extreme, whether it is a community, 
an organism, or a functional system within an organism, can often 
clarify the mechanisms of operation of the average or less extreme. 
This is particularly true in the study of bat locomotion where the 
outstanding locomotor specialization, flight, is rather poorly 
understood. The common vampire bat {Desmodus rotundus) is an 
ideal candidate for locomotor morphology studies because it rep- 
resents an extreme in locomotor specialization. It seems logical that 
a flying machine can vary or be modified evolutionarily in relatively 
few ways and still fly. The vampire bat has seemingly approached 
the limit of evolutionary modification by specializing in rapid and 
effective terrestrial locomotion while retaining the ability to fly. 
A functional morphological investigation of the vampire bat as a 
flying machine should not only clarify the flight mechanics of oth- 
er, less extreme, bats, but also facilitate interpretation of the role 
of flight-associated morphology. Of equal interest is the study of 
the terrestrial locomotor modifications that make the vampire so 
extreme. 



My study of the locomotor morphology of the vampire was un- 
dertaken both to interpret the functional significance of its loco- 
motor-associated anatomy to provide another viewpoint in our bi- 
ological knowledge of this animal and to stimulate others to add 
additional interpretation of functional morphology to bat biology, 
as well as to the biology of other organisms. Only description of 
the anatomical details of the pectoral girdle and limb is included 
in this work. Admittedly the pelvic girdle and limb are important 
in locomotion in the vampire bat and show specializations for its 
unique locomotor mechanisms. However, I feel that the most spec- 
tacular of the anatomical specializations for terrestrial locomotion 
and certainly the most important specializations for flight are those 
of the pectoral limb and girdle, and I have thus focused my atten- 
tion on these structures. Perhaps this work will stimulate publica- 
tions of functional morphological data on the pelvic girdle and 
limb. 

I want to thank Terry Vaughan for his encouragement at the 
onset of this study. Paul Baldwin, Rowan Frandson, Thomas Bahr, 
and Y. Z. Abdelbaki gave encouragement, generously loaned 
equipment, and read the manuscript as prepared as a doctoral 
dissertation. Marilyn Altenbach contributed countless hours in 
help with surgical procedures, typing, and proofreading the 
manuscript. Without her assistance and encouragement this work 
would not have been possible. Sincere thanks are due to the per- 
sonnel of the U.S. Fish and Wildlife Service at the Denver Wildlife 
Research Center for the generous loan of living vampire bats and 
to Northern Arizona University for the loan of preserved speci- 
mens. I deeply appreciate the help of Janice Moore and Lyle Ber- 
ger, who read proof of the final manuscript, and want to thank 
James Findley, Patricia Freeman, and Michael Bogan, who criti- 
cally read portions of the manuscript. I also thank James N. Layne 
for his encouragement and his very time-consuming editorial 
work, and Lorene Deckert who typed the final manuscript. 

I would like to dedicate this monograph to my major professor, 
the late Robert R. Lechleitner. He was the finest teacher I have 
ever known and I can only hope to be a scientist of his competence 
and a human being of his kindness. To his family I express sincere 
thanks for the kindness and generosity shown to me and their 
encouragement of my research. 



CONTENTS 



Introduction 1 

Materials and Methods 5 

Preservation and Dissection 5 

Photographic Procedures 5 

Electromyography 7 

Locomotion 10 

Standing Postures 10 

Hanging Posture 12 

Walking 12 

Hopping Locomotion 14 

Climbing 17 

Jumping Behavior 18 

Initial Flight Following a Jump 31 

Slow Forward Flight 41 

Alighting Maneuvers on Horizontal Surfaces 49 

Alighting Maneuvers on Vertical Surfaces 51 

Postcranial Osteology 52 

Positional Terminology 52 

Vertebral Column 53 

Sternum 55 

Ribs 56 

Pectoral Girdle and Limb 56 

Scapula 56 

Clavicle 59 

Humerus 60 

Radius and Ulna 64 

Manus 66 

Digit I 68 

Digit II 69 

Digit III 69 

Digits IV and V 70 

Functional Myology of the Pectoral Girdle and Limb 72 

Comments on Electromyographic Analysis 72 

Muscles Unique to Bats 73 

M. occipito-pollicalis 73 

M. propatagialis proprius 74 

M. coraco-cutaneus 75 



Muscles of the Pectoral Girdle and Limb 75 

Trapezius Group 75 

M. clavotrapezius 75 

M. acromiotrapezius 78 

M. spirotrapezius 78 

Costo-spino-scapular Group 79 

M. levator scapulae 79 

M. serratus anterior, anterior division 79 

M. serratus anterior, posterior division 80 

M. rhomoboideus 8 1 

M. omocervicalis 83 

Latissimus-subscapular Group 83 

M. latissimus dorsi 83 

M. teres major 84 

M. subscapularis 84 

Deltoid Group 84 

M. clavodeltoideus 84 

M. acromiodeltoideus 85 

M. spinodeltoideus 87 

M. teres minor 89 

Suprascapular Group 89 

M. supraspinatus 89 

M. infraspinatus 90 

Triceps Group 90 

M. triceps brachii, caput lateralis 90 

M. triceps brachii, caput medialis 90 

M. triceps brachii, caput longus 90 

Extensor Group of the Forearm 93 

M. extensor carpi radialis brevis 93 

M. extensor carpi radialis longus 93 

M. supinator 95 

M. extensor poinds brevis 95 

M. abductor pollicis longus 96 

M. extensor digiti quinti proprius 97 

M. extensor digitorum communis 97 

M. extensor carpi ulnaris 98 

M. extensor indicis 99 

Pectoralis Group 99 

M. subclavius 99 

M. pectoralis 100 

M. pectoralis, anterior (clavicular) division 100 

M. pectoralis, posterior (sternal) division 101 

M. pectoralis abdominalis 102 

Flexor Group of the Arm 102 

M. coracobrachialis 102 

M. biceps brachii 103 

M. brachialis 104 



Flexor Group of the Forearm 104 

M. flexor carpi ulnaris 104 

M. palmaris longus 105 

M. flexor carpi radialis 107 

M. pronator teres 108 

M. flexor digitorum profundus 108 

Extensors of the Manus 109 

M. interosseus dorsale 109 

Flexor Group of the Manus 110 

M. abductor pollicis brevis 110 

M. flexor pollicis brevis 110 

M. adductor pollicis 111 

Mm. interossei 112 

M. abductor digiti quinti 1 14 

M. opponens digiti quinti 115 

Discussion 116 

Terrestrial Locomotor Behavior 116 

Flight and Aerodynamic Considerations 119 

Anatomical Considerations 124 

Summary 129 

Literature Cited 132 

Index 135 



My study of the locomotor morphology of the vampire was un- 
dertaken both to interpret the functional significance of its loco- 
motor-associated anatomy to provide another viewpoint in our bi- 
ological knowledge of this animal and to stimulate others to add 
additional interpretation of functional morphology to bat biology, 
as well as to the biology of other organisms. Only description of 
the anatomical details of the pectoral girdle and limb is included 
in this work. Admittedly the pelvic girdle and limb are important 
in locomotion in the vampire bat and show specializations for its 
unique locomotor mechanisms. However, I feel that the most spec- 
tacular of the anatomical specializations for terrestrial locomotion 
and certainly the most important specializations for flight are those 
of the pectoral limb and girdle, and I have thus focused my atten- 
tion on these structures. Perhaps this work will stimulate publica- 
tions of functional morphological data on the pelvic girdle and 
limb. 

I want to thank Terry Vaughan for his encouragement at the 
onset of this study. Paul Baldwin, Rowan Frandson, Thomas Bahr, 
and Y. Z. Abdelbaki gave encouragement, generously loaned 
equipment, and read the manuscript as prepared as a doctoral 
dissertation. Marilyn Altenbach contributed countless hours in 
help with surgical procedures, typing, and proofreading the 
manuscript. Without her assistance and encouragement this work 
would not have been possible. Sincere thanks are due to the per- 
sonnel of the U.S. Fish and Wildlife Service at the Denver Wildlife 
Research Center for the generous loan of living vampire bats and 
to Northern Arizona University for the loan of preserved speci- 
mens. I deeply appreciate the help of Janice Moore and Lyle Ber- 
ger, who read proof of the final manuscript, and want to thank 
James Findley, Patricia Freeman, and Michael Bogan, who criti- 
cally read portions of the manuscript. I also thank James N. Layne 
for his encouragement and his very time-consuming editorial 
work, and Lorene Deckert who typed the final manuscript. 

I would like to dedicate this monograph to my major professor, 
the late Robert R. Lechleitner. He was the finest teacher I have 
ever known and I can only hope to be a scientist of his competence 
and a human being of his kindness. To his family I express sincere 
thanks for the kindness and generosity shown to me and their 
encouragement of my research. 



CONTENTS 



Introduction 1 

Materials and Methods 5 

Preservation and Dissection 5 

Photographic Procedures 5 

Electromyography 7 

Locomotion 10 

Standing Postures 10 

Hanging Posture 12 

Walking 12 

Hopping Locomotion 14 

Climbing 17 

Jumping Behavior 18 

Initial Flight Following a Jump 31 

Slow Forward Flight 41 

Alighting Maneuvers on Horizontal Surfaces 49 

Alighting Maneuvers on Vertical Surfaces 51 

Postcranial Osteology 52 

Positional Terminology 52 

Vertebral Column 53 

Sternum 55 

Ribs 56 

Pectoral Girdle and Limb 56 

Scapula 56 

Clavicle 59 

Humerus 60 

Radius and Ulna 64 

Manus 66 

Digit I 68 

Digit II 69 

Digit III 69 

Digits IV and V 70 

Functional Myology of the Pectoral Girdle and Limb 72 

Comments on Electromyographic Analysis 72 

Muscles Unique to Bats 73 

M. occipito-pollicalis 73 

M. propatagialis proprius 74 

M. coraco-cutaneus 75 



Muscles of the Pectoral Girdle and Limb 75 

Trapezius Group 75 

M. clavotrapezius 75 

M. acromiotrapezius 78 

M. spirotrapezius 78 

Costo-spino-scapular Group 79 

M. levator scapulae 79 

M. serratus anterior, anterior division 79 

M. serratus anterior, posterior division 80 

M. rhomoboideus 8 1 

M. omocervicalis 83 

Latissimus-subscapular Group 83 

M. latissimus dorsi 83 

M. teres major 84 

M. subscapularis 84 

Deltoid Group 84 

M. clavodeltoideus 84 

M. acromiodeltoideus 85 

M. spinodeltoideus 87 

M. teres minor 89 

Suprascapular Group 89 

M. supraspinatus 89 

M. infraspinatus 90 

Triceps Group 90 

M. triceps brachii, caput lateralis 90 

M. triceps brachii, caput medialis 90 

M. triceps brachii, caput longus 90 

Extensor Group of the Forearm 93 

M. extensor carpi radialis brevis 93 

M. extensor carpi radialis longus 93 

M. supinator 95 

M. extensor pollicis brevis 95 

M. abductor pollicis longus 96 

M. extensor digiti quinti proprius 97 

M. extensor digitorum communis 97 

M. extensor carpi ulnaris 98 

M. extensor indicis 99 

Pectoralis Group 99 

M. subclavius 99 

M. pectoralis 100 

M. pectoralis, anterior (clavicular) division 100 

M. pectoralis, posterior (sternal) division 101 

M. pectoralis abdominalis 102 

Flexor Group of the Arm 102 

M. coracobrachialis 102 

M. biceps brachii 103 

M. brachialis 104 



Flexor Group of the Forearm 104 

M. flexor carpi ulnaris 104 

M. palmaris longus 105 

M. flexor carpi radialis 107 

M. pronator teres 108 

M. flexor digitorum profundus 108 

Extensors of the Manus 109 

M. interosseus dorsale 109 

Flexor Group of the Manus 110 

M. abductor pollicis brevis 110 

M. flexor pollicis brevis 110 

M. adductor pollicis 111 

Mm. interossei 112 

M. abductor digiti quinti 114 

M. opponens digiti quinti 115 

Discussion 1 16 

Terrestrial Locomotor Behavior 116 

Flight and Aerodynamic Considerations 119 

Anatomical Considerations 124 

Summary 129 

Literature Cited 132 

Index 135 



INTRODUCTION 

ALTHOUGH bats have been studied intensively for many years, 
relatively little has been learned about the mechanisms of 
locomotion and the anatomical features involved with locomotion 
in this large order of mammals. The preliminary work in the field 
of chiropteran locomotor morphology is restricted to relatively few 
species of bats and emphasizes the need for investigation of ana- 
tomical specialization and, particularly, the modes of locomotion 
in other species. 

Cuvier (1800, et seq.), Kolenati (1857), and Humphry (1869) 
published papers on bat anatomy, but Macalister (1872) was the 
first to standardize anatomical terminology for this order and to 
correct errors of earlier investigators. Macalister described the 
myology of 19 species representing the families Pteropidae, Rhi- 
nolophidae, Megadermidae, Phyllostomatidae, and Vespertilioni- 
dae, and his work remained the major reference in chiropteran 
myology until 1959. Maisonneuve (1898) described the osteology 
and myology of Vespertilio murinus and Levy (1912) described the 
myology of the upper arm and shoulder of 16 species of bats. 
Petersen (1923) studied the osteology of the arm and carpus of 
Vespertilio murinus. Eisentraut (1936) published photographs of 
Myotis myotis, Rhinolophus hipposideros, and Plecotus auritus in flight, 
and presented the first analysis of the mechanics of flight in bats. 
He carefully described the phases of the wingbeat and determined 
where thrust and lift were generated. Although the photographic 
material available to him was of poor quality, he was able to rec- 
ognize that interspecific differences exist in flight mechanisms and 
that different types of flight observed in a single species require 
different movements. 

Vaughan (1959) correlated differences in limb and girdle mor- 
phology with differing modes of flight, terrestrial locomotion, and 
roosting habits. This publication standardized chiropteran myo- 
logical terminology and has remained the major reference on chi- 
ropteran locomotor morphology. Later publications by Vaughan 
(1966, 1970a, 1970^, 1970c, 1970^, 1970^) further illustrate ana- 
tomical specialization to fit a particular mode of locomotion or 
behavior. Struhsaker (1961) attempted to correlate interspecific 
differences in flight patterns with differences in relative weights 



2 Spec. Publ. Amer. Soc. Mamm. 6 

of specific flight muscles and the dimensional relationships of the 
flight membranes. However, incorrect analysis of the mode of 
flight of one species makes certain of his conclusions questionable. 
His paper does provide dimensional relationships that are valuable 
for comparison. Hartman (1963) calculated dimensional and di- 
mension/weight ratios for 12 species of bats, including the vampire 
bat, of five families. His data are useful for comparison and show 
interesting aerodynamic relationships. Gaisler (1964) published 
observations on the flight of several European species and con- 
firmed some of the conclusions of Eisentraut. Findley et al. (1972) 
presented data on morphologic properties of bat wings and spec- 
ulated on their functional significance. 

Altenbach (1968) described the appendicular anatomy and flight 
of a hovering species (Leptonycteris sanborni) and compared them to 
those of a species {Eptesicus fuscus) that flies rapidly and cannot 
hover. The contrasts clarified the significance of many anatomical 
features of both species. Walton (1968) described the appendicular 
osteology in members of the family Phyllostomatidae. This paper 
did not consider functional significance but is a valuable anatomical 
reference for this family. Vaughan and Bateman (1970) correlated 
differences in foraging behavior with variations in forelimb mor- 
phology in the families Mormoopidae and Phyllostomatidae. 

Norberg (1970a, 1970^) published a beautifully illustrated de- 
scription of the osteology and myology of the pectoral limb of 
Plecotus auritus, and an account of hovering flight in this species. 
Norberg (1969) also discussed the bracing system that is seen in 
the leading edge of the "hand-wing" of bats. 

The difficulties encountered photographing small flying animals 
in anything but highly restrictive enclosures are severe. Virtually 
no detailed research on bat locomotion has been attempted except 
by Eisentraut (1936), and the data he had to work with did not 
allow thorough analysis of the mechanisms involved. 

Much of the literature concerning bat locomotion, particularly 
flight, is based on indirect evidence. Dimensional relationships of 
flight membranes, dimension/weight relationships, positional re- 
lationships of myological and osteological components of the gir- 
dles and appendages, and visual observations of bats in flight and 
terrestrial locomotion can lead to reasonably accurate conclusions 
about the mechanics of locomotion. However, only high-speed 
photography can clearly illustrate the mechanisms involved and 



Altenbach — Vampire Locomotor Morphology 3 

the often subtle interspecific differences. When high-speed pho- 
tographic data are available, anatomical features can be correlated 
with movements that are peculiar to specific types of locomotion. 

The objectives of this study were: (1) to analyze through the use 
of high-speed still and motion picture photography the mecha- 
nisms of walking, hopping, jumping, climbing, and flight used by 
Desmodus rotundus; (2) to describe the pectoral girdle and the ap- 
pendicular osteology and myology by dissection of preserved spec- 
imens and examination of skeletons; (3) to determine how some 
of the muscles involved with locomotion function during normal 
movements by simultaneous photography and electromyography; 
(4) to determine the functional significance of pectoral girdle and 
appendicular anatomy in the locomotion of Desmodus; and (5) to 
determine, if possible, the significance of specialized locomotor 
behavior in Desmodus. 

It is surprising that the locomotion of the common vampire bat 
has not heretofore been investigated in detail and that not more 
than a cursory examination of its appendicular anatomy has been 
attempted. In contrast, the distribution, feeding behavior, and par- 
ticularly the role of this species as a vector of disease of man and 
domestic animals have been the subject of many published ac- 
counts. 

The agility and delicate walking behavior of this species were 
described by Beebe (1927) and Price (1950) from observations 
made on vampires attempting to feed on them. Ditmars and 
Greenhall (1935, 1960) related the account of an explorer who 
noted that Desmodus "walked" or "hopped from one spot to 
another." These authors described the ability of vampires to walk, 
climb, and jump into flight from the ground and published the 
first photographs of the terrestrial locomotion of this species (Dit- 
mars, 1934; Ditmars and Greenhall, 1935, 1960). The photographs 
illustrate the characteristic walking gait of the bat, the posture 
when drinking from a dish, and the feeding posture on the back 
of a live goat. The authors commented that Desmodus moved rap- 
idly over the back of the goat to avoid being brushed off as the 
animal walked under obstacles. 

Dalquest (1955) noted the extreme terrestrial agility oi Desmodus, 
its ability to hop and to jump into flight from the ground, and its 
characteristic swift and direct flight. Wimsatt (1959) noted that 
Desmodus could rapidly "scramble" across vertical surfaces and used 



4 Spec. Publ. Amer. Soc. Mamm. 6 

hopping and leaping jumps in terrestrial locomotion. He also re- 
marked on its strong, swift flight and its habit of flying within a 
meter of the ground. Mohr (1955) also mentioned the agility of 
this bat and the "crab" or "spider-like" way it moves over vertical 
surfaces. He also observed vampires taking flight from the ground 
after being knocked from a roost by the blast of a gun. Leen and 
Novick (1970) referred to the jumping behavior of Desmodus and 
published photographs of individuals standing and jumping. 

Many authors have suggested that the terrestrial locomotor abil- 
ity of the vampire is useful in feeding behavior but provide only 
scant evidence to support this hypothesis. An account by Hensel 
(1869) stated that in South America cattle are bitten by Desmodus 
about the hooves, and recent evidence from Mexico (Mitchell, 1970; 
Robert Tigner, personal communication) indicates that individuals 
often feed from the ground by biting cattle on the fetlock and, if 
necessary, follow the animal while taking blood from the wound. 
The agility and the ability to jump appear necessary to avoid being 
crushed while feeding and to take flight from the ground. Motion 
pictures taken by A. M. Greenhall show Desmodus feeding on un- 
restrained guinea pigs and illustrate the use of the terrestrial agility 
and walking behavior to catch and feed on these active rodents. 

Although a few other species of bats move readily on the ground 
(Burt, 1934; Vaughan, 1959, 1970^; Leen and Novick, 1970) and 
some can take off from the ground (Eisentraut, 1936; Vaughan, 
1959; Anonymous, 1969), no other species possesses the extreme 
terrestrial agility and jumping ability of Desmodus. 



MATERIALS AND METHODS 



Preservation and Dissection 

TEN Desmodus rotundus from near San Bias, Nayarit, and eight 
from near Mazatlan, Sinaloa, were preserved in 10 per cent 
formalin and stored in 70 per cent ethyl alcohol. Additional frozen 
specimens were obtained from the Denver Wildlife Research Cen- 
ter of the U.S. Fish and Wildlife Service and were preserved and 
stored in the same manner. 

Several preserved bats were dissected under a binocular micro- 
scope with variable magnification from seven to 30 power. These 
bats were stored in a solution of one part glycerin and eight parts 
70 per cent ethyl alcohol, which prevented desiccation and soft- 
ened muscles. Photographs of the dissections were taken with a 35 
mm camera for aid in preparation of anatomical drawings. 

Skeletons of a male and a female bat from the collection of 
Northern Arizona University were used for a description of osteo- 
logical features. A bat from Nayarit, Mexico, was cleared in two 
per cent KOH solution, stained with Alizarin Red S, and stored in 
glycerin for use in description of osteological features of the car- 
pus. X-ray photographs of another of the Nayarit specimens were 
taken by Y. Z. Abdelbaki of the Anatomy Department, Colo- 
rado State University, for preparation of anatomical drawings. 

Photographic Procedures 

Patterns of terrestrial and aerial locomotion were analyzed by 
means of high-speed still and motion pictures. Bats used in this 
phase of the study were maintained in the laboratory on a diet of 
defibrinated beef blood and housed in separate containers made 
from 2-liter freezer cartons. 

All still photographs were taken with a Praktiflex 35 mm single 
lens reflex camera on Kodak Panatomic X film with illumination 
provided by a 100 watt second electronic flash unit of my own 
design. The V15000 second flash eliminated blur and permitted 
an aperture of f/16 with the three lamp heads positioned 50 cm 
from the bat. A black velveteen backdrop was positioned be- 
hind the flight path of the bat and the camera shutter was 



6 Spec. Puhl. Amer. Soc. Mamm. 6 



wire cage 



\ 



black backdrop 




Hycam K2004E 



50 mm lens 
— light trap 

Tektronix 502 A 
oscilloscope 



Fig. 1 . Diagram of the equipment used in the electromyographic experiments. 
Two additional lights not illustrated were positioned above the wire cage. The plug 
and cable, preamplifier, and oscilloscope were not used in general high-speed pho- 
tography of locomotion, but the position of the lights, wire cage, and camera was 
similar. 



Altenbach — Vampire Locomotor Morphology 7 

opened prior to the exposure. After the flash was triggered, the 
shutter was closed. Since light in the room was normally low, no 
fogging of the film occurred; the only exposure was produced by 
the V15000 second flash. Photographs of the bats in motion were 
taken as they interrupted a light beam directed on a photocell that 
in turn activated an advance relay triggering the flash. Bats were 
directed into a prescribed area by baffles or released from beneath 
an inverted bowl. Photographs of bats standing and climbing were 
taken manually by use of a toggle switch that triggered the flash. 
High-speed motion pictures were taken with a Hycam K2004E 
camera. Kodak Four-X reversal 16 mm film was used in 100-foot 
rolls and forced to ASA 800 during development. Four lights to- 
taling 3400 watts output provided sufficient illumination to use an 
aperture of f/8 at 250 fps (frames per second), 5.6 at 500 fps, and 
4 or 2 at 1000 fps. The bats were positioned under an inverted 
cup in an open-fronted wire flight compartment 0.6 m wide, 
0.9 m high, and 0.9 m deep that was lined on the bottom 
and back with black velveteen. The camera was focused on the 
center of this compartment and the lights were positioned in front 
of it (Fig. 1). In photographing bats with this set-up, the lights 
were switched on, the camera started, then the cover pulled off 
the bat. Motion pictures of flight from the side were taken as the 
bat flew from baffles into a room. 

Electromyography 

To determine the temporal sequence of contraction of certain 
muscles during normal movements, stainless steel electrodes 0.001 
inch in diameter were implanted in the muscles and exteriorized 
through an implanted silicone rubber plug (Altenbach, 1972). A 
two-conductor shielded cable 1 m long with a soft plastic in- 
sulator was adapted with a three-pin male plug for attachment to 
the female plug sutured to the bat. The contacts could be adjusted 
to allow separation of the plugs with a gentle tug, preventing injury 
to the bat when it moved beyond the length of the connecting 
cable. The cable connected to a Grass model PI 5- A AC preampli- 
fier that provided a gain of 10, 100, or 1000 to the myopotential 
changes monitored in the bat. The connecting cable and pream- 
plifier were arranged in a grounded cage of 6-mm hardware cloth 



8 Spec. Publ. Amer. Soc. Mamm. 6 

with the cable running through a wire partition (Fig. 1). A heavy 
shielded cable connected the preamplifier to a Tektronix 502-A 
dual beam oscilloscope. 

The high-speed motion picture camera and lights were posi- 
tioned in front of the cage as described in the section on pho- 
tography. The objective lens was focused on the flight com- 
partment of the cage and a 50-mm lens mounted on the rear 
focusing aperture was focused on the screen of the oscilloscope 
60 cm behind the camera. This technique superimposed an 
electromyographic trace over the frame by frame record of the 
action in the cage. In this type of oscillography the cathode beam 
is not swept by a horizontal amplifier but is positioned in the center 
of the tube. The deflections are vertical and correspond, in this 
case, to potential changes in a muscle. 

The camera was operated at 200, 250, and 500 fps for the elec- 
tromyographic experiments, and the same film and processing de- 
scribed for motion picture photography were used. The oscillo- 
graphic trace was transferred to paper tape for analysis by a device 
that moved the film and paper tape parallel to each other at dif- 
ferent speeds. A stylus was moved to follow the vertical deflections 
in the myographic trace on the film, and a pen attached to the 
stylus transcribed the trace onto the paper tape. This method al- 
lowed the trace reproduced on the paper tape to be condensed 
horizontally to readable and reproducible proportions. For ex- 
ample, if the film was moved past the stylus at twice the speed of 
the tape, the trace on the film was condensed 50 per cent on the 
tape. Register marks were put on every fifth frame of the motion 
picture film and at corresponding points on the tape to correlate 
the myographic streak with the movements of the bat. 

Because myopotential changes seldom exceeded 2 millivolts, a 
gain of 100 was sufficient for preamplification and the oscilloscope 
vertical amplifier was set at 50 millivolts/cm. Thus a potential 
change of 2 millivolts produced a 4-cm deflection of the elec- 
tron beam. 

Tracings were made from the films for illustration of the move- 
ments for correlation with the electromyographic traces. No timing 
marks were put on the film because the camera was speed regu- 
lated to ± 1 per cent and periodically checked for accuracy. Dif- 
ferences of 1 per cent are negligible and calculations of elapsed 
time can be made by frame counts. Slight differences in speed of 



Altenbach — Vampire Locomotor Morphology 9 




Fig. 2. Alert standing postures oi Desmodus rotundus: A, inclined slighdy; B, 
horizontal; C, steeply inclined. 



10 spec. Publ. Amer. Soc. Mamm. 6 

the film do not affect the correlation of movement with myopo- 
tential changes inasmuch as the two are recorded simultaneously. 



LOCOMOTION 



Standing Postures 

IN alert standing postures, Desmodus often holds the body 2 or 3 
cm above the substrate and inclined upward between 10 and 
50 degrees above the horizontal (Fig. 2A). The thighs are oriented 
laterally and the knees are flexed 60 to 90 degrees and usually 
oriented perpendicular to the substrate, with the feet directed pos- 
terolaterally. The weight of the hind body rests on the heel pads, 
the pads at the metatarsophalangeal junction, and perhaps on the 
claws, which are usually spread slightly. The brachii are directed 
posterolaterally and dorsally and the forearms are directed an- 
terolaterally. If the body is not steeply inclined, the brachii are 
inclined up to 40 degrees above horizontal and inclined postero- 
laterally (Fig. 2B). The elbows are strongly flexed, and the fore- 
arms are oriented anterolaterally and inclined 50 to 60 degrees 
above horizontal. The thumbs are directed laterally, and the weight 
rests on the basal and distal thumb pads. 

If the body is inclined more steeply, the brachii are adducted 
but still directed strongly posteriorly. The forearms are extended 
slightly and oriented strongly anteriorly and slightly laterally. Pho- 
tographs of the bats in an inclined stance indicate that the first 
metacarpals are directed ventrally and the weight is concentrated 
on the distal thumb pads and phalanges, which are hyper-extended 
anteriorly and laterally from the metacarpal (Fig. 2C). 

When feeding terrestrially on the fetlock of a large ungulate, 
the bat assumes a posture that is similar to that of the elevated 
stance in Fig. 2C (Mitchell, 1970). The hind limbs are almost fully 
extended as in a jump, occasionally so much so that the weight 
rests on the pads at the metatarsophalangeal junctions. The brachii 
are adducted and oriented ventrally in a plane parallel to a sagittal 
plane through the body. The elbows are fully extended, and the 
forearms are directed nearly vertically. The thumbs are often ad- 
ducted in line with the long axis of the forearm, with the weight 



Altenbach — Vampire Locomotor Morphology 1 1 




Fig. 3. Hanging posture of Desmodus. 

resting on the terminal phalanges and claws as in Fig. 2C. The 
body is thus steeply inclined, and the lips can reach up to 8 or 10 
cm above the substrate. 

The transition from these postures, with the exception of the 
fully elevated feeding posture, to terrestrial locomotion is simple 
and involves only alternate strokes with the limbs. 



12 Spec. Publ. Amer. Soc. Mamm. 6 

Hanging Posture 

When a bat is fully alert and hanging on a vertical surface, the 
body is held as far as a centimeter away from the surface and is 
inclined anteroventrally with the head sharply turned upward or 
directed toward an observer (Fig. 3). The thighs are oriented lat- 
erally and shghtly dorsally, relative to the animal, and the shanks 
are flexed and directed upward, often slightly medially, and to- 
ward the vertical surface. The feet are oriented upward and the 
weight is on the claws which are slightly spread. The brachii are 
oriented posterolaterally at the level of midbody and the forearms 
are directed ventrolaterally. The thumbs are directed laterally or 
slightly dorsolaterally, with the weight supported by the basal pads 
and the claws. The inclination of the body and its position away 
from the surface tend to force the thumb toward the surface, using 
the hind feet as a fulcrum. This provides good traction for the 
forelimbs and allows sudden lateral or dorsal movements powered 
by the forelimbs. 

A resting position is similar, except that the body is close to the 
surface and the forelimbs are not directed laterally. When the bat 
is resting pendant from a steeply inclined overhead surface with 
sufficient irregularities to give the claws purchase, the hind limbs 
often are fully extended and the forelimbs are flexed toward the 
brachium and not in contact with the surface. However, when the 
animal is disturbed in this position, the hind limbs are flexed, draw- 
ing the body toward the surface, as the forelimbs are extended 
posteriorly or ventrally, relative to the bat, to bring the thumbs in 
contact with the surface. This allows the forelimbs to be used in 
an evasive drop into flight or terrestrial locomotion. 

Walking 

The walking gait of Desmodus on a horizontal surface, like all 
other locomotion in this species, is highly variable, the particular 
pattern depending upon a number of factors. When unhurried, 
bats accustomed to captivity and observation walk in a deliberate 
and even gait. However, under experimental conditions, this type 
of walking was infrequently observed; the animals usually em- 
ployed a faster walking gait. Analysis of films of slightly hurried 
locomotion of a bat approaching and starting up an inclined sur- 



AUenbach — Vampire Locomotor Morphology 13 

face indicates that at the start of a stride the hind limbs are flexed 
at the knee and oriented in reptilian fashion, with the plane of the 
limbs and feet directed posterolaterally (Fig. 4A). The brachii are 
inclined posterodorsally and the forearms are partially flexed, with 
the carpi and thumbs contacting the substrate roughly two cm lateral 
to the sides at midthorax. The body is about a centimeter above 
the substrate at the start of the stride. The hind limbs are extended 
at the knees as slight adduction of the brachii and extension of the 
right elbow lift the body and shift it to the left (Fig. 4B-C). Exten- 
sion of the left hind limb continues as the right hind limb is lifted 
by abduction of the femur and slight flexion of the knee and 
brought anteriorly (Fig. 4C-D). Almost concurrently the left fore- 
limb is lifted off the surface and extended forward and to the 
left (Fig. 4D). Within eight milliseconds the right forelimb is lifted 
after a lateral and posterior thrust and is brought forward by flex- 
ion of the elbow (Fig. 4D-F). Only the right hind limb remains in 
contact with the substrate, and extension of the right knee and a 
posterior swing of the femur provide forward thrust to the body. 
The right hind limb reaches the end of its forward swing and 
contacts the substrate as the left forelimb contacts the inclined 
surface toward which the bat is walking (Fig. 4F). Simultaneously 
the left hind limb is raised by abduction of the femur and begins 
a forward swing. Meanwhile, the left forelimb begins to pull the 
body forward and up the incline by movement of the brachium, 
which draws the distal end of the partially flexed forearm down- 
ward and posteriad (Fig. 4F-G). The right forelimb contacts the 
substrate, and extension of the forearm and slight adduction of 
the brachium drive the body forward and toward the incline (Fig. 
4H-I). The right hind foot is raised and swung forward as the bat 
pushes off the substrate with an extension of the left hind limb 
followed by a powerful adduction or flexion of the right thumb 
(Fig. 4I-K). As the right thumb is adducted, the left forelimb is 
lifted and the bat becomes airborne for about 10 milliseconds (Fig. 
4L-M). The right hind foot is extended laterally and ventrally to 
contact the substrate simultaneously with the left forelimb. The 
left hind limb reaches the end of its anterior swing and, with the 
knee flexed, contacts the inclined surface as the right forelimb 
contacts the substrate after flexion of the elbow to advance the 
arm. Both hind limbs extend, along with extension of the elbow 
and inclination of the brachium of the right forelimb, to thrust the 



14 Spec. Publ. Amer. Soc. Mamm. 6 



Jf^ J^ -4^ ^ -^ 



'j)-Ar-'^ 









Fig. 4. Drawings at 40 millisecond intervals of Desmodus walking rapidly on a 
horizontal surface (A-H) and up an incline (I-R). 



body up the incline, while the left forelimb is extended forward to 
grasp higher up (Fig. 4N-R). 

After the series of pictures upon which this description is based 
was taken, the bat executed a turn on the inclined surface and 
used the typical backward climbing method to climb it vertically. 

Hopping Locomotion 

When Desmodus further accelerates its movement on a horizontal 
surface, a hopping gait is employed, which leads to a rapid leaping 
type of locomotion if a sufficiently open expanse of substrate is 
available. Fig. 5A-E illustrates a turn prior to the initiation of hop- 
ping locomotion. The bat pivots to the right around the right hind 
foot by the force of the left forelimb pushing against the inclined 
surface immediately behind (Fig. 5A-C). The left hind limb is 
raised, pulled forward, and positioned lateral to the body (Fig. 5C- 
D). As the right forehmb is moved laterally during the last of the 
turn, the right hind limb is lifted slightly, and when the forelimb 
contacts the substrate, the right hind limb is powerfully extended 
(Fig. 5D-G). Both brachii are inclined and the forearms are ex- 
tended to drive the body forward and upward. The left hind limb 



Altenbach — Vampire Locomotor Morphology 15 



/^ Jk^" J'-f^ J^ I^ 




i). 



1^=^ \.^^ l4 



#^ ^ 




M NO P Q R 

Fig. 5. Drawings at 40 millisecond intervals of Desmodus in typical hopping 
locomotion on a horizontal surface. 



is raised as the right hind limb is extended, and both are pulled 
strongly forward. The forelimbs leave the substrate after the ter- 
minal adduction of the thumb for thrust and the bat is airborne 
for about 70 milliseconds (Fig. 5H-K). The forelimbs are then 
moved upward by adduction of the brachium and then anteriorly 
by simultaneous adduction, supination, and subsequent anterior 
swing of the brachii. The bat alights simultaneously on the antero- 
laterally directed hind feet and ventrally oriented thumbs (Fig. 
5L). 

Transition to a more vigorous hopping locomotion is accom- 
plished when the bat maintains forward momentum by inclination 
of the brachii and extension of the elbows (Fig. 5M-Q). The thighs, 
which were partially abducted as the bat alighted, are swung pos- 
teriorly, and the knee is extended to drive the body forward and 
upward, much as in a jump into flight. The hind feet leave the 
substrate as the forearms are extended (Fig. 5P-Q). A slight ad- 
duction of the brachii, with the forearms extended at right angles 
to them, provides upward momentum to carry the bat higher than 
in the previous hop. The thumbs are not forcefully flexed as the 
forelimbs leave the substrate, as in a typical jump. In addition, the 
weight is transferred from the thumb pads to the anterior surface 
of the carpi when the forelimbs are inclined. 



16 Spec. Publ. Amer. Soc. Mamm. 6 






^■:D| 







Fig. 6. Drawings at 44 millisecond intervals of Desmodus climbing on a vertical 
surface. Horizontal lines (1-5) on the surface behind bat are included as spacial 
reference points. 



Altenbach — Vampire Locomotor Morphology 17 

Hopping locomotion can carry the bat over a horizontal surface 
at rates of up to two m per second with surprising agility. The animal 
can readily hop over or around obstacles in its path with little 
noticeable reduction of speed. The hopping locomotion often al- 
ternates with short flights varying from slightly less than half a 
meter to several meters in length and 0.3 m or less in height. 
Often, only two or three hops are made between these flights. If 
there is an unobstructed path ahead of the bat, continuous forward 
flight is initiated by a more powerful jump. 

Climbing 

Although able to climb a vertical surface forward or sideways, 
Desmodus normally climbs backward, and, if hurried, slightly side- 
ways. I have observed this behavior in the wild as well as in the 
laboratory. The bats are exceptionally alert while climbing. The 
presence of an observer may influence the frequency of backward 
climbing, as this form of locomotion allows the bat a good view of 
the observer. Thus it is possible that when undisturbed, vampires 
may use other types of climbing. However, this seems unlikely. 
The following description of backward climbing is based on pic- 
tures of a subject climbing a vertical strip of 6-mm hardware cloth 
angled 25 degrees from parallel to the line of view (Fig. 6). 

A cycle begins with the left hind limb extended and grasping 
the wire (Fig. 6A). The right hind limb is flexed in a plane parallel 
to the wire after the. foot has released its grip through extension 
of the phalanges. The claws and basal and distal pads of the 
thumbs of both forelimbs are in contact with the wire. The right 
forelimb is slightly flexed and positioned anterior to the head while 
the left forelimb is strongly flexed and positioned caudad of the 
head. The left hind limb flexes at the knee and both forelimbs 
extend, driving the body upward while the right hind limb pulls 
away from the wire and reaches backward toward a higher grip 
(Fig. 6B-C). As the hind limbs are nearly side by side, the weight 
is transferred to both left limbs, and the right forelimb releases 
contact with a push that swings the body away from the wire (Fig. 
6D-F). (This maneuver was noted in nearly all of the motion pic- 
tures of climbing and may be the result of avoidance of the wire 
surface during movements of the limbs. The long, recurved claws 
of Desmodus are better suited for climbing on rough stone than on 



18 Spec. Publ. Amer. Soc. Mamm. 6 

screening where they easily become hooked over the wire strands.) 
The right brachium is pulled caudally and the forearm is flexed, 
thus lifting the right carpus to the level of the left. As the body is 
pulled toward the level of the left hind foot and shank, the right 
hind foot is fully extended and gains purchase on the wire as the 
right forelimb contacts it (Fig. 6E-G). Although the claws do not 
actually grasp the wire, the right forelimb provides support 
through contact of the thumb pads with it. Simultaneous flexion 
of the shanks of both hind limbs and a cranial and dorsal swing of 
the thighs lift the body, and the left forelimb releases its grip and 
is pulled upward by flexion of the elbow and upward rotation of 
the brachium (Fig. 6H-K). When the left forelimb contacts the 
wire, the left hind limb is released and extended upward, and the 
right forelimb is raised, as described for the left forelimb (Fig. 6J— 
M). Flexion of the right hind limb and extension of the right fore- 
limb lift the body, and the left hind limb is fully extended for a 
new grip (Fig. 6N). The left forelimb is raised by extension of the 
elbow to obtain a grip considerably lateral to the climbing path. 
When the left hind limb grasps the wire and begins flexion to raise 
the body, the right forelimb is flexed slightly at the elbow (Fig. 60) 
to give the thumb a grip higher on the screen. Its thumb is flexed 
to the level of the distal pad, which rests against the wire. From 
this position the bat assumes a horizontal resting posture against 
the wire (Fig. 6P-T). 

When vampires descend a vertical surface, the posture and ori- 
entation of the body are similar to those seen in climbing, and the 
movements are also quite similar. Although this behavior was ob- 
served on several occasions, it was not photographed for detailed 
analysis. The bats literally ran down the wire screen on the side of 
the flight compartment and could stop or change direction almost 
instantly, indicating sufficient contact of the limbs with the wire to 
allow control. 

Jumping Behavior 

The jumping behavior of Desmodus is perhaps the most striking 
and unique feature of its locomotion and is vital to the terrestrial 
feeding behavior of this genus. Although several other bats can fly 
from the ground, descriptions of this behavior (Eisentraut, 1936; 
Orr, 1954; Vaughan, 1959; Altenbach, 1968; Anonymous, 1969) 



Altenbach — Vampire Locomotor Morphology 19 




Fig. 7. Multiple exposure photograph of D esmodus ']um^mg into flight through 
an angle of about 60 degrees. 



20 Spec. Publ. Amer. Soc. Mamm. 6 




Fig. 8. High-speed photographs of Desmodus in the thrusting phase (A-E) and 
the coasting phase (F-H) of a jump into flight. 



Altenbach — Vampire Locomotor Morphology 21 




Fig. 9. High-speed photographs of Desmodvs in the last of the coasting phase 
(I-J) and the initiation of the first downstroke (K) following a jump into flight. 



indicate that flight is effected by an adduction of fully or partially 
extended wings or, on an open surface, by a series of these motions 
combined with several shallow hops to gain forward speed. Only 
Desmodus launches itself into flight almost vertically from a typical 
terrestrial stance with folded wings. Several authors (Ditmars and 
Greenhall, 1935, 1960; Dalquest, 1955; Leen and Novick, 1970) 
have commented upon the jumping behavior but none has de- 
scribed it in detail nor pointed out its significance. 

Recent investigations in Mexico (Robert Tigner, personal com- 
munication; Mitchell, 1970) and the observations of Hensel (1869) 
establish that Desmodus does feed from the ground at least occa- 
sionally and often moves about on the ground before and after 
feeding (Ditmars and Greenhall, 1960). Wimsatt (1969) reported 
that under natural conditions Desmodus often consumes more than 
50 per cent, and occasionally more than 100 per cent, of its body 



22 Spec. Publ. Amer. Soc. Mamm. 6 



^t ^ ^ 



A .000 B .020 C .040 D oeo 





E .080 F .092 G .104 




N .182 



O .208 



P .214 Q .226 



R .264 



Fig. 10. Drawings of Desmodus jumping into flight and corresponding elapsed 
time in seconds. 



weight in blood in a single feeding period. Thus, jumping behavior 
functions to get a heavily loaded bat into flight from a horizontal 
surface. In addition, this behavior probably enables the bat to avoid 
sudden movements of a large host animal that could crush a bat 
with its foot or to avoid a terrestrial predator such as a snake or 
carnivorous mammal. 

In the laboratory, it was difficult to photograph the bats jumping 
from an undisturbed walking gait or when startled from a typical 
terrestrial feeding posture. Thus the majority of the photographic 
records are of bats suddenly released from beneath a small enclo- 
sure. The photographs certainly show typical jumping behavior, 
especially hurried jumps, which probably are normal in avoidance 
reactions. 

Figure 7 is a multiexposure photograph of a vampire bat jump- 
ing into flight through an angle of approximately 60 degrees. It 
is included to give the reader a better perspective of the direction- 
ality and distance involved in a typical jump. The details are de- 
scribed below. 

Prior to a jump, Desmodus normally crouches with the body close 



Altenbach — Vampire Locomotor Morphology 23 

to the substrate (Figs. 8A, lOA). The brachii are highly abducted 
and inclined posteriorly five to 10 degrees above horizontal. The 
elbows are fully flexed, the forearms inclined about 15 degrees 
anteriorly and slightly laterally, and the thumbs directed laterally 
with the weight resting on the basal and distal pads. The thighs 
are abducted roughly 40 degrees above horizontal and directed 
slightly anterolaterally, laterally, or posterolaterally from the body. 
The knees are flexed between 90 and 120 degrees and the shanks 
are inclined posteriorly, posterolaterally, or occasionally postero- 
medially. The orientation of the hind feet varies between posterior 
and lateral with the toes slightly spread and the weight resting on 
the heel pads, the pads at the distal tips of the metatarsals, and the 
claws. The prejump position is variable, depending upon the na- 
ture of the substrate and how rapidly the animal initiates the jump 
from another posture such as walking or feeding positions. High- 
speed motion pictures indicate that the bats can jump short dis- 
tances from nearly any position, but when jumping into flight from 
a static position on a horizontal surface they usually assume a po- 
sition similar to that shown in Fig. 8A. 

The sequence of movements is highly variable, depending upon 
the angle of the jump, the plane of the substrate, the orientation 
of the bat on the substrate, and individual differences. In most of 
the high-speed photographs of bats jumping into forward flight 
from a flat, horizontal surface, the jump path was at an angle 
between 50 and 70 degrees above horizontal. The following de- 
scription of the movements involved in jumping into forward flight 
will emphasize this type of jump, which under experimental con- 
ditions appears to be the most frequently used. However, Desmodus 
is capable of jumping into flight through angles of 35 degrees to 
more than 80 degrees. Even in jumps that appear to be nearly 
identical, careful analysis of motion picture film reveals consider- 
able variation in the magnitude and temporal sequence of the var- 
ious movements. 

The jump is initiated by an inclination of the brachii and resul- 
tant declination of the highly flexed forearm (Figs. 8B, lOB-C). 
This movement shifts the center of gravity at midthorax in a line 
through the contact of the pectoral limbs and substrate and the 
direction in which the jump progresses. Extension of the hind 
limbs, which begins either a few milliseconds before or within 20 
milliseconds after the initiation of this movement, aids in the an- 



24 Spec. Publ. Amer. Soc. Mamm. 6 

terior shift of the body and supplies upward momentum to the 
posterior half of the body. As the brachii reach an inclination of 
between 40 and 55 degrees above horizontal, about 60 milliseconds 
after initiation of the jump, they are adducted to begin the upward 
thrust of the jump (Figs. 8B-C, lOC-D). Extension of the elbow 
normally begins concurrently or within two to five milliseconds after 
the adduction of the brachium, but if the jump is directed strongly 
anteriad, extension of the elbow precedes the adduction of the 
brachium by up to 10 milliseconds and increases the forward shift 
of the body. 

As the hind limbs reach almost full extension, the feet are ad- 
ducted to provide anterior and upward thrust to the body (Figs. 
8C, lOD). Because the center of gravity is positioned over the pec- 
toral limbs in hne with the angle of the jump, the last thrust from 
the hind limbs probably tends to stabilize the position of the body 
rather than supply much power to the jump. 

Adduction of the brachii and extension of the elbows continue 
about 20 milliseconds and accelerate the bat upward and forward. 
Although measurement of the movement of parts of the thorax is 
difficult from photographs of an animal covered with hair, depres- 
sion of the shoulder joint is evident during adduction of the hu- 
merus. This can be partially explained by the humerus being 
locked dorsally with the lateral scapular border as the lateral scap- 
ular border is rocked ventrad, but the depression appears more 
pronounced than would be accounted for by this movement. The 
frontal, still photographs of the jump illustrate this best and sug- 
gest that depression of the entire shoulder girdle occurs, which 
necessitates a ventral swing of the distal end of the clavicle (Fig. 
8B-E). The depression of the shoulder during adduction of the 
brachium would add to the upward momentum of the body and 
thus would certainly be advantageous in jumping. Although no 
direct evidence is available concerning the exact mechanism of the 
shoulder depression, analysis of the motion picture films indicates 
it does occur, and that it begins concurrently with adduction of the 
brachium and continues through all but the last few degrees of 
this movement. 

Between five and 15 milliseconds before the brachium is fully ad- 
ducted and the elbow is fully extended, flexion of the thumb begins 
(Figs. 8D-E, lOE). High-speed photographs show that the thumb 
remains relatively straight during adduction to provide a lever arm 



Altenbach — Vampire Locomotor Morphology 25 

of maximal length (Figs. 8E, lOE-F). The upward thrust provided 
by the movements of the body, brachium, and elbow is completed 
as the thumb leaves the substrate or within a few milliseconds be- 
fore; thus the thumb provides the last component of thrust in the 
jump. The contact with the substrate is broken when the thumb 
is adducted to within about 40 degrees of the long axis of the 
forearm. After adduction to this point, the forearm is raised almost 
imperceptibly, and the upward movement of the body facilitates 
the lift of the thumb off the substrate. Adduction of the thumb 
continues until it is parallel with the long axis of the forearm. This 
movement appears to have no function and is probably only a 
follow-through, as the thumb no longer meets resistance (Figs. 8F, 
lOG). 

Although there is considerable variation among the jumps re- 
corded on motion picture film, the velocity imparted to the body 
by the jump can readily be measured from the film. The highest 
velocity recorded as the bat broke contact with the substrate was 
2.4 m per second. In 10 other jumps into forward flight, the ve- 
locity varied between 1.3 and 2.2 m per second. Although jumping 
movements are used both in transition from terrestrial stance into 
flight, and in hopping terrestrial locomotion and avoidance move- 
ments, I did not attempt to calculate velocities imparted by jumps 
except those leading into flight. Simple calculation without consid- 
eration of air resistance indicates that an upward velocity of 2.4 m 
per second will carry an object to a height of about 30 cm. When 
compared with the motion pictures of the Desmodus jumping, this 
height seemed too great, but the bats normally jumped forward 
and upward at an angle of between 35 and 70 degrees above hor- 
izontal, thus much of the velocity imparted to the body was di- 
rected anteriorly. 

During the thrust phase of the jump, the long axis of the body 
is normally inclined upward between five and 20 degrees. The 
angle appears greater, as the head is often strongly upturned dur- 
ing the jump. The stability of the angle of the body indicates that 
the weight is effectively centered over the thrusting pectoral limbs 
and that perhaps the thrust from the pelvic limbs early in the jump 
counteracts forces that would incline the body. 

When the forelimbs leave the substrate, the powered phase is 
complete and a coasting phase begins with almost immediate flex- 
ion of the elbows (Figs. 8F-G, lOG-H). Abduction and supination 



26 Spec. Publ. Amer. Soc. Mamm. 6 

of the brachii and flexion of the elbows raise the forearms nearly 
parallel to a saggital plane through the body (Figs. 8F-H, lOG-I). 
As the forearms reach the level of the lower body, extension of the 
elbows and digits begins (Figs. 8H, 101). The abduction of the 
brachii continues, but the supination ceases as the forearms reach 
the level of the body. Thus the remainder of the wing positioning 
is a result of abduction and pronation of the brachii and extension 
of the forearms and digits. Figure 9I-K illustrates the remainder 
of the coasting phase and the beginning of the first downstroke. 

The angle of inclination of the body during this coasting phase 
of the jump is variable and seems directly related to the flight path 
during the first few wingbeats. The inclination is often as much as 
35 degrees during a coasting phase prior to the first wingbeats of 
climbing flight. Prior to and during the first wingbeat of nearly 
horizontal flight, the inclination of the body is reduced to orient 
the long axis of the body horizontally. This movement is easily 
explained by the rapid posterior and dorsal movement of the un- 
folding wings, which imparts a forward and downward force to 
the anterior body. 

The sequence of movements in a more vertical jump is different 
from those of an anteriorly directed jump. There appears to be 
little or no inclination of the brachii, and the jump is initiated by 
adduction of the brachii followed in roughly two to six milliseconds 
by extension of the elbows. Extension of the hind limbs starts about 
four to six milliseconds after adduction of the brachii and is directed 
downward, thus providing little or no forward momentum to the 
body. The forward thrust that is produced comes from the exten- 
sion of the elbows, since the brachii are oriented strongly poste- 
riorly during adduction. Adduction of the hind feet is similar to 
that seen in an anterior jump but provides primarily upward 
thrust, because the hind limbs are oriented ventrally instead of 
posteroventrally. Strong flexion of the thumb is initiated prior to 
the completion of brachial adduction and extension of the elbow 
to provide the last upward thrust. It appears that a jump forward 
and upward provides more upward momentum and is better suit- 
ed to initiating flight from the ground than is a laterally or pos- 
teriorly directed jump. A rapid turn made immediately after the 
jump is usually used in favor of a jump directed laterally. 

Lateral and posterior jumps are typically used in avoidance re- 
actions, particularly if the bat is not oriented toward an open flight 



u*. 



A .000 



H .117 



Altenbach — Vampire Locomotor Morphology 27 



M. n 




B .020 



C .035 



D .050 E .070 



F .092 



J .14 2 



K .152 



L .162 



G .102 




M .172 



Fig. 11. Drawings of Desmodus performing an anterolateral jump and turn into 
horizontal flight. Numbers are elapsed time in seconds. 



path that would allow a forward jump into flight. Most of the 
lateral and posterior avoidance jumps were recorded only on high- 
speed still photographs, which prevents detailed description of the 
movements involved. However, one motion picture sequence of an 
anterolateral jump was obtained. In this sequence, the hind limbs 
initially shift the center of gravity slightly forward and laterally 
into the line of the jump over the pectoral limbs. The major thrust 
of the hind limbs, however, is almost vertical. Because the body is 
accelerated laterally, the vertical thrust component of the hind 
limbs imparts a yaw to the body so that its long axis swings per- 
pendicular to the prejump axis (Fig. IID-E). The body appears 
shifted to the left by shght flexion of the left elbow toward the 
inclined brachium (Fig. IIA-C). Adduction of the right brachium 
and extension of the right elbow begin and continue to shift the 
body, and thus the center of gravity, laterad over the left forelimb 
(Fig. 11 D). Adduction of both brachii and extension of the elbows 
now thrusts the bat upward, slightly forward, and strongly to the left 
(Fig. IIE-F). The flexion of the right thumb and simultaneous pos- 
terior swing of the right forearm swing the long axis of the body to- 
ward a position perpendicular to its prejump axis. Flexion of the left 
thumb supplies the final upward thrust (Fig. IIG). During the 
coasting phase, the momentum imparted by the right limb swings 
the body perpendicular to the prejump position (Fig. IIH-M). 

A single high-speed photograph of a posterior jump (Fig. 12) 
indicates that the hind limbs impart slight upward and backward 



28 Spec. Publ. Amer. Soc. Mamm. 6 




Fig. 12. High-speed still photograph of Desmodus 100 milliseconds after initia- 
tion of a posterior jump. 



momentum by extension of the knees and adduction of the thighs. 
The pectoral limbs are probably adducted and extended from the 
prejump posture with no prior inclination of the brachium, as the 
extended limbs are seen to be thrust strongly anteriad at the instant 
of the exposure, about 100 milliseconds after initiation of the 
jump. It appears improbable that flight could be initiated from a 
jump of this type, as it did not progress more than a few centi- 
meters vertically and thus would not allow for a full downstroke, 
although a rolling maneuver could perhaps orient the body in the 
opposite direction. Jumps such as this are obviously necessary to 
avoid sudden movements of a host animal, obstacles the host ani- 
mal brushes by, or predators the bat might encounter on the 
ground. Flight could readily be initiated after a posterior jump by 



Altenbach — Vampire Locomotor Morphology 29 




Fig. 13. Drawings of Desmodus jumping into flight from a walking gait: A-D, 
10 millisecond intervals; D-E, 8 millisecond intervals; E-G, 6 millisecond intervals; 
G-J, 4 millisecond intervals; J-N, 8 millisecond intervals. 



alighting, executing a partial turn, and then jumping anterolat- 
erally or forward. 

Figure 13 illustrates a jump into flight following the completion 
of a stride at a walking gait. As the left forelimb contacts the sub- 
strate after a forward swing (Fig. 13 A-D), simultaneous brachial 
adduction and extension of the hind limbs thrust the body forward 
and upward (Fig. 13E-N). The thumbs supply the final upward 
thrust typical of jumps initiated from a stationary position. 

Desmodus uses the jump to initiate flight from a vertical roosting 
surface or from the side of a host animal. In the prejump posture 
on a vertical surface, and brachii are nearly parallel with the long 
axis of the body, and the forearms are partially extended with the 
thumbs oriented dorsally and laterally against the surface (Fig. 
14A). The hind limbs, which support much of the weight, are held 
with the knees slightly flexed. The jump is initiated by adduction 
of the brachii and extension of the forearms with no preliminary 
inclination of the brachii (Fig. 14B-D). Because the hind feet retain 
their grip on the surface for a few milliseconds, the thrust of the 
pectoral limbs sharply inclines the body relative to the vertical sur- 
face. The momentum imparted by this movement orients the long 
axis of the body horizontally in the coasdng phase of the jump. As 



30 Spec. Publ. Amer. Soc. Mamm. 6 



.A 








€^ 





O p Q 

Fig. 14. Drawings at 12 millisecond intervals of Desmodus in a jump into flight 
from a vertical surface. 



the adduction of the brachii and extension of the forearms pro- 
gress, the hind limbs release the surface and the body is thrust 
laterad and slightly ventrad (Fig. 14D-E). The thrust is completed 
by extension of the thumbs as in a jump from a horizontal surface 
(Fig. 14E-F). The elbows remain extended, and the wings are po- 
sitioned for the downstroke by abduction of the brachii and ex- 
tension of the digits as the long axis of the body becomes nearly 
horizontal (Fig. 14G-K). As the airspeed is high because of the 
lateral thrust of the jump, a downstroke of high amplitude is ap- 
parently not necessary and the wings are abducted only 20 degrees 
above horizontal prior to the first downstroke, which is similar to 
one seen in level forward flight several wingbeats after a jump 
from a level surface (Fig. 14L-Q). 



Altenbach — Vampire Locomotor Morphology 31 

Initial Flight Following a Jump 

In initial flight following a jump, the position of the body, move- 
ments of the wings, and direction of the flight path are variable 
and, as in other types of locomotion, are dependent upon many 
factors. A description of the movements recorded on a single high- 
speed motion picture film would not adequately cover this aspect 
of locomotion. Still photographs and drawings from films of sev- 
eral different flights will be discussed in an attempt to describe at 
least most of the characteristics of the flick of Desmodus. 

When jumping into flight from the ground, Desmodus does not 
have the advantage of species that begin flight from a high roost 
and can build airspeed by a vertical drop or by a shallow dive 
during the first few wingbeats (Eisentraut, 1936; Vaughan, 1959, 
1970^; Hayward and Davis, 1964; Altenbach, 1968). Although 
some other bats can take flight at a steep angle from a horizontal 
surface, the majority of these have light wing loading or complex 
modifications of the wingbeat cycle that allow hovering. Desmodus 
is heavily loaded (Struhsaker, 1961; Hartman, 1953), and my in- 
vestigation revealed no extreme wingbeat modifications typical of 
heavy-bodied, hovering species (Altenbach, 1968). The only for- 
ward airspeed available to Desmodus after a jump is provided by 
the momentum of the jump. 

During photography of jumps into flight, bats normally did not 
fly higher than 0.3 to 0.6 m above the level of the surface from 
which they jumped. Thus the flight path was usually inclined no 
more than 15 degrees above horizontal, although in a few instances 
bats flew upward at an angle of 60 or 70 degrees above horizontal. 
When released on the laboratory floor, Desmodus typically jumped 
from the floor and flew within less than a meter of it for as far as 
10 m. Dalquest (1955) and Wimsatt (1959) commented that Des- 
modus flies within a meter of the ground. 

Coasting phase and initial flick. — In a jump into a forward flight 
with a climb path of five to 10 degrees (Fig. 15), the body is slighdy 
inclined during the coasting phase. As the wings are abducted to 
the level of the body (Fig. 15G-I), within about 100 milliseconds 
of initiation of the jump (Fig. 151), the forward motion imparted 
by the jump is only about 0.2 m per second. However, as the 
forearms and digits are extended and the wings are abducted, the 
distal half of the wings assumes a configuration that provides for- 



32 Spec. Publ. Amer. Soc. Mamm. 6 





'^ 



<S7^ 




J^ 





Fig. 15. Drawings at 20 millisecond intervals of Desmod-us in a jump into nearly 
horizontal flight. 



ward thrust (Fig. 15I-J). As extension of the wings begins, the 
digits are inclined posteroventrally between 60 and 80 degrees 
below horizontal. In the next 30 milliseconds, the digits are fully 
extended and inclined posteriorly through an arc of roughly 70 
degrees, as the wings are raised 50 to 60 degrees. The movement 
of the distal half of the wings is rather complex and is the result 
of several movements of the arms and hands. Extension of the 
digits and extension of the forearms impart a rapid lateral move- 
ment to the wingtip. Abduction of the arm adds a vertical com- 



Altenbach — Vampire Locomotor Morphology 33 

ponent to this movement, and pronation of the arm and extension 
of the phalanges add a posterior component. Through the first 
half of this movement, while the digits are still directed strongly 
ventrally, the distal half of the chiropatagium attains velocities of 
11 to 12 m per second. During this phase, the average forward 
velocity of the bat increased from 0.2 m per second to 0.56 m per 
second, indicating that forward thrust was being produced. In de- 
scriptions of forward and hovering flight in other species of bats, 
Eisentraut (1936) and Norberg (1970a) indicated that, in the last 
phase of the upstroke, similar movements produce strong forward 
thrust. 

As the wing reaches a fully abducted position prior to the initi- 
ation of the downstroke (Fig. 15J-K), decreased velocity at the 
distal chiropatagium probably reduces forward thrust. 

First downstroke. — The transition from upstroke to downstroke is 
not clearcut, but is marked by a progressive change in the direction 
of movement. At peak upstroke the wings are positioned about 60 
degrees above horizontal and full extension of the digits has ori- 
ented the distal plagiopatagium and all but the trailing edge of the 
chiropatagium almost behind the leading edge (Fig. 15K). The 
terminal phalanges of digits III, IV, and V still are slightly flexed 
ventrally from the dorsal air pressure during abduction, thus the 
trailing edge of the chiropatagium is below the plane of the rest 
of the wing. The hind limbs are fully extended posterior to the 
body and parallel with its long axis. 

The downstroke begins with a slight anterior swing of the brachii 
(Fig. 15L) accompanied by adduction and pronation of the arms. 
This movement depresses the leading edge of the wings and elim- 
inates the ventral flexion of digits IV and V. Eisentraut (1936) 
maintained that complete extension of the phalanges of digits IV 
and V is the result of air pressure against the membrane adjacent 
to them. However, analysis of several high-speed motion picture 
films of the start of the downstroke leads me to believe that, al- 
though adduction of the wing is evident and air pressure from 
below contributes to this movement, an active dorsal extension of 
the digits also is involved. The movement of the wing is slight as 
the phalanges are rapidly extended. There appears to be no pro- 
nounced dorsal billowing of the chiropatagium between digits III, 
IV, and V as would be expected if the force of the air were causing 
the movement of the phalanges. As adduction of the wings pro- 



34 Spec. Publ. Amer. Soc. Mamm. 6 

gresses ventrally and slightly anteriorly, the arms remain strongly 
pronated. The pronation and the force against the air below the 
wings cause the trailing edges of the distal half of the plagiopata- 
gium and the chiropatagium to be about 10 degrees above the 
leading edges (Fig. 15L-M). This portion of the wings is thus in 
a thrusting configuration, as the air is readily accelerated poste- 
riorly to impart a forward component of force to the wing, as 
described by Eisentraut (1936) for this phase of the wingbeat in 
forward flight of other bats. The leading edge of the chiropata- 
gium, or digits II and III, is depressed relatively more than the 
membranous propatagium because of the strong pronation of the 
brachium. Even when the limb is in a fully extended position, the 
long axis of the forearm is angled between 30 and 40 degrees 
ahead of the axis of the brachium; thus pronation of the brachium 
imparts a ventral swing to the distal forearm and anterior digits 
(Fig. 15M). Air pressure tends to bend the phalanges of digit IV 
dorsad thus adding to the thrusting configuration of the wing. The 
dorsal bending of the fourth digit to produce the thrusting of the 
distal chiropatagium is described by Vaughan (1959, 1970c?, 
1970^), who estimated that in the species of bats he studied no 
more than 20 per cent of the wing produced thrust during any 
phase of the wingbeat cycle (Vaughan, \910d). It is evident from 
analysis of the motion pictures of Desmodus in flight that probably 
60 to 80 per cent of the wing provides thrust. This thrust is greater 
distally than proximally because of the greater angle of anteroven- 
tral inclination of the chiropatagium and the more rapid move- 
ment of the wing distally. The extremely large part of the wing 
producing thrust is probably necessitated by the high wing loading 
in this species coupled with the habit of taking off from the ground 
where high thrust is vital to gain sufficient airspeed for more ef- 
ficient flight. 

The hind limbs are depressed concurrently with, or slightly later 
than, the adduction of the brachii and thus depress the trailing 
edge of the plagiopatagium, which in turn shapes the medial half 
to one quarter of the plagiopatagium into a more cambered surface 
than at the start of the downstroke. 

Superimposition of successive motion picture frames of the 
coasting phase of a jump and the first wingbeat indicates that, prior 
to the beginning of the downstroke, the upward velocity has 
dropped to about 0.3 m per second although the forward speed 



Altenhach — Vampire Locomotor Morphology 35 

has been increased by the flick phase of the upstroke. By the end 
of the first half of the downstroke, upward velocity of the body 
increases to an average of 0.5 m per second indicating production 
of lift. Forward velocity also increases, indicating production of 
thrust during the downstroke. The magnitude of this acceleration 
was not calculated because the bat was flying toward the camera. 
Direct observation of the motion pictures projected at 16 frames 
per second shows a definite upward "hop" of the bat during the 
first downstroke. The amplitude of the hop varied between dif- 
ferent films but was as great as 12 mm during the first half of the 
stroke. This hop is equally evident in flights where the forward 
speed at the start of the downstroke was extremely low (about 0.1 
m per second). It seems obvious that an upward and forward ac- 
celeration of the bat results from a downward and backward ac- 
celeration of air as the wings are swept through the downstroke. 

From the level of the body, the path of the downstroke becomes 
increasingly more anterior. The arms remain strongly pronated as 
the wings are adducted past the level of the body, but as they reach 
an angle of approximately 30 degrees below a horizontal plane 
through midbody, the pronation is lessened (Fig. 15N). The up- 
ward bending of the phalanges of digit IV continues, although the 
anteroventral inclination of the leading edge is reduced. The up- 
ward deflection of digit V is eliminated by flexion of the phalanges, 
thus increasing supination of the wing, and continuous depression 
of the hind limbs depresses the trailing edge of the entire plagio- 
patagium below the leading edge of the wing. Air acceleration 
during this phase of the stroke would be strongly downward and 
would supply a component of high lift. 

As the wings reach an angle of roughly 50 degrees below hori- 
zontal, the adduction of the brachii is almost stopped and a flexion 
of the forearms and pronounced supination of the arms begin 
(Fig. 15N-0). This movement strongly supinates the distal half of 
the wings and swings them anteriad and mediad. The air accel- 
eration from the more medial portions of the wing is directed 
somewhat downward by these movements thus producing more 
lift and thrust while air acceleration from the chiropatagium still 
produces thrust. 

Upstroke and flick. — There is no sudden transition into the up- 
stroke, rather a uniform transition to a different direction of move- 
ment. As the opposing planes of chiropatagii become parallel, con- 



36 Spec. Publ. Amer. Soc. Mamm. 6 

tinuing flexion of the forearms and supination of the brachii lift 
them vertically in this position (Fig. 150) toward the level of the 
body. The digits remain fully extended during this movement and 
the vertical orientation of the entire chiropatagium and much of 
the distal plagiopatagium keeps the air resistance to this movement 
minimal. 

Abduction of the brachii begins with the vertical movement of 
the forearms and occurs simultaneously with abduction of the hind 
limbs. The elastic properties of the plagiopatagium, and perhaps 
also contraction of the M. coraco-cutaneous, appear to reduce its size 
when the wings are in an anterior position and probably help to 
reduce drag. The hind limbs maintain tension posteriorly to stretch 
the membrane and prevent it from flapping from the forward 
motion of the body. Since the bat is rapidly accelerating during 
the first few wingbeats, reduction of drag is vital. 

There is considerable flexion of the phalanges of digits III, IV, 
and V during this phase of the stroke, probably the result of sud- 
den loss of pressure against the ventral surface of the chiropata- 
gium and distal plagiopatagium while this membrane is raised ver- 
tically. Considerable flexion of the digits (metacarpals) toward the 
forearm also occurs during the last phase of this part of the stroke. 
Flexion of the phalanges at this stage is of functional importance 
since their extension during the next stage provides increased 
thrust. 

As abduction and supination of the brachii raise the carpi above 
the level of the body, extension of the forearms begins. Extension 
of the forearms and digits and abduction of the brachii swing the 
chiropatagii first laterally and then posterodorsally (Fig. 15P). The 
posterodorsal swing is exaggerated by a pronation of the brachii 
when they reach their highest angle of inclination (Fig. 15Q). This 
is the thrusting phase described in the upstroke of other species 
of bats by Eisentraut (1936) and Norberg (1970a), who termed it 
the "flick phase." As the chiropatagium is extended, supinated, 
and abducted from a vertically oriented position anterior to the 
head, its movement against the airstream imparts a large compo- 
nent of forward thrust to the wings. 

There is extreme variation in the first wingbeat cycle, and the 
above description pertains only to flight that is nearly horizontal. 
Frequently the digits are not fully extended at the beginning of 
the downstroke and the phalanges of digit III remain flexed at the 



jf^ 



Altenbach — Vampire Locomotor Morphology 37 




13^ 






V 





-c? 



s 





?fsr 





(rw 



rCP^ < 






w 





BB 



~y< 



^-. 



^■/= 





cc 



Fig. 16. Drawings at 15 millisecond intervals of Desmodus in a jump into flight 
with the digits not fully extended. 



38 Spec. Publ. Amer. Soc. Mamm. 6 

TABLE 1 
Relative Lengths of Time (in Seconds) of Phases of Wingbeat Cycles of 
Desmodus rotundus Following a Jump into Flight in Five Trials of Individuals. 
Abbreviations: L Initial flick; D, Downstroke; U, Upstroke prior to Flick; 

F, Flick. 



Wingbeat 
number 


Phase 






Trial number 






1 


2 


3 


4 


5 




I 


.030 


.048 


.036 


.040 


.038 


1 


D 


.052 


.040 


.048 


.048 


.052 




U 


.020 


.020 


.024 


.024 


.024 




F 


.018 


.022 


.024 


.018 


.028 


2 


D 


.048 


.054 


.050 


.048 


.056 




U 


.014 


.028 


.026 


.026 


.022 




F 


.022 


.016 


.020 


.018 


.018 


3 


D 


.052 


.058 


.052 


.050 


.050 




U 


.014 


.020 




.020 


.018 




F 


.026 


.018 




.018 


.020 


4 


D 

U 
F 


.058 
.020 
.024 











second and third interphalangeal joints. This illustrates the im- 
portance of the thrust produced by the medial chiropatagium and 
distal plagiopatagium as the leading edge of the wing is declined 
below the trailing edge. The view that thrust is produced only by 
the propeller configuration of the distal chiropatagium between 
digits III and IV as the phalanges of digit IV bend upward ob- 
viously does not apply to the initial flight of Desmodus. Figure 16 
illustrates this in a bat jumping into a flight path that is inclined 
upward about 10 degrees. The upward and forward momentum 
imparted by the jump was low and the bat initiated flight with an 
air speed of about 0.2 m per second. The first downstroke starts 
with the digits partially extended from the forearm and the pha- 
langes of both third digits flexed in a configuration typical of a 
folded wing (Fig. 161). Because the bat is flying toward the camera, 
the forward speed is nearly impossible to calculate without complex 
photogrammetric procedures. However, forward acceleration was 
reflected in the increasing size of the image of the bat on the film. 
The drawings in Fig. 16 all are to the same scale and do not reflect 
increasing size of the photographic images. The digits are not fully 
extended until the last of the third wingbeat cycle (Fig. 16CC), yet 



Altenbach — Vampire Locomotor Morphology 39 

prior forward acceleration (Fig. 16G-CC) indicates thrust was pro- 
duced. The propeller configuration of the chiropatagium noted 
above, and described earlier by Vaughan (1959), was certainly not 
possible, thus thrust was probably produced by the distal portion 
of the plagiopatagium and the proximal portion of the chiropa- 
tagium during the downstrokes. No doubt the initial flick and the 
flicks in the subsequent wingbeat cycles produced additional thrust. 

Time periods for the initial flick and for portions of initial wing- 
beat cycles in several flights are presented in Table 1. Although 
there is considerable variation between flights, it is evident that the 
initial flick, because of its greater amplitude, lasts longer than sub- 
sequent flicks and provides thrust over a longer period. The up- 
strokes (including the flick) require less time than the downstrokes, 
as Eisentraut (1936) described for other species, and reflect the 
low resistance of the wing against the air stream initially, and the 
rapidity of the flick. 

Steeply inclined flight and turning maneuvers. — If the flight path is 
inclined steeply upward or if the bat executes a relatively sharp 
turn during the first few wingbeats after a jump, the angle of the 
long axis of the body is usually steeply inclined during the coasting 
phase of the jump and initial wingbeats. Figure 17 illustrates a 
jump from an inclined surface and an immediate right turn into 
nearly level flight. Both upward and forward velocities were low 
(about 0.2 m per second) at the start of the initial flick. The body 
is inclined upward at about 60 degrees during the coasting phase 
of the jump and remains in this attitude during the entire turn. 
The flick progresses as described above, but the inclination of the 
body directs more of the air acceleration downward thus providing 
both upward and forward acceleration to the body (Fig. 17I-K). 
The downstroke is similar to the one described above and is char- 
acterized by strong pronation that orients the leading edge of the 
wing approximately 20 degrees below the trailing edge over the 
distal two-thirds of the plagiopatagium and entire chiropatagium. 
The inclination of the body directs much of the air acceleration 
downward, thus supplying high lift and upward momentum. The 
downstroke progresses far ventrally, relative to the bat, apparently 
to provide air acceleration for a relatively longer time than in hor- 
izontal flight after a jump (Fig. 17L-M). The bat has jumped into 
a virtual stall and needs all possible downward air acceleration to 
remain airborne. The turn is initiated at the flick phase of this 



40 Spec. Publ. Amer. Soc. Mamm. 6 




Fig. 17. Drawings at 20 millisecond intervals oi Desmodus in a jump into steeply 
inclined initial flight. 



wingbeat, but the unilateral differences that effect the turn are 
subtle. In another series of drawings of a turn following a jump, 
the right hind limb is depressed far below the left early in the first 
two downstrokes (Fig. 18I-J, 180-P). This provides greater drag 
on the right side of the body as well as reduced thrust resulting 
from reduction of the area of the wing oriented to provide thrust. 
The resultant differences in forward velocity of the wings appar- 
ently produce a right turn. The upstroke effects a horizontal ori- 
entation of the body, and the flight progresses horizontally at near- 
ly a right angle to the direction of the jump (Fig. 18R-U). 

In flight inclined at greater angles, the wing movements are 
similar but the inclination of the body is greater. High amplitude 
downstrokes occur at about the same angle relative to the bat, but 
the resultant air acceleration is directed downward to provide up- 
ward momentum. 



Altenbach — Vampire Locomotor Morphology 41 



1> i> 4^ -f^ f ? '"i 



J 



If" 






Fig. 18. Drawings at 20 millisecond intervals of Desmodus in a jump into flight 
followed by a turn during the first two wingbeats. 



Slow Forward Flight 

High-speed still photographs (Figs. 19, 20) taken from the side, 
about four to eight wingbeats after a jump into horizontal flight, 
illustrate changes that occur in the wingbeat cycle and show rather 
subtle features of the wings that are not apparent in the motion 
pictures. This series of pictures was selected from nearly 300 still 
photographs of flight sequences of different individuals to best 
illustrate particular features of the wingbeat cycle. 



42 Spec. Publ. Amer. Soc. Mamm. 6 




Fig. 19. High-speed still photographs of stages in the downstroke of Desmodus 
in slow, forward flight. 



After the first four to eight wingbeats in level flight the bat has 
accelerated to about 2 m per second and its aerodynamic require- 
ments have changed somewhat from those in the wingbeats im- 
mediately following a jump into flight. The bat is still accelerating 
to a flight speed that is typically over 5 m per second and the 



Altenbach — Vampire Locomotor Morphology 43 

wingbeat must still produce lift and thrust. However, the bat has 
the advantage of air speed that will allow the deflection of air by 
the wings as the bat passes through it. 

Downstroke. — At the start of the downstroke the strong pronation 
characteristic of the beginning of adduction is evident (Fig. 19A). 
As the downstroke progresses, pronation of the entire arm is evi- 
dent, and an upward deflection of the terminal two bony phalanges 
of digit III and the phalanges of digits IV and V can be seen (Fig. 
19B-C). This upward deflection is the result of the upward pres- 
sure of air as the wing is adducted and perhaps contraction of the 
phalangeal extensors as well. The deflection is most obvious in 
digits III and IV (about 30 degrees above the long axis of the 
metacarpals) and only slight in digit V (about eight degrees above 
the long axis of metacarpal V). The upward deflection of the pha- 
langes of digit V appears unique and has not been described for 
any other bat. This configuration increases the posterodorsal in- 
clination of the medial wing and, along with the upward billowing 
of the distal half of the plagiopatagium, produces a thrusting sur- 
face for this part of the wing. The upward deflection of digit IV 
is typical of all bats during the downstroke, and serves primarily 
to increase the upward inclination of the chiropatagium between 
digits III and IV to provide a high thrust component, as this part 
of the wing is adducted at a higher velocity than the more medial 
parts of the wing. The upward inclination of the phalanges of digit 

III is more difficult to explain functionally. It reduces the forward 
thrusting capabilities of the distalmost part of the wing and directs 
forces on the membrane between the phalanges of digits III and 

IV medially, rather than anteriorly, as exhibited in other species 
of bats (Eisentraut, 1936; Vaughan, 1959, 1970^, 1970^; Alten- 
bach, 1968). Due to the posterior curve of the distal part of the 
leading edge of the chiropatagium and the strong pronation of the 
arm, low resolution photographs of the bat flying toward the cam- 
era do not show this condition, although it may be present. Al- 
though this configuration of the distal wing is perhaps important 
in providing lift later in the downstroke, it may function at this 
stage to alter the tip vortex. The bat has an air speed of about 2 
m per second at this time, and certainly tip vortices could alter 
airflow characteristics across more medial parts of the wing. Des- 
modus has an extremely high wing loading and does not have a 
long wing to displace the tip vortices distally as do some of the 



44 Spec. Publ. Amer. Soc. Mamm. 6 

equally heavily loaded molossid bats, such as Eumops perotis and 
Tadarida molossa (Vaughan, 1959, 1966), and Molossus ater (Hart- 
man, 1963). Other means of reducing the vortices may be essential 
in Desmodus. Photographic evidence for heavily loaded, low aspect 
ratio bats like Artibeus jamaicensis would be interesting to analyze 
to see if this phenomenon also occurs in them. 

As the wing is adducted to the level of the body, the dorsal 
deflection of phalanges of digit V is first reduced and then elimi- 
nated by ventral flexion (Fig. 19D-E). Adduction of the hind leg 
during this stage depresses the trailing edge of the plagiopatagium 
and increases the camber to deflect and accelerate air downward 
to provide an increasing component of lift (Fig. 19D-F). As the 
wing is adducted below the body (Fig. 19F-G), flexion of the pha- 
langes of digit V becomes more pronounced and, along with con- 
tinued adduction of the hind limbs, increases the camber and angle 
of attack of the entire plagiopatagium and medial half of the chi- 
ropatagium between digits IV and V. The phalanges of digits IV 
and III remain deflected upward to maintain the thrusting con- 
figuration of the lateral chiropatagium between the phalanges of 
digits V and IV, and of all the surface between the phalanges of 
digits III and IV. As the stroke progresses anteriad and ventrad, 
the configuration of the lateral chiropatagium that produces pos- 
terior air acceleration and thrust in the middle of the downstroke 
now produces increasing lift generation from this portion of the 
wing (Fig. 19H-I). 

Upstroke and flick. — The flexion of the forearms approximates 
the distal plagiopatagii and chiropatagii as described in initial 
flight, and supination and abduction of the brachii raise the fore- 
arms, and thus the vertically oriented wings, parallel and anterior 
to the body (Fig. 20J-L). The smooth transition from downstroke 
to upstroke by an anterior and medial movement of the wings is 
important for two reasons. First, this type of transition allows for 
a wing configuration that permits a thrust and lift generating 
movement during the upstroke. Second, the waste of muscular 
effort to reverse direction of movement is reduced by a transition 
involving only gradual change of configuration and direction of 
movement. At the level of the upper body, flexion of the digits is 
noticeable (Fig. 20M), and the flick phase is initiated by extension 
of the forearm and digits, and by abduction and pronation of the 
arm at the brachium (Fig. 20N-O). The phalanges of digits III, 



Altenbach — Vampire Locomotor Morphology 45 




Fig. 20. High-speed still photographs of stages in the upstroke and flick of 
Desmodus in slow, forward flight. 



IV, and V remain ventrally flexed during this rapid movement 
and help maintain an efficient thrusting surface. Although Eisen- 
traut (1936) described this flick phase in detail and suggested it 
provided a strong forward thrust, it has not been credited with 
providing thrust by more recent investigators of bat flight. Most 
other descriptions of bat flight, except that of Eisentraut (1936), 
imply that the upstroke in bats is typically a recovery stroke, as it 
is in most birds (Storer, 1948), and provides no forward thrust. 
The strongest evidence that the flick phase actually produces thrust 



46 Spec. Publ. Amer. Soc. Mamm. 6 

is the acceleration seen during the flick phase prior to the initial 
downstroke after a jump into flight described earlier. The still 
photographs illustrate the ventral and anterior billowing of the 
chiropatagium between digits III, IV, and V (Fig. 20O) as the 
chiropatagium swings laterad, posteriad, and dorsad. Similar bil- 
lowing of the plagiopatagium immediately medial to digit V of the 
chiropatagium and between the phalanges of digits V, IV, and III 
is evident in Fig. 20P-Q, indicating that an anterior force is gen- 
erated here by the pressure of the airstream. The billowing of the 
patagii anteriorly, the rapidity of the movements of the flick phase, 
and the acceleration evident during a similar movement after a 
jump provide convincing evidence that considerable forward 
thrust is produced. 

Motion picture data on slow forward flight. — A series of drawings 
from motion picture film taken of the third and the beginning of 
the fourth wingbeat after a jump into horizontal flight further 
illustrates some of the features considered previously (Fig. 21). 
The pronation at the first of the downstroke is seen at A and B. 
The leading edge of the wing at the level of digit V is depressed 
fully 15 degrees below the trailing edge. Although not visible, the 
phalanges of digit V are probably deflected upward, because the 
upward deflection of the phalanges of digits III (second and third 
phalanges), and IV can readily be seen in the right wing (Fig. 2 IB). 
As the wing is adducted, the effect is no longer obvious, illustrating 
that the angle of the wing relative to the camera can easily obstruct 
the view of critical details of the flight mechanism. In Fig. 21D-H, 
the adduction is clearly seen as is a decrease in pronation and 
increase in medial camber accompanying depression of the hind 
limbs during the last half of the downstroke. Flexion of the fore- 
arms (Fig. 21G-I) brings the wing medially and strongly anteriorly. 
The flick phase is initiated at Fig. 21J and terminates about 22 
milliseconds later between M and N. Fig. 21N-Q shows the begin- 
ning of adduction and pronation of the wing and establishment of 
the upward deflection of the phalanges of digits III and IV. 

Although they do not show the upward deflection of the pha- 
langes of digit V, drawings of frames of motion picture film taken 
from the side of a bat in forward, horizontal flight at about 2.5 m 
per second show the upward deflection of the phalanges of digits 
III and IV, the purely ventral movement of the strongly pronated 
wing to the level of the body, and the decrease in pronation after 



AUenbach — Vampire Locomotor Morphology 47 





tj^ "^y 



i^-^ 



'C^.. 












Fig. 21. Drawings of a head-on view of Desmodus in slow forward flight. Time 
intervals (milliseconds) between successive positions are: A-B, 6; B-C, 12; C-D, 8; 
D-E, 8; E-F, 8; F-G, 10; G-H, 8; H-I, 6; I-J, 6; J-K, 8; K-L, 6; L-M, 6; M-N, 
4; N-O, 2; O-P, 2; P-Q, 6. 



48 Spec. Publ. Amer. Soc. Mamm. 6 







^3 ^v, 



F G -^ H '<-! V\ % J 







P 






i3 





S T U 

Fig. 22. Drawings at 5 millisecond intervals of a side view of Desmodus in slow, 
forward flight. 



Altenbach — Vampire Locomotor Morphology 49 

that point (Fig. 22A-G). It is certainly possible that at this airspeed, 
the upward deflection of the phalanges of digit V may be oblit- 
erated or prevented in the early downstroke by phalangeal flexors. 
Sufficient thrust may be generated by posterior air acceleration 
from more distal parts of the wing, and it may be advantageous to 
maintain a cambered medial wing to deflect air downward and 
produce lift. In the last part of the downstroke, the wing is oriented 
more anteriorly and adducted to about 70 degrees below horizon- 
tal. The deep amplitude of the downstroke seems characteristic of 
slow, stable, accelerating flight and is probably an effort to get as 
much forward thrust and lift as possible from the downstroke. The 
initiation of the upstroke begins with flexion of the strongly ad- 
ducted forearm, which raises the vertically oriented distal segment 
of the wing. Abduction and supination of the brachium begin rel- 
atively later than in the initial few wingbeats, perhaps to delay the 
flick phase until the wing is slightly above the level of the body. 
Early initiation of the flick phase from a ventral position would 
necessitate the abduction of the plagiopatagium in a relatively hor- 
izontal position over a fairly wide arc, and thus would require 
considerable energy. When the flick phase is delayed until the wing 
is above the body, the plagiopatagium is raised to the level of the 
body in an anteriorly oriented, stretched, low drag configuration 
(Fig. 22K-0). During the flick phase, the lateral plagiopatagium 
produces thrust along with the chiropatagium (Fig. 22P-S). As 
flight speed increases, the flick probably plays a lesser role in thrust 
generation. 

Alighting Maneuvers on Horizontal Surfaces 

As Desmodus is so highly terrestrially oriented in feeding behav- 
ior, the transition between flight and terrestrial locomotion on a 
horizontal surface is an important aspect of its locomotor behavior. 
Again, the maneuvers in this phase of locomotion are quite dif- 
ferent depending upon differences in the flight prior to alighting, 
the contour of the surface, and, no doubt, individual differences. 
Tracings from a high-speed motion picture film of a bat alighting 
from slow, almost hovering flight (about 0.2 m per second), show 
that as the wings are in position for a downstroke, there is a strong 
anterior movement of the forearms by an anterior swing of the 
brachii and flexion of the elbows (Fig. 23A-B). The forearms. 



50 Spec. Publ. Amer. Soc. Mamm. 6 





\f ^^ ^"^ "^^ ^% -"^ 

O H . ^ - \ . " . 

Fig. 23. Drawings at 10 millisecond intervals of Desmodus alighting on a hori- 
zontal surface. 



oriented parallel to the long axis of the body, which is inclined 
anteriorly, are lowered by adduction of the brachii to the level of 
the body (Fig. 23B-D), and the digits are folded toward the con- 
figuration seen in terrestrial locomotion. Strong flexion occurs at 
the joints between phalanges two, three, and four of digit III, and 
between phalanges one and two of digits IV and V. As the brachii 
are adducted below the middle of the body, pronounced extension 
of the elbows begins (Fig. 23D-E). Adduction and an anterior 
swing of the brachii orient the forelimbs almost vertically beneath 
the shoulders. Prior to contact with the substrate, the thumbs are 
nearly in line with the long axis of the forearms (Fig. 23E). As the 
thumbs contact the substrate, they bend upward at the metacar- 
pophalangeal joints to begin absorption of the impact. A posterior 
swing and abduction of the brachii shift the center of gravity an- 
teriorly over the forelimbs and, in combination with flexion of the 
elbows, begin to break the fall (Fig. 23F-I). Dorsolateral bending 
of the first metacarpals lowers the carpi to the substrate during 
these movements and also probably helps break the fall. The body 
remains inclined anteriorly below horizontal, but the hind limbs 
are flexed at the knees and adducted posterolaterally to accom- 
modate the ventral pull of the plagiopatagii. As the brachii are 
abducted to the level of midbody, the inclination of the body is 
reduced, thus dropping the hind limbs toward the substrate (Fig. 
23H-L). The folding of digits of the forelimbs is complete before 



Altenbach — Vampire Locomotor Morphology 51 

the hind limbs contact the substrate (Fig. 23L). Nearly all of the 
shock of the landing is absorbed by the pectoral limbs, and the 
hind limbs appear to absorb little of the energy. 

Many parts of the fall-breaking maneuver are similar to the 
movements seen in a jump, although the direction of movement 
is reversed. No electromyographic data are available, but no doubt 
the muscles that power the jump supply force to break a fall in a 
sequential series of contractions. The pelvic limbs play an even 
lesser role in alighting on a horizontal surface than during a jump. 

When released in confined and unfamiliar surroundings, Des- 
modus often lands on the floor with a solid "plop," indicative of 
little or no breaking of the fall. However, when accustomed to the 
surroundings, as in a large flight cage or in a roost, the alighting 
is delicate and almost noiseless. I assume that, when alighting on 
a horizontal surface from flight, the breaking maneuver of the 
pectoral limbs is used consistently. This behavior is of obvious ad- 
vantage to avoid internal injuries from a hard fall, and perhaps to 
lessen the noise of alighting when intending to feed on a host 
animal from the ground or to lessen the impact when alighting 
directly on the animal. Because my observations and those of oth- 
ers indicate that Desmodus often flies close to the ground (Wimsatt, 
1959), a simple stalling or braking maneuver could cut air speed 
and allow a short drop to the ground that would not necessitate 
strong breaking of a fall. 

Alighting Maneuvers on Vertical Surfaces 

When alighting on a vertical surface from forward flight, Des- 
modus characteristically executes a steep bank during the flick phase 
of the upstroke and brakes with a shallow downstroke. As the bat 
slows, its digits are rapidly flexed toward the forearm and the 
phalanges of digits III, IV, and V are flexed ventrally. The fore- 
limbs and hind limbs appear to contact the surface simultaneously 
in a spread position, as described by Eisentraut (1936) for Myotis 
myotis. In Desmodus, the hind limbs are flexed at the knee and 
oriented posterolaterally. The forelimbs are only slighdy flexed at 
the elbow, and the thumbs are directed laterally. Immediately 
upon alighdng, the bat turns head down by alternate flexion of 
the hind limbs, and hangs in the characteristic posture with the 
hind legs flexed at the knee and the forelimbs slighdy flexed and 



52 Spec. Publ. Amer. Soc. Mamm. 6 

oriented laterally. The thumbs are directed dorsolaterally, with the 
weight distributed between the daws and the two pads, which press 
into depressions in the surface. The head is strongly upturned, 
and the body is inclined outward between 10 and 20 degrees from 
the surface. From this position the bat can climb or jump into 
forward flight as described earlier. The turn after alighting is so 
rapid that the bat appears to alight upside down after a sharp 
banking turn toward the surface. 

POSTCRANIAL OSTEOLOGY 



Positional Terminology 

FOLLOWING the practice of Vaughan (1959, 1966, 1970^, 1970c, 
1970rf), I have used the same positional terms for the bat body 
as employed for other vertebrates. The arm and manus (wing) are 
described as though fully extended in the middle of the downstroke 
(Fig. 24). The pollical side of the manus is anterior, digit V is 
directed posteriorly, digit IV is directed posterolaterally, and digits 
III and II are directed laterally to the level of the first interphal- 
angeal joint of digit III. The terminal phalanges of digit III are 
oriented posterolaterad. The palmar surface of the hand and wing 
is considered ventral and the opposite side is considered dorsal. 
Following Norberg (19706), the upper side of the bones of the arm 
is considered as dorsal, the lower side as ventral. Thus the ulnar 
side of the radius is posterior, the opposite side anterior. When 
strongly flexed, the forearm opposes the anterior surface of the 
humerus. 

The hind limbs of a bat are oriented differently from those of 
other mammals, and positional terms for them are confusing. This 
problem is particularly severe in Desmodus, because the hind limbs 
are extremely mobile and can be oriented in more positions than 
those of other bats. For general descriptive purposes, the limb is 
considered as in flight during the first part of the downstroke (Fig. 
19A) when it is oriented similarly to the hind limb of Macrotus 
(Vaughan, 1959). The plagiopatagial side of the limb is considered 
lateral, the opposite side is medial; thus the tibia is lateral, and the 
fibula is medial. The hind foot is oriented with the plantar side 



Altenbach — Vampire Locomotor Morphology 53 




chiropatagium 



Fig. 24. Ventral view of Desmodus with parts of the flight membranes and po- 
sitional terms relative to the arm, hand, and pelvic limb: I-V are metacarpals of 
corresponding digits and 1-4 are phalangeal elements; superscript "c" indicates the 
phalanx is cartilaginous. The right wing is folded as in terrestrial locomotion and 
the left wing is extended as in mid-downstroke of forward flight. 



ventral and the opposite side dorsal. Movements in the plane of 
the wing membranes are termed either tibial or fibular. Digit V is 
located on the medial side of the foot and digit I on the lateral 
side. 

Vertebral Column 

Desmodus has seven cervical, 12 thoracic, six lumbar, five sacral, 
and no caudal vertebrae. Only the most significant features of the 
vertebrae are described below. 

Cervical vertebrae. — The atlas and axis allow extreme lateral and 
vertical mobility of the skull, which is advantageous for making 
incisions in a host animal prior to feeding. The remainder of the 
cervical vertebrae are relatively short and broad and have well- 
developed transverse processes. These processes have a broad, 
flange-like projection ventrally and a thin posterodorsal projection 
that serves for the origin of the four slips of the M. levator scapulae 
on the last four vertebrae. 

Thoracic vertebrae. — Anteriorly the vertebrae are relatively short 



54 Spec. Publ. Amer. Soc. Mamm. 6 



lateral process 




articular facet for clavicle 



1st costal cart. 



manubrium 



body 



xiphoid process 




ventral process 



posterior process 



Fig. 25. Sternum and first costal cartilages of Desmodus. A, ventral aspect; B, 
lateral aspect. 



and wide, and become increasingly longer and narrower poste- 
riorly. The articulations between these vertebrae are similar to 
those of Macrotus as described by Vaughan (1959), but are more 
rigid, and the vertebral elements are closer together, providing a 
sturdy chain of bone. 

A solid, tubercle-like, spinous process projects 1 mm dorsally 
from the mid-dorsal portion of the vertebral arch of the first tho- 
racic vertebra. Bordered laterally by ridges that give rise to thin 
projections extending posteriorly beyond the border of the ver- 
tebra, it serves for the point of origin of the thickest portion of the 
trapezius muscles. The spinous processes of the next two vertebrae 
are represented by slight mid-dorsal elevations bounded laterally 
by prominent, posteriorly projecting ridges similar to those de- 
scribed on the first thoracic vertebra. On more posterior vertebrae, 
these ridges converge toward the midline and at the fifth thoracic 
vertebra, fuse medially to form a mid-dorsal ridge approximately 
0.5 mm wide. On the sixth and successive vertebrae these ridges 
widen posteriorly to form a triangular dorsal prominence. The 
apex of the prominence on the last thoracic vertebra is directed 
anteriorly and is 1.2 mm in width at the posterior margin of the 
vertebra. 

Lumbar vertebrae. — The mid-dorsal spinous processes are more 



Altenbach — Vampire Locomotor Morphology 55 

pronounced on the lumbar vertebrae. They become arrowhead- 
shaped, and the anterior point of one vertebra projects into a pos- 
terior indentation on the one before it. The spinous processes on 
the third, fourth, and fifth lumbar vertebrae are extremely high, 
and those of the fourth and fifth are low anteriorly and project 
strongly upward and backward. The centrum of the last lumbar 
vertebra is fused with the centrum of the first sacral vertebra and 
its transverse processes articulate laterally with the medial borders 
of the ilia. 

Sacral vertebrae. — These are completely fused to each other and 
laterally to the medial aspect of the ilia. The fused vertebrae taper 
posteriorly into a laterally compressed rod of bone that arches 
posterodorsally for almost the length of the pelvic girdle. The pos- 
teroventral margins of the fused vertebrae are fused to the ischia 
immediately dorsal to the ischial tuberosities. 

Sternum 

In Desmodus, the sternum is composed of three distinct parts — 
manubrium, body, and xiphoid process — joined by thin cartilagi- 
nous discs. The manubrium has a laterally compressed and slightly 
anteriorly directed ventral process (Fig. 25A-B). Lateral processes 
project about 15 degrees dorsally and swing slightly anteriorly to 
enlarged distal ends, which have an anterolaterally and slightly 
dorsally oriented articular surface for the clavicle and a laterally 
directed articular surface for the first costal cartilage (Fig. 25A-B). 
A posterior process, approximately 2.5 mm long and triangular in 
cross-section, has a ventral apex that forms a thin ridge continuous 
anteriorly with the posterior edge of the ventral process. The ar- 
ticular facets of the costal cartilages of the second pair of ribs are 
located on the posterolateral surfaces of the posterior process. 

The elongate body of the sternum is about 8 mm in length. It 
is roughly triangular in cross-section, slightly rounded dorsally, 
and, unlike many phyllostomatid bats, has no enlarged midventral 
keel. Articular facets for the costal cartilages of ribs three through 
six are arranged along the lateral borders at progressively shorter 
intervals (Fig. 25A-B). 

The xiphoid process is slightly less than half the length of the 
body and is almost square in cross section in its anterior region. 



56 Spec. Publ. Amer. Soc. Mamm. 6 

The costal cartilages of the seventh pair of ribs articulate on the 
anterolateral aspects of the xiphoid process. Posteriorly the xi- 
phoid process becomes dorsoventrally flattened and terminates in 
an expanded flange. 

Ribs 

The rib cage is about 1.4 times as broad and 1.1 times as deep 
as it is long. In one specimen, it was about 5 mm deep and 13.5 
mm wide at its anterior end, and was expanded posteriorly to a 
depth of about 18 mm and breadth of 26 mm. 

The first rib is strongly thickened anteroposteriorly as described 
by Vaughan (1959, 1970^) for other species of bats. A stout tu- 
bercle is found on the dorsal aspect immediately distal to the tu- 
berculum. The rib arches gently dorsad and terminates in an ex- 
panded tip, which articulates with the thick, first costal cartilage. 
The costal cartilage is parallelogram-shaped and articulates on its 
dorsal surface with the first rib and on its medial surface with the 
lateral process on the manubrium. Inasmuch as the remaining cos- 
tal cartilages of the sternal ribs are thin, the first costal cartilages 
provide much of the support of the sternum and reinforce it 
against the powerful dorsolateral pull of the sternal M. pectoralis. 
The second and third ribs are anteroposteriorly flattened, but cau- 
dally the ribs become dorsoventrally and laterally flattened. Rib 
seven is the last sternal rib, and the costal cartilage of rib eight 
connects with its costal cartilage. The cartilage of rib nine attaches 
to the costal cartilage of rib eight, but the cartilage of rib 10 con- 
nects directly with rib nine and the cartilage of rib 1 1 connects to 
rib 10. The twelfth rib is normally less than a millimeter long and 
has poorly defined distal connection. 

Pectoral Girdle and Limb 

Scapula (Fig. 26). — Viewed dorsally, the scapula is roughly elip- 
tical posteriorly, truncate anteriorly, and about 41 per cent as wide 
as it is long. The glenoid fossa is directed slighdy craniolaterally. 
The ardcular surface is anteroposteriorly elongated and is twice as 
high posteriorly as anteriorly. The posterior half of the fossa is 
deeply concave and strongly reinforced posteriorly by the expand- 



Altenbach — Vampire Locomotor Morphology 57 



coracoid process 




coracoid proc. 



scapular flange 

onnective tissue b 
supraspinous fossa 

spine 



anteromedial 
facet 



ntermediate 
facet 



posterolatera 
facet 




glenoid fossa 
lateral border 
supraglenoid tuberosity 
coracoid process 




acromion process 



scapular flange 



Fig. 26. Scapula and proximal portion of humerus of Desmodus: Ventral view 
of right humerus (A) and scapula (B); dorsal view of right humerus (D) and scapula 
(C); anterior view of right scapula (E). 



ed lateral scapular border. Paired infraglenoid tuberosities are sit- 
uated immediately posterior to the fossa and serve as points of 
origin for slips of the long head of the M. triceps brachii. The thick 
lateral scapular border slopes gently posteromedially and becomes 
progressively thinner toward the rounded posterior margin. The 
medial border, which is not as thick as the lateral border, is nearly 
parallel with the long axis of the body. Anteriorly, the medial bor- 
der is thickened dorsoventrally and curves laterally to form the 
scapular flange. Lateral to the flange, the anterior scapular border 
is concave for about 2 mm, and then becomes thickened and di- 
rected anteriorly to form the projection that is the base of the 
coracoid process. Laterally, the thickened anterior process bears 
a small supraglenoid tuberosity that lies immediately anterior to 
the glenoid fossa. 

The anteroposteriorly flattened coracoid process extends ven- 
trally from the thickened anterior projection of the scapula, medial 
to the supraglenoid tuberosity, and then curves laterally and slight- 
ly posteriorly. The tip of the coracoid process is expanded and lies 
below and slightly lateral to the middle of the glenoid fossa. 

The dorsal surface of the scapula is transected by the scapular 



58 Spec. Publ. Amer. Soc. Mamm. 6 




Fig. 27. Diagrammatic frontal view of the pectoral girdle of Desmodus: A, right 
clavicle and scapula tipped ventrally and right humerus fully adducted as might 
occur at the end of a jump; B, position of left clavicle, scapula and humerus at the 
start of a jump or downstroke. The lateral scapular border is tipped upward and 
the humerus is locked dorsally with the scapular border. 



spine, which runs from the medial border anterolaterally toward 
the posterior half of the glenoid fossa. Quite low medially, the 
spine becomes progressively higher laterally and, about 4 mm from 
the glenoid fossa, curves sharply cranially and dorsally to the 
anteroposteriorly flattened acromion process. The distal 3 mm of 
the acromion process is thickened and strongly anteroventrally 
curved so that it lies medial to, and above, the glenoid fossa. The 
lateral border of the acromion process arises about a millimeter 
medial to the highest point of the glenoid fossa. A strong band of 
connective tissue runs from the dorsolateral aspect of the flange 
to the medial surface of the expanded tip of the acromion process, 
and helps brace the latter against the pull of the abductors and 
supinators of the humerus. The anteroposterior flattening of the 
process and the increased height of the scapular spine also aid in 
resisting these forces. 

In Desmodus, the supraspinous fossa is smaller relative to the 



Altenbach — Vampire Locomotor Morphology 59 

infraspinous fossa than in some of the closely related phyllostom- 
atids. A thickened ridge extending from the base of the acromion 
process to the anteromedial edge of the posterior border separates 
the large anteromedial facet from the small and nearly vertically 
oriented intermediate facet. Another thickening separates the in- 
termediate facet from the nearly horizontally-oriented postero- 
lateral facet. The vertical orientation of the intermediate facet pro- 
vides a solid surface for muscular attachment and reduces the 
relative width of the entire facet. This suggests that the muscle 
mass that originates there, the M. infraspinatus, is suited for pow- 
erful contraction in a limited direction. Posteriorly the scapula ter- 
minates in a cartilaginous extension typical of many other bats. 

Clavicle (Fig. 27). — The proximal articular surface is greatly en- 
larged, rather ovoid, and elongate laterally. Within 2 mm of the 
articular surface, its diameter constricts to about a millimeter. At 
this point the clavicle is nearly circular in cross-section, but becomes 
laterally compressed distally. 

In specimens preserved with the wing folded in the typical pos- 
ture seen in hanging, the long axes of the proximal half of the 
clavicles are oriented about 20 degrees anterolateral and about 30 
degrees anterodorsal to the long axis of the body. From their prox- 
imal articulations, the clavicles curve gently posterodorsally and, 
over the proximal 80 per cent of their length, become increasingly 
deeper (anteroposteriorly) in cross-section. The distal 20 per cent 
of each clavicle is curved sharply posteriorly, and the slightly ex- 
panded distal tip is displaced about 3 mm posterior to the long 
axis of the proximal shaft. 

The ventrolateral aspect of the distal 1.5 mm of the clavicle is 
bound by tough connective tissue to the ventromedial surface of 
the anterior tip of the scapula. The articular surface is elongate 
and nearly horizontal, a configuration that permits the scapula to 
tilt about its long axis relative to the clavicle. Angular displacement 
of the long axis of the scapula is hmited to only a few degrees by 
the articulation. However, when the lateral scapular border is 
rocked strongly ventrally, the articulation allows the long axis of 
the scapula to be inclined upward posteriorly between 10 and 15 
degrees. This suggests that the anterior end of the scapula is com- 
monly tipped ventrally when the lateral scapular border is tipped 
ventrally, as in a jumping maneuver or in certain terrestrial feeding 
postures. This helps explain the apparent depression of the shoul- 



60 Spec. Publ. Amer. Soc. Mamm. 6 

der joint during these movements. The curvature of the posterior 
surface of the clavicle, adjacent to its distal tip, perfectly matches 
the curvature of the coracoid process, and allows the coracoid pro- 
cess to swing behind the clavicle (Fig. 27 A). The scapula can be 
rotated about its long axis to position the coracoid process directly 
behind the clavicle. When the clavicle is inclined a normal 40 de- 
grees above horizontal (viewed frontally), this rotation of the scap- 
ula orients the short scapular axis vertically, thus directing the 
glenoid fossa ventrally. This is the most striking feature of the 
pectoral girdle osteology of Desmodus and is partly responsible for 
the high quadrupedal stance and remarkable jumping ability of 
the species, as it allows the humerus to be directed completely 
ventrally. 

At the clavo-scapular articulation, the surfaces of both the clav- 
icle and scapula are bordered dorsally by nearly vertical bony sur- 
faces that limit upward rotation of the lateral scapular border. 
When the short axis of the scapula is within a few degrees of being 
parallel to the long frontal axis of the clavicle, following upward 
rotation of the lateral scapular border (Fig. 27B), the supra-arti- 
cular surfaces meet and stop further rotation. Rotational forces 
applied to the scapula are thus transferred to the clavicle. A strong 
connective tissue band runs from the middle anterior surface of 
the clavicle to the middle of the coracoid process and aids in stop- 
ping the upward lateral rotation of the scapula. The articulation 
of clavicle and scapula allows rotation of the short axis of the scap- 
ula through an arc of fully 120 degrees. 

Humerus (Figs. 26-28). — This bone is relatively stocky in Desmo- 
dus; the greatest diameter of the middle diaphysis is about 5.4 per 
cent of the length. The head is directed posterior to the proximal 
end of the shaft. Anterior to the head is a deep depression (Fig. 
28E) into which the supraglenoid tuberosity fits when the humerus 
is extended anteriorly. The greater tuberosity extends postero- 
dorsally and medially from the medial end of the shaft. The ridge 
of bone that runs between the tuberosity and the dorsal aspect of 
the head articulates with the dorsal border of the glenoid fossa to 
stop abduction of the humerus (Fig. 27B). Anteriorly, the greater 
tuberosity gives way to a ridge that projects anteroventrally to meet 
the medial end of the pectoral ridge. The lesser tuberosity projects 
posteroventrally and medially from the medial end of the shaft, 
and is continuous laterally with a low midventral ridge that extends 



Altenbach — Vampire Locomotor Morphology 61 



pectoral ridge 




dorsal epicondyle 
spinous process 




greater tuberosity 
pectoral ridge 



dorsal epicondyle 




capitulum 
trochlea 
spinous process 




head 




cap. 



troch. 
spin, proc 



greater tuberosity 
pectoral ridge 




cap. — 
troch. 



spin. proc. 



lesser tuberosity 




Fig. 28. Humerus of Desmodus: A, dorsal view; B, ventral view; C, anterior view 
of proximal end; D, posterior view of proximal end; E, medial view of proximal 
end; F, anterior view of distal end; G, posterior view of distal end; H, lateral view 
of distal end. 



62 Spec. Publ. Amer. Soc. Mamm. 6 

for several millimeters along the shaft and ends in a small tubercle 
about 6.5 mm distal to the tip. A ridge runs anterodorsally from 
the lesser tuberosity to the ventromedial base of the pectoral ridge. 
The importance of the rotative forces applied by the muscles that 
insert on the greater and lesser tuberosities is reflected by the 
ridges that run from their bases anteriorly to the medial end of 
the pectoral ridge. 

The pectoral ridge projects anteriorly about a millimeter from 
the middle of the proximal end of the shaft, beginning adjacent 
to the head, and continues distally for about 8 or 9 mm. The ridge 
is divided in its middle part into two ridges, one below the other, 
but it becomes quite thin about 2.5 mm distal to that point and is 
thin for the remainder of its length. 

For the first one-fourth of its length, the shaft is quite straight 
and roughly circular in cross section except for the pectoral ridge. 
The distal three-fourths of the shaft is strongly bowed posteriorly 
and compressed anteroposteriorly. The anterior aspect of the dis- 
tal half is slightly concave. These structural features apparently 
strengthen the distal shaft against the torque and strong upward 
forces encountered in the wingbeat cycle and terrestrial locomo- 
tion. The bowing of the distal three-fourths accomodates the 
prominent forearm musculature when the forearm is strongly 
flexed toward the humerus during terrestrial locomotion. 

The locking mechanism between the humerus and scapula of 
other bats described by Vaughan (1959) and others is quite evident 
in Desmodus and limits adduction and abduction to about 30 de- 
grees above and below the short axis of the scapula (Fig. 27). How- 
ever, the depression anterior to the head of the humerus is suffi- 
ciently deep, and the supraglenoid tuberosity is sufficiently small 
and anteriorly positioned, that the humerus can be extended to 
within 30 degrees of the long axis of the lateral scapular border 
before being stopped by this locking mechanism. Anterior exten- 
sion of the humerus is necessary for alighting on a horizontal sur- 
face (Fig. 23), a backward jump (Fig. 12), and climbing on a vertical 
surface (Fig. 6). 



Fig. 29. Right radius and ulna oi Desmodus. A, dorsal view; B, ventral view; C, 
anteromedial view of proximal end; D, ventral view of proximal end; E, dorsal view of 
proximal end. 



Altenbach — Vampire Locomotor Morphology 63 
sesamoid for triceps tendon 





radius 



ulna 



radius 




flexor fossa for biceps tendon 



ulna 



ulna 



radius 




64 Spec. Publ. Amer. Soc. Mamm. 6 

The distal articular surfaces formed by the capitulum and the 
trochlea are displaced anteriorly and slightly dorsally to the axis 
of the shaft (Fig. 28F-H). The groove separating the two inclined 
surfaces of the capitulum is rather shallowly concave, whereas the 
groove separating the capitulum from the ventral trochlea is deep- 
er and rather V-shaped in section. The prominent ventral flange 
of the trochlea continues to the posterior side of the epiphysis, 
where the groove above it is broadened and bordered above by 
the ridgelike, posterior continuation of the dorsal side of the ca- 
pitulum. The ulna and the elongate sesamoid of the M. triceps 
brachii tendon (Fig. 29A-B) run into this groove as the forearm is 
extended. The epicondyle above the capitulum is indented (Fig. 
28 A), and the M. supinator arises from the center of this indenta- 
tion. Proximally, a small ridge runs posteromedially to the shaft 
and serves for the point of origin of the M. extensor carpi radialis 
longus and M. extensor carpi radialis brevis. Ventrally, the epicondyle 
(medial epicondyle) extends slightly more than 2 mm to form a 
spinous process (Fig. 28B, 28F-G). The tip of this process is located 
directly below the center of rotation of the radius; thus, flexion 
and extension of the radius do not affect the length of the muscles 
that originate on the spinous process. 

Radius and ulna (Fig. 29). — The radius is about 1.6 times the 
length of the humerus and over its proximal half curves strongly 
posteriorly and ventrally (Fig. 29A-B). The proximal articular sur- 
face is directed anteromedially and has a central concavity that is 
bordered dorsally and ventrally by low ridges and adjacent flat- 
tened areas (Fig. 29B-D). The rounded ventral part of the capit- 
ulum fits into the central concavity, and the inclined dorsal portion 
of the capitulum and the ventral trochlea articulate with the nar- 
row flattened surfaces above and below the concavity. The con- 
cavity is in line with the axis of the shaft and is bordered ventrally 
by a flange that makes up the ventral articular surface. A promi- 
nent ridge of bone extends from the anterior border of this sur- 
face, at the level of the bottom of the concavity, laterally for about 
5 mm (Fig. 29B, 29D). Posterior to this ridge is a flattened, pos- 
terodorsally inclined surface that ends in a deep groove (the flexor 
fossa) on the posterior face of the radius. The tendons of the M. 
biceps brachii and M. brachialis run ventrally over the ridge imme- 
diately distal to the ventral flange and insert into the flexor fossa. 
Thus, contraction of these muscles exerts both a flexive force to 



Altenbach — Vampire Locomotor Morphology 65 

the forearm and a powerful supinating force to the entire arm, as 
the articulation of the humerus and radius severely limits any 
movement except flexion and extension. 

The thickened proximal end of the ulna is positioned posterior 
to the ventral half of the proximal articular surface of the radius 
and projects 1.5 mm beyond its proximal tip (Fig. 29A, 29D). A 
vertical groove on the anterior surface of the ulna articulates with 
a ridge on the posterior surface of the radius about 1.5 mm distal 
to its end. A groove distal to the ridge on the radius accepts a ridge 
on the ulna. This tongue-in-groove mechanism stabilizes the ulna 
against the medial pull of the M. triceps brachii. Distal to the thick- 
ened proximal articular area, the shaft of the ulna is thin and 
concave anteriorly. The ulna is fused distally to the posterodorsal 
surface of the radius at about the middle of the radial shaft. The 
rigid fusion distally and strong articulation proximally suggest that 
the ulna is important in bracing the radius against forces directed 
toward its long axis during terrestrial locomotion or jumping. It 
also affords a rigid structure for muscle attachment. Distal to the 
fusion of the ulna and radius, a thin ridge runs along the postero- 
dorsal surface of the radius to within 5 mm of its distal end. The 
ridge is the same thickness and width as the ulna before its fusion 
to the radius. Although no embryologic evidence is available, this 
ridge may represent the distal end of the fused ulna. The concave 
underside of this ridge serves for muscle attachment. Distal to the 
fusion of the ulna with the radius, the radius is diamond-shaped 
in cross section. The broad, anterodorsal surface of the distal 2 or 
3 mm is divided by bony ridges into grooves for the tendons of 
several of the forearm muscles (Figs. 30-31). Anteroventrally, two 
ridges of bone make a deep channel for the M. abductor pollicis 
longus. The large, posterodorsal ridge bordering this channel is the 
anteroventral edge of a pair of channels divided by a small median 
ridge. The lower channel accommodates the M. extensor carpi ra- 
dialis longus and the upper accommodates the M. extensor carpi ra- 
dialis brevis. Posterodorsally, a broad flat surface separates these 
channels to form a prominent posteriorly-projecting flange at the 
distal tip of the radius. This flange is the dorsal edge of a channel 
bordered ventrally by a median projection of the cuneiform. The 
tendons of the M. extensor pollicis brevis, M. extensor digitorum com- 
munis to digits III and IV, and the M. extensor indicis run through 
this channel. On the posterior surface of the radius medial to this 



66 Spec. Publ. Amer. Soc. Mamm. 6 




Fig. 30. Dorsal view of the right carpus and first digit of Desmodus. 



channel is a large backward-projecting flange of bone that supports 
the tendons ventrally and functions as a posterior extension of the 
ventral aspect of the channel described above. This flange on the 
radius also forms a shelf for the tendon of the M. extensor digiti 
quinti proprius to digit V and the tendon of the M. extensor carpi 
ulnaris. The tendons are bound to this shelf of bone by a tough 
ligamentous band, which runs from the posterior tip of the shelf 
to the posterior tip of the cuneiform. The exceptional investrrient 
of the distal portion of the radius with grooves and ridges of bone 
to confine tendons reflects the great forces placed upon the ten- 
dons, and thus elements in the hand, during terrestrial locomotion, 
jumping, and initial flight. 

The distal articular surface of the radius is deeply concave and 
directed posterolaterally from the long axis of the shaft. The pos- 
teroventral surface of the border of the articular surface bears a 
prominent lateral projection, which interlocks with the deep notch 
in the posterior aspect of the lunar. The edge of the articular 
surface posterodorsal to the projection forms a ridge that serves 
to hold the lunar in position. Anteroventrally, the projection con- 
tinues as a ridge of bone that confines the lunar ventrally and helps 
limit it to movement on only one plane. 

Manus (Figs. 30-31). — The lunar is the largest of the eight car- 
pals and is elongate parallel to the long axis of the distal articular 
surface of the radius. The body of the lunar is offset posteroven- 
trally to the long axis of the shaft and bound to the shaft by heavy 
ligaments on the posterodorsal surface. On the posteromedial as- 
pect of the lunar is a deep groove that interlocks medially with the 



Altenbach — Vampire Locomotor Morphology 67 



scaphoid 




Fig. 31. Ventral view of the right carpus and first digit of Desmodus. 



distal projection on the posteroventral side of the articular surface 
of the radius and limits flexion of the lunar. The cuneiform is 
tightly bound to the radius posterodorsally to the lunar and bears 
a posteromedial projection that forms the ventral half of the deep 
channel described above. The posterior tip of this projection 
curves strongly dorsally, making the channel almost tubular (Fig. 
30). 

A cylindrical anteroventral projection of the lunar bears a 
smooth surface anteriorly on which the small ovoid scaphoid rests. 
A deep circular groove separates the projection posterodorsally 
from an expanded circular ridge perpendicular to the long axis of 
the lunar. This groove accommodates a prominent anteromedial 
projection from the flattened trapezium and stabilizes it as the 
carpus is flexed and extended. The anterodorsal surface of the 
lunar posterior to the lateral ridge is saddle-shaped and accom- 
modates an anteromedial projection of the small trapezoid that 
projects from beneath the overlying trapezium. The lateral artic- 
ular surfaces of the lunar limit the movements of the trapezium, 
trapezoid, magnum, and cuneiform to a single plane, that of lateral 
extension and medial flexion. 

Distally, the cuneiform projects anteroventrally parallel to the 
long axis of the lunar and forms a broad articular surface that 
contacts the posteromedial aspect of the cuneiform. The trapezoid, 
which rides against the posterodorsal surface of the ridge on the 
lunar, serves as a spacer between the trapezium and the adjacent 



68 Spec. Publ. Amer. Soc. Mamm. 6 

magnum. The magnum bears a prominent posteroventrally-di- 
rected spine beneath the rounded articular surface, which slides 
against the deep lateral depression of the lunar. As the magnum 
is flexed, this spine locks against the posterior surface of the lunar. 
Distal to its articulation with the lunar and the cuneiform, the 
unciform is expanded and bears on its posterior surface a deep 
groove bordered above and below by slightly convex articular sur- 
faces. The long axis of the groove is inclined medially, slightly 
above the long axis of the radius, and accommodates the fingerlike 
projection on the proximal end of metacarpal IV. The surfaces 
above and below the groove accommodate proximal portions of 
metacarpals IV and V, respectively. Distally, the arrangement of 
the trapezium, trapezoid, magnum, and cuneiform produces deep 
notches on the posterolateral surface of the carpus, which receive 
the proximal processes of metacarpals II and III. 

The long axis of the rodlike pisiform is oriented obliquely across 
the posterior surface of the carpus from the medial projection of 
the trapezium adjacent to its articulation with the lunar postero- 
dorsally to the posteromedial tip of the cuneiform. Heavy liga- 
ments bind the pisiform to the posteromedial tip of the cuneiform, 
the posteromedial surface of the magnum, and the medial tip of 
the trapezium. A large tubercle projects from the posterior surface 
of the pisiform immediately ventrad to its dorsal tip, which is flat- 
tened into a smooth articular surface. This dorsal articular surface 
meets the flattened and slightly ovoid ventral surface of the prox- 
imal tip of metacarpal V. The articular facet on the metacarpal is 
oriented ventral and perpendicular to the slightly concave proxi- 
mal articular facet that contacts the cuneiform. 

Digit I (Figs. 30-31). — The proximal articular surface of the first 
metacarpal slopes anterolaterally from its ventral ligamentous at- 
tachment to the broad, flattened, distal surface of the trapezium, 
which slopes anteromedially. The articulation allows considerable 
freedom of movement, and the first metacarpal can be adducted 
or abducted through an angle of about 130 degrees. The first 
metacarpal is the thickest of the metacarpals and about 7 mm long, 
longer than the entire pollux of most other microchiropteran bats. 
Its thickness reflects the forces it bears in terrestrial locomotion 
and jumping. The distal articular surface is rounded, allowing 
movement of the first phalanx in almost any plane. The proximal 
articular surface of the first phalanx is deeply concave to accom- 



Altenbach — Vampire Locomotor Morphology 69 

modate the rounded articular surface of the metacarpal, and the 
hingelike distal articular surface limits movement of the short sec- 
ond phalanx (which bears a recurved claw), to flexion and exten- 
sion. 

Digit II (Figs. 30-31). — The proximal end of the second meta- 
carpal is vertically expanded and compressed anteroposteriorly 
into a rounded flange, which articulates in the groove between the 
trapezium and the magnum. The anterior tip of the flange rests 
against the posterolateral tip of the trapezoid. Distally, there is a 
ventral tubercle that articulates with the proximal part of meta- 
carpal III. Two milhmeters distal to this tubercle there is a small 
posterodorsal saddle, bordered distally by a tubercle, into which 
articulates the large, anterodorsal tubercle of metacarpal III. This 
is the spacer described by Vaughan and Bateman (1970) that main- 
tains the spread of the second and third metacarpals in bats with 
a large dactylopatagium minus. Because Desmodus does not have 
a large dactylopatagium minus, this tubercle is quite small. 

The second metacarpal is approximately 81 per cent of the 
length of metacarpals III through V. Its distal articular surface 
and the proximal articular surface of the first phalanx are ex- 
panded, flattened, and nearly perpendicular to the long axis of the 
digit. Firm ligamentous binding of the joint limits movement and 
stabilizes the leading edge of the chiropatagium. The second pha- 
lanx is cartilaginous and serves only as a connection between the 
second and third digits to stabilize the leading edge of the chiro- 
patagium. 

Digit III (Figs. 30-31). — Medially the metacarpal is enlarged and 
flattened into a vertically-oriented flange similar to, but larger 
than, the flange of metacarpal II. The flange fits into a shallow 
curved depression on the posterior surface of the magnum and is 
bordered posteriorly by the concave, flattened anterolateral por- 
tion of the distal part of the cuneiform. There is a prominent 
depression on its posterior surface that accommodates an ante- 
riorly-directed process on the anteroventral aspect of the proximal 
tip of metacarpal IV. The distal articular surface of metacarpal III 
is expanded to one and a half times the diameter of the distal shaft 
and, along with the proximal articular surface of the basal phalanx, 
is perpendicular to the long axis of the shaft. The long axis of the 
shaft of the basal phalanx is offset dorsally and in line with the 
dorsal aspect of the shaft of the metacarpal. The metacarpopha- 



70 Spec. Publ. Amer. Soc. Mamm. 6 

langeal joint allows limited movement in any direction, but liga- 
mentous binding limits upward deflection. Much of the stability of 
this joint is provided by medially directed forces imparted by the 
tendons inserting on the first phalanx. Compression of the shaft 
forms a ventral notch proximal to the distal articular surface. The 
trochlealike articular surface bears a shallow vertical groove on its 
dorsal and distal surface. The proximal articular surface of the 
second phalanx is deeply concave and bears a dorsomedian process 
that curves strongly proximad to articulate dorsally with the groove 
of the distal surface of phalanx one. Lateral processes of phalanx 
two articulate medially with the lateral edges of the trochlea of the 
first phalanx and limit the movement of this joint to a vertical 
plane. The second phalanx can be deflected about 30 degrees 
above the long axis of the metacarpal and first phalanx, but this 
movement is then stopped by the dorsomedian process of the sec- 
ond phalanx. Ventral flexion through an arc of more than 90 
degrees is possible as the ventral aspect of the articular surface of 
phalanx two fits into the notch proximal to the distal tip of the 
first phalanx. The second interphalangeal joint is flattened and 
similar to the metacarpophalangeal joint. All but ventromedial 
flexion is restricted by a firm ligamentous binding. 

Digits IV and V (Figs. 30-31). — From the anterolateral aspect of 
the proximal articular surface of metacarpal IV, a spine projects 
anteriad to fit into the depression on metacarpal III. This serves 
as a center of rotation that allows upward deflection of the fourth 
metacarpal. However, if the hand is extended, a flange on the 
anterodorsal edge of metacarpal IV slides into the posteriorly- 
turned dorsal edge of the articular flange of metacarpal III and 
stops this movement. This effectively braces the fourth metacarpal 
against upward displacement from the forces of the airstream as 
the extended wing is adducted. A posteromedially directed fin- 
gerlike projection of the proximal articular surface of metacarpal 
IV articulates with the groove in the distal surface of the cunei- 
form. The depression dorsal to the projection fits over the convex 
surface above the groove on the cuneiform. This arrangement 
prevents any rotation of the shaft, which would reduce the effec- 
tiveness of the dorsal bracing previously described. 

The proximal surface of metacarpal V bears a central notch that 
fits against the fingerlike posteromedial projection of the fourth 
metacarpal. Dorsally, a projection of the fifth metacarpal fits into 



AUenbach — Vampire Locomotor Morphology 71 

a depression on the posteromedial and dorsal aspect of the fourth 
metacarpal and prevents upward deflecdon of the fifth metacarpal 
when the wing is extended and forced downward against the air- 
stream. 

The ventromedial surface bears a tubercle that projects antero- 
laterally and fits into a groove on the posteromedial and ventral 
part of metacarpal IV. Strong tendinous binding here further 
braces the fifth metacarpal against upward deflection by the air 
stream. Medial to the central notch, a flat articular surface curves 
posteriorly and articulates with the flattened distal surface of the 
cuneiform below the groove that accommodates the fingerlike pro- 
jection on metacarpal IV. The distal articular surfaces of the fourth 
and fifth metacarpals are similar to that of the third, but typically 
slope proximally on their ventral edge, allowing ventral flexion of 
the first phalanges through an arc of more than 90 degrees as the 
wing is folded. The proximal articular surfaces of the first pha- 
langes of digits III and IV are flattened and similar to that of the 
first phalanx of digit III. 

The first interphalangeal articulations of digits IV and V are 
similar to the first interphalangeal articulation of digit III. Digits 
IV and V have similar dorsomedial projections on the proximal 
articular surfaces of the second phalanges, which, unlike the less 
restrictive arrangement seen at the first interphalangeal joint of 
digit III, limit upward deflection of the second phalanges to a 
position parallel to the long axis of the basal phalanges. As the 
metacarpophalangeal joints allow considerable upward deflection, 
there is little need for additional deflection at the interphalangeal 
joints. However, ventral flexion through an arc of more than 100 
degrees is permitted to facilitate folding of the wing. Lateral move- 
ments of the distal phalanges of digits IV and V are limited by 
ligamentous binding, which holds the second phalanges by their 
lateral articular surfaces against the distal articular surface of the 
basal phalanges, and by proximolateral projections, which articu- 
late with the distolateral surfaces of the basal phalanges. 



FUNCTIONAL MYOLOGY OF THE 
PECTORAL GIRDLE AND LIMB 

IN the following descriptions I follow the system of muscle ter- 
minology used by Vaughan (1959) who, in turn, followed those 
of Hill (1937) and Rinker (1954). However, I have used the same 
positional terms as in the previous section on osteology. Thus, the 
body, arm, and hand are described as in forward flight with the 
wing fully extended in mid downstroke. 

Comments on Electromyographic Analysis 

Without implant of a tension transducer in series with the in- 
sertional tendon of a specific muscle, there is no way of determin- 
ing the exact amount of tension that a muscle exerts on its insertion 
and origin or the temporal distribution of that tension in normal 
movements. 

However, electromyography provides useful information about 
both parameters if the electromyographic record is accurately in- 
terpreted. Bigland and Lippold (1954) and Bergstrom (1959) have 
demonstrated that tension varies directly with the integrated po- 
tential changes and that spikes of an electromyogram can be used 
to estimate the relative tension generated by a given muscle. Bas- 
majian (1962) suggested that the number of spikes, the degree of 
their superimposition, and their relative height and type, are im- 
portant factors in analysis of muscular function through an elec- 
tromyogram. He stated: "Experience has shown that the easiest, 
and in most cases, most reliable evaluation is by the trained ob- 
server's visual evaluation of results colored by his knowledge of 
the technique involved." I have made no attempt to precisely quan- 
tify the data, but have discussed it in such relative terms as "no 
contraction," "slight contraction," or "strong contraction." Until 
electromyographic data are available for all the major muscles of 
a particular part of the girdle or limb, or the exact force produced 
can be determined from implanted tension transducers, any at- 
tempt at a more precise quantification easily could be misleading. 
Electromyographic data, however, do allow more accurate anal- 
ysis of the function of many muscles than heretofore has been 

72 



Altenbach — Vampire Locomotor Morphology 73 

possible. All of the literature on the function of muscles in bats is 
centered around predictions about the role of a given muscle based 
on strictly positional criteria. Although reasonably reliable conclu- 
sions can be drawn from positional relationships, they can be nicely 
supplemented and clarified by electromyographic data. 

The temporal lag between myopotential changes and force gen- 
erated by a muscle, which is a function of the time between de- 
polarization and shortening of the fibers and the time required to 
stretch the elastic components of the muscle, probably varies be- 
tween muscles in Desmodus. For the coracoid head of the M. biceps 
brachii, this delay was experimentally determined to be approxi- 
mately 10 milliseconds. A tension transducer was attached to the 
insertional tendon of this muscle and the electromyogram from 
the muscle and output from the transducer were recorded simul- 
taneously with the high-speed camera. Restraints of time and avail- 
ability of additional living specimens for these experiments pre- 
vented doing this with other muscles. When such data are available, 
the electromyographs might be interpreted differently. However, 
as presently interpreted, they provide considerable insight about 
the function of muscles in the pectoral girdle and limb. 

The points on the electromyographic traces in Figs. 32-33, and 
35-41 coincide temporally with corresponding drawings of the lo- 
comotor behavior. Both the electromyogram and drawings are la- 
beled with upper case letters. The probable time of muscular con- 
traction, represented by a solid line, is displaced to the right along 
the horizontal axis of the electromyogram, a distance correspond- 
ing to 10 milliseconds. A scale indicating the magnitude of the 
potential changes on the vertical axis and time on the horizontal 
axis is included in each figure. 

Muscles Unique to Bats 

M. occipito-poUicalis (Figs. 42, 44). — The anatomical modification 
of this muscle in Desmodus seems quite different from that in other 
bats (Macalister, 1872; Humphry, 1869; Vaughan, 1959; Norberg, 
1970/;). There is considerable variability between species in the 
relative length of the fleshy belly distal to its origin on the cranium, 
and in some bats, such as Plecotus auritus (Norberg, 19706) and 
Pteropus edwardsi (Humphry, 1869), there is a second, distal belly. 



74 Spec. Publ. Amer. Soc. Mamm. 6 

However, descriptions of this distal belly indicate it is relatively 
fusiform and originates almost entirely on the rather compact in- 
sertional tendon of the proximal belly, which runs along the lead- 
ing edge of the propatagium (Fig. 24). In Desmodiis, the proximal 
belly inserts rather diffusely into the proximal propatagium. A 
broad, flat belly originates from fibers in the anterior half of the 
propatagium anterior to the radius, about one-third the distance 
toward its distal tip, and from some of the small insertional tendons 
of the proximal belly. Schuinacher (1932) described a M. propa- 
tagialis proprius in Pteropus that was innervated by nerves of the 
cranial portion of the brachial plexus, whereas Macalister (1872) 
found the proximal belly in three other genera to be innervated 
by the spinal accessory nerve. I was unable to trace the innervation 
of either muscle, but on strictly positional criteria, I designate the 
proximal belly as M. occipito-pollicalis and the distal belly as M. 
propatagialis proprius. 

Origin is primarily on connective tissue lateral to the midline 
from the posterior tip of the saggittal crest and down the supraoc- 
cipital for 2 mm. A distal slip originates from fibers of the clavicular 
M. pectoralis. Insertion is by a finely branched tendon onto the 
connective tissue fibers of the propatagium at the level of the base 
of the forearm. 

In contrast to the condition in most other bats, the M. occipito- 
pollicalis tenses the propatagium directly by drawing its elastic fi- 
bers anteromediad. As in other bats, it depresses and tightens the 
leading edge of the propatagium. Contraction of the fibers of the 
clavicular M. pectoralis, which insert on this muscle, draws the me- 
dial half of the propatagium strongly ventrad and increases the 
camber of the medial portion of the wing. 

M. propatagialis proprius (Fig. 46). — The origin is from the fibers 
in the anterior half of the middle propatagium and on some of the 
insertional fibers of the M. occipito-pollicalis. Insertion is by an apo- 
neurosis over the medial aspect of metacarpal I, a thin tendon to 
an aponeurosis over the metacarpophalangeal joint of digit I, and 
a tendon on the middle of the anterior surface of the first phalanx 
of digit II. 

This muscle is not effective in moving the digits, but uses them 
as a fulcrum to tense the propatagium. The vertical orientation of 
the wing during the first half of the upstroke and its position an- 
terior to the body may have necessitated the development of this 



Altenhach — Vampire Locomotor Morphology 75 

muscle. When the wing is highly flexed in this phase of the up- 
stroke, contraction of the M. occipito-pollicalis would have only lim- 
ited effect if it inserted on the hand. However, tension from both 
proximal and distal sides of the propatagium, directed against the 
fibers posterior to the leading edge, is effective in reinforcing it 
for a firm airfoil. Contraction of both muscles at the start of the 
coasting phase of the jump would keep the propatagium oriented 
ahead of the arm and somewhat reduce its area and drag. This 
muscle also serves to help brace the leading edge of the medial 
wing as it is deeply pronated for thrust production in the down- 
strokes during accelerating flight. 

M. coraco-cutaneus (Fig. 44). — Origin is on the medial aspect of 
the tip of the coracoid process of the scapula. The belly gives rise 
to a second belly about 5 mm distal to the origin on the coracoid 
process, and both bellies insert onto elastic fibers in the plagiopa- 
tagium posterior to the brachium and proximal one-fourth of the 
forearm. 

When the wing is adducted in the downstroke, contraction helps 
reinforce the plagiopatagium and reduce billowing from the force 
of the air stream. In the first half of the upstroke, when the distal 
half of the wing is oriented vertically and raised anterior to the 
body (Fig. 20), contraction of this muscle and pull from the hind 
limbs probably help maintain tension on the plagiopatagium to 
reduce its surface area and minimize drag. 

Muscles of the Pectoral Girdle and Limb 

Trapezius Group 

M. clavotrapezius (Fig. 42). — This muscle has its origin on a tough 
tendinous sheet bound to the anterior tip of the dorsal process on 
the first thoracic vertebra and to a dorsal tubercle on the first rib. 
It inserts over the dorsal surface of the clavicle, beginning about 
9 mm distal to its proximal tip and continuing to within 2 or 3 mm 
of its distal tip. 

In contrast to the condition in many other species of bats, the 
clavotrapezius is separate from the acromiotrapezius. It is much 
larger than the anterior portion of the united clavotrapezius and 
acromiotrapezius, which insert on the clavicle of other species. 
Contraction pulls the distal end of the clavicle, and thus the an- 
terior end of the scapula, dorsomedially. The relatively free artic- 



76 Spec. Publ. Amer. Soc. Mamm. 6 








A B C D E F 

Fig. 32. Electromyogram of right M. davotrapezius of Desmodus and correspond- 
ing locomotor behavior. The contraction of the muscle occurs slightly after the 
electrical event and is shown as a solid line above the electromyographic recording. 
Corresponding locomotor stages and portions of the electromyogram are indicated 
by the same letters. 



ulation of the scapula and clavicle of Desmodus requires that the 
clavicle be firmly braced to provide a solid fulcrum on which the 
scapula can rock about its long axis, as described in other species 
of bats by Vaughan (1959). However, more importantly, the an- 
terior tip of the scapula, and thus the shoulder joint, can be pulled 
dorsomediad by this muscle. This movement is important in Des- 
modus to position the wing prior to the first downstroke after a 
jump. The shoulder is pulled ventrad during the jump and must 
be positioned dorsally to give the ventral flight musculature a good 
mechanical advantage on the downstroke. Electromyographic data 
illustrate that the contraction of this muscle probably occurs during 
the powered phase of the jump to stabilize the clavicle. Assuming 
a 10 millisecond temporal lag between the myopotential changes 
and the generation offeree by the muscle, power should be applied 
roughly from before B, through C, and nearly to D in Fig. 32. The 
contraction could certainly be overpowered by the M. subclavius 
during any of the powered phase of the jump, although the qui- 
escence before and after D indicates probable shoulder joint 
depression late in the jump. The jump on which electromyograph- 
ic data are available did not lead to flight (the bat landed on the 
side of the flight chamber after the jump). Thus, the flick and 
subsequent first downstroke do not occur and the contraction to 



Altenbach — Vampire Locomotor Morphology 77 






I I I I I I I I I I I I I I I III 
ABCDEFGH IJ KLMNO PQR 

Fig. 33. Electromyogram of right M. spinotrapezius of Desmodvj and correspond- 
ing locomotor behavior. The contraction of the muscle occurs slightly after the 
electrical event and is shown as a solid line above the electromyographic recording. 
Corresponding locomotor stages and portions of the electromyogram are indicated 
by the same letters. 



78 Spec. Publ. Amer. Soc. Mamm. 6 

raise the clavicle and shoulder from the adducted position is not 
seen. A short burst of activity after the powered phase of the jump 
might be the beginning of such a contraction. 

M. acromiotrapezius (Fig. 42). — The origin is on the dorsal midline 
from the posterior tip of the tubercle on the first thoracic vertebra 
to the posterior tip of the fifth thoracic vertebra. Insertion is onto 
the tendon of origin of the M. acromiodeltoideus from a point about 
half a millimeter anterior to the tip of the acromial process and 
posteriorly for 7.5 mm along the lateral aspect of the acromial 
process and scapular spine. 

The anterior portion of the acromiotrapezius, which inserts on 
the enlarged area of the acromion process, is three times as thick 
as any portion posterior to it. The combined clavotrapezius and 
acromiotrapezius is thicker anteriorly in many other bats 
(Vaughan, 1959; Norberg, 1970^), but the thickened anterior por- 
tion is usually considered the M. clavotrapezius. In Desmodus, the 
thick anterior portion is suited to powerfully tip the acromial pro- 
cess mediad and thus the medial scapular border ventrad, inde- 
pendent of movement of the clavicle. As Vaughan (1959) noted, 
this action can initiate abduction of the humerus when the latter 
is locked with the ventral scapular border. In addition, this muscle 
probably helps steady the scapula when the bat is moving on the 
ground and the lateral scapular border is tipped strongly ventrally. 

M. spinotrapezius (Fig. 42). — Origin is on the dorsal midline from 
the eighth thoracic vertebra to the posterior tip of the second lum- 
bar vertebra. Insertion is from the dorsolateral aspect of the thick- 
ening at the junction of the spine and medial scapular border to 
a point about 5 mm anterior. 

As in other bats (Vaughan, 1959; Norberg, 1970^), this muscle 
is situated to exert a strong posterior pull on the medial scapular 
border. This is important, because the fulcrum of scapular motion 
is the anterior articulation with the clavicle. A posterior anchor is 
necessary if the muscles applying ventral force to the medial and 
lateral scapular borders are to be effective in rocking the scapula 
and the wing when the humerus and scapular border are locked. 
Assuming a 10 millisecond temporal delay, electromyographic data 
illustrate continuous, probably moderate, contraction during the 
jump and quiescence at its end (Fig. 33A-F). Activity during the 
coasting phase may reflect initial limb abduction and scapular sta- 
bilization (Fig. 33G-J), but it is much better positioned for the 



Altenbach — Vampire Locomotor Morphology 79 

latter. However, the relatively great activity around G suggests this 
muscle may be important in reorienting the scapula after its lateral 
border is so highly depressed during the jump. The posteriorly 
elongate scapula in this species is a feature that aids scapular sta- 
bilization by the M. spinotrapezius during movements in flight and 
terrestrial locomotion. Function in the former role is suggested by 
nearly continuous activity during the next two wingbeats (Fig. 
33K-R). 

Costo-spino-scapular Group 

M. levator scapulae (Fig. 42). — The origin of this muscle is by four 
slips onto the dorsal projections of the transverse processes of the 
fourth through seventh cervical vertebrae. Insertion is on the me- 
dial scapular border, beginning about 5 mm posterior to the an- 
terior tip of the scapular flange and continuing posteriorly to the 
junction of the spine and medial border. 

As in other bats (Vaughan, 1959; Norberg, 1970/>), this muscle 
tips the medial scapula border ventrad and, along with the M. 
acromiotrapezius and the anterior division of the M. serratus anterior, 
can brace the scapula or aid in the upstroke. The deep, ventral 
arch of the cervical vertebrae and the relatively high position of 
the scapula separate the origin and insertion of this muscle more 
than in most bats and allow it to exert nearly constant force, ir- 
respective of the position of the scapula. 

M. serratus anterior, anterior division (Figs. 42, 45). — The origin 
of the muscle is by two large bellies: one from the anterior face of 
the first rib adjacent to its articulation with the first costal cartilage, 
and the other by a slip from a tubercle lateral to the transverse 
foramen of the sixth cervical vertebra and a slip from a tubercle 
ventral to the dorsal projection on the transverse process of the 
seventh cervical vertebra. Insertion is onto the medial scapular 
border from the anterior tip of the flange posteriorly to within 
about 4 to 5 mm of the junction of the spine and medial border. 

The anterior portion of the serratus, anterior division, is thick; 
the posterior portion is thin and membranous. Thus, most of the 
contractile force is exerted on the enlarged scapular flange and 
tilts the medial border ventrad. Along with the M. levator scapulae, 
M. acromiotrapezius, and M. rhomboideus, this muscle aids in abduc- 
tion of the arm when the humerus is locked ventrally with the 



80 Spec. Publ. Amer. Soc. Mamm. 6 




subclavius 



M. serratus anterior 
post. div. 



pectoralis 
sternal div. 

Fig. 34. Diagram of anterior view of the rib cage, pectoral girdle, and proximal 
end of the humerus of Desmodus showing primary adductive forces during the 
powered phase of a jump or during the downstroke in initial flight following a 
jump. The humerus is dorsally locked with the scapular border. 



lateral scapular border and probably steadies the scapula during 
jumping behavior and terrestrial locomotion. 

M. serratus anterior, posterior division (Figs. 34, 42, 44-45). — The 
origin extends from the lateral aspect of the first costal cartilage 
in a line along the junctions of the second through sixth ribs and 
their costal cartilages, then dorsally along the costal cartilages of 
ribs seven and eight to the level of the junction of rib eight and its 
costal cartilage. Insertion is on the lateral and ventral aspect of the 
lateral scapular border, from the posterior tip of the posterior 
cartilaginous extension anteriorly to within about 3 mm of the 
glenoid fossa. 

As in other bats (Macalister, 1872; Vaughan, 1959; Norberg, 



Altenbach — Vampire Locomotor Morphology 81 

1970^), the posterior division of the serratus is massive. When the 
humerus is locked with the dorsal scapular border, this muscle can 
adduct the brachium, as in the first portion of the downstroke or 
in much of the powered phase of the jump (Fig. 34). A tremendous 
amount of power is required in the jump to accelerate the bat 
upward with a heavy load of blood. This muscle is probably able 
to assist the sternal M. pectoralis in this movement through an arc 
of more than 130 degrees. 

The posterior division of the M. serratus anterior also is vital in 
the first of the downstroke where it assists the M. pectoralis in ad- 
ducting the extended wing, as described by Vaughan (1959) in 
other bats. Following a jump, air speed is low and the first few 
wingbeats must rapidly accelerate the bat. By functioning simul- 
taneously in the first half of the downstroke, the posterior division 
of the M. serratus anterior and the M. pectoralis supply maximal 
power to the wing when it is configured to provide both thrust and 
lift. During faster and more efficient flight, a division of labor, 
suggested by Vaughan (1959) for other species of bats, between 
the M. serratus anterior, M. pectoralis, and M. subscapularis may occur 
and the muscles may not contract simultaneously. 

During terrestrial locomotion, forces acting on the pectoral limb 
are transferred to the lateral scapular border by the humerus. 
During locomotion with the body extremely elevated, as seen in 
terrestrial feeding behavior, this muscle tips the short axis of the 
scapula nearly vertically, thus directing the forces acting against 
the pectoral limbs directly upward against the scapula, with little 
or no rotational component. The M. serratus anterior and the clav- 
icle thus act as a sling to support the body. 

M. rhomboideus (Fig. 42). — The origin is a large belly from tho- 
racic vertebrae one through six; a small anterior slip on the ten- 
dinous sheet that is the origin of the M. clavotrapezius; and a third 
slip on the dorsal spinal musculature adjacent the first thoracic 
vertebra. Insertion is on the ventral and medial aspect of the pos- 
terior cartilaginous extension of the scapula and anteriad along 
the medial scapular border to its junction with the scapular spine. 

Thin anteriorly, the rhomboideus becomes thick posteriorly in 
the region of its insertion on the posterior cartilaginous extension 
of the scapula. This suggests the major function is to shift the 
scapula anteriad and tilt its medial border ventrad. As in other 
bats (Vaughan, 1959; Norberg, 19706), this muscle functions with 



82 Spec. Publ. Amer. Soc. Mamm. 6 







AA 










»-'»v^\j|^I^W~- 



-^^\^w^ 



Q R S T U 20msec 

Fig. 35. Electromyogram of right M. latissimus dorsi of Desmodus and corre- 
sponding locomotor behavior. The contraction of the muscle occurs slightly after 
the electrical event and is shown as a solid line above the electromyographic re- 
cording. Corresponding locomotor stages and portions of the electromyogram are 
indicated by the same letters. 



Altenbach — Vampire Locomotor Morphology 83 

the M. acromiotrapezius, M. levator scapulae, and the anterior division 
of the M. serratus anterior to power the initial abduction of the arm 
or to steady the scapula when contracting against the antagonistic 
posterior division of the M. serratus anterior. Anteroposterior move- 
ments of the scapula probably aid in balancing the bat over the 
line of force exerted by the pectoral limbs during a jump and in 
stabilizing the shoulder girdle during turning maneuvers (Fig. 18). 

M. omocerzncalis (Fig. 42). — Origin is on the ventral arch of the 
atlas. Insertion is onto the dorsal border of the clavicle and half a 
millimeter of the adjacent M. subclavius, 7 mm distal to the sternal 
articulation of the clavicle. 

The omocervicalis probably aids in the movement of the head. 
Insertion on the central clavicle instead of the acromial process (as 
in many other bats) is indicative of the great motility of the head 
in this species. 

Latissimus-subscapular Group 

M. latissimus dorsi (Fig. 42). — Origin is on the dorsal midline from 
the posterior tip of thoracic vertebra nine to the anterior tip of 
lumbar vertebra three. Insertion is in common with the M. teres 
major on the low ridge on the ventral aspect of the humerus be- 
ginning about 3.5 mm distal to the tip of the lesser tuberosity. 

The latissimus dorsi and the teres major are well suited to pro- 
nate the humerus and thus the entire arm, as well as to flex and 
abduct the humerus. These movements are important in terrestrial 
locomotion when the pectoral limbs are pulled posteriad and pro- 
nated in the power stroke. Figure 35 illustrates the function of this 
muscle during a jump into flight and the initial two wingbeats. A 
10 millisecond temporal delay between myopotential changes and 
contraction is assumed. Contraction begins at the onset of the 
coasting phase (Fig. 35E) and probably helps abduct the wing. 
During the early part of the initial flick (Fig. 35H), contraction 
helps pronate the arm to drive the digits upward and backward 
against the airstream and help position the wing for the first down- 
stroke. Slight electrical activity indicates weak contractions during 
the downstroke that perhaps help stabilize the angle of attack and 
may reinforce the strong pronation of the wing. After flexion and 
supination of the arm in the first of the upstroke, sudden con- 
traction helps pronate and abduct the arm early in the flick phase 
(Fig. 35L to between M and N). This myopotential burst indicates 



84 Spec. Publ. Amer. Soc. Mamm. 6 

Strong, perhaps maximal, contractive force during this movement. 
Feeble contractions again occur periodically during the down- 
stroke, perhaps for fine control of wing orientation, and a strong 
contraction occurs early in the flick phase (Fig. 35R to between S 
and T). 

M. teres major (Fig. 42). — Origin is on the lateral scapular border 
from the level of the junction of the spine and medial border to 
within about a millimeter of the posterior tip. Insertion is with the 
M. latissimus dorsi on the ventral aspect of the humerus distal to the 
lesser tuberosity. 

The function of the teres major is essentially similar to that of 
the M. latissimus dorsi, except that it is not suited to abduct the 
humerus. It probably functions primarily in the flick phase of the 
upstroke in flight, in terrestrial locomotion, and in climbing. 

M. subscapularis (Fig. 45). — Origin is on the ventral aspect of the 
scapula and posterior cartilaginous extension to within 2 mm of 
the base of the coracoid process and within 2 mm of the posterior 
edge of the glenoid fossa. Insertion is onto the posterior and me- 
dial aspect of the tip of the lesser tuberosity of the humerus. 

Although no electromyographic data are available, the subscap- 
ularis almost certainly functions to adduct the humerus after it is 
unlocked from the dorsal scapular border in the last of the down- 
stroke in forward flight, as described by Vaughan (1959). In an 
alighting maneuver (Fig. 23), the subscapularis, along with the cla- 
vicular M. pectoralis, extends and adducts the humerus prior to 
contact of the substrate by the forelimbs and probably helps cush- 
ion the impact by contraction as the humerus is forced upward 
and backward. 

Deltoid Group 

M. clavodeltoideus (Figs. 42, 44). — Origin of a large belly is from 
the anterodorsal aspect of the clavicle for about 9 mm beginning 
approximately 2.5 mm from its distal tip; and a small belly, deep 
to the first, from about 2 mm of the anteroventral surface of the 
clavicle in the region of the sharp posterior curve of the clavicle 
before its articulation from the scapula. Insertion of the larger 
belly is onto the anterior aspect of the expanded proximal tip of 
the pectoral ridge and laterally for 9 mm. The second belly inserts 
onto the dorsomedial aspect of the proximal end of the pectoral 



Altenbach — Vampire Locomotor Morphology 85 

ridge and onto a ridge on the anterior base of the greater tuber- 
osity. 

Both bellies are clearly separate from the clavicular portion of 
the M. pectoralis. The clavodeltoideus powers the forward, recovery 
stroke of the brachium during terrestrial locomotion and the 
thrusting stroke of the brachium during backward climbing. It is 
probably aided in this movement by the clavicular M. pectoralis and 
somewhat by the M. subscapularis. Its clear separation from the 
clavicular M. pectoralis suggests that the clavodeltoideus is impor- 
tant in powering the complex movements of terrestrial locomotion 
and climbing. 

The clavodeltoideus cannot assist in adduction of the brachium 
during the powered phase of the jump or in the downstroke of 
forward flight, but it is important in controlling the angle through 
which adduction progresses. Steady contraction during a down- 
stroke would direct the stroke strongly forward. In a braking ma- 
neuver, this muscle functions to anteriorly brace the wing as it 
remains extended at a high angle of attack. 

M. acromiodeltoideus (Fig. 42). — The origin is on the tendon of 
insertion of the M. acromiotrapezius at a point anterior to the acro- 
mion process and extending for 6 mm along the lateral aspect of 
the acromion process and scapular spine. Insertion is on the an- 
terior 2 mm of the dorsal aspect of the pectoral ridge beginning 
5 mm distal to the tip of the greater tuberosity and continuing 
lateral for 1 1 mm. 

The acromiodeltoideus is situated to abduct, slightly flex, and 
impart a strong supinating force to the humerus. The relatively 
long scapula, along with bracing supplied by the M. spinotrapezius, 
provides a stable origin for the muscle to supinate the brachium 
and thus raise the wing when the forearm is flexed toward the 
brachium, as occurs at the beginning of the upstroke. An electro- 
myographic record during a jump and initial flight indicates a 
relatively long contraction during the adduction of the brachium 
(Fig. 36D-G). This seems surprising, but possibly the acromiodel- 
toideus stabilizes the dorsal locking of the scapula and humerus 
throughout the entire powered phase of the jump, thus suggesting 
that the humerus is not adducted relative to the scapula during 
even the last of the jump. The posterior division of the M. serratus 
anterior and the sternal M. pectoralis thus would supply the power 
for the entire adduction of the brachium. The relatively free ar- 



86 Spec. Publ. Amer. Soc. Mamm. 6 



oV 



^/% (zljK '^if% '^^fx ""^Z 

A B C D E 






f', 



2 tnv 


P 

20 msec 


Q 








1 1 1 1 
J K L M 






1 

A 


1 1 1 1 1 1 1 1 
B C D E F G H 1 


1 
N 


1 r 1 
P Q 



Fig. 36. Electromyogram of right M. acromiodeltoideus of Desmodus and corre- 
sponding locomotor behavior. The contraction of the muscle occurs slightly after 
the electrical event and is shown as a solid line above the electromyographic re- 
cording. Corresponding locomotor stages and portions of the electromyogram are 
indicated by the same letters. 



Altenbach — Vampire LtPcomotor Morphology 87 

ticulation of the scapula and clavicle allows the two largest muscles 
in the bat to power the adduction of the brachium during the 
jump. The M. subscapularis apparently does not aid the adduction 
during the jump as perhaps it does in the downstroke of forward 
flight, as Vaughan (1959) suggested for other bats. However, the 
electromyographic data provide no evidence that the M. subscap- 
ularis does not overpower the deltoid group and adduct the hu- 
merus relative to the scapula at the very last of the powered phase 
of the jump. 

Contraction of the M. acromiodeltoideus probably continues dur- 
ing the first part of the coasting phase of the jump, or until the 
initiation of the flick phase (Fig. 36, between G and H). Activity 
depicted at Fig. 361 suggests the muscle again stabilizes the dorsal 
locking of scapula and humerus prior to the downstroke. Only 
slight activity is apparent in the first downstroke, but contraction 
again occurs at the last of the downstroke and onset of the up- 
stroke, and continues to the initiation of the flick phase (Fig. 36, 
K to between L and M). Contraction at the end of the upstroke 
again indicates stabilization of dorsal locking of scapula and hu- 
merus. The muscle probably functions to supinate and abduct the 
brachium during the very last of the downstroke and first half of 
the upstroke. Final positioning of the brachium prior to the down- 
stroke appears to be the function of the M. latissimus dorsi and M. 
teres major. 

M. spinodeltoideus (Fig. 42). — Origin is by a tendinous raphe over 
the scapular spine and then along the dorsal aspect of the thick- 
ened medial scapular border to its posterior tip. Insertion is by a 
flat tendon posterior to the proximal 2.5 mm of the insertion of 
the M. acromiodeltoideus. 

The spinodeltoideus is relatively thin and situated to slightly 
abduct, flex, and supinate the humerus. An electromyographic re- 
cording during a jump into flight (Fig. 37) illustrates contractions 
similar to those of the M. acromiodeltoideus (Fig. 36). Initially, there 
is a contraction that, along with the other deltoid muscles, probably 
stabilizes the locking of the humerus and dorsal scapular border. 
The contraction continues during the powered phase of the jump, 
but becomes less intense over the last half of the adduction of the 
brachium (Fig. 37F). At the beginning of the coasting phase (Fig. 
37G), contraction aids the supination and perhaps the abduction 
of the brachium. In the flick phase, shght contraction apparendy 



spec. Publ. Amer. Soc. Mamm. 6 



Mh^ Mh^ £^ J^ Jh^ 



A 



m^ w 



fr 





I t I I I I I I I I I I I I I I I I 



H I 



M N 



Fig. 37. Electromyogram of right M. spinodeltoideus of Desmodus and corre- 
sponding locomotor behavior. The contraction of the muscle occurs slightly after 
the electrical event and is shown as a solid line above the electromyographic re- 
cording. Corresponding locomotor stages and portions of the electromyogram are 
indicated by the same letters. 



Altenbach — Vampire Locomotor Morphology 89 

helps pull the brachium mediad prior to the downstroke (Fig. 371- 
J). The supinating force imparted by this contraction is probably 
offset by the pronating force of the M. latissimus dorsi, M. teres 
major, and M. pectoralis. With the wing at the level of midbody, 
another contraction occurs that probably tends to reduce some of 
the pronation imparted by the M. pectoralis and conforms the wing 
into more of a lift-generating structure (Fig. 37K to between L and 
M). As the humerus probably is locked with the dorsal scapular 
border at this point, this contraction does not detract from the 
adductive forces applied to the brachium. The contraction contin- 
ues into the first phase of the upstroke to help supinate the wing 
and again in the flick phase to position the brachium for the down- 
stroke. Another contraction early in the downstroke (Fig. 37P-Q) 
probably reinforces the scapulo-humeral locking and stabilizes the 
arm against some of the pronating force applied by the M. pecto- 
ralis. 

M. teres minor. — The origin is on the posterodorsal aspect of the 
rim of the glenoid fossa and onto the tendon of origin of the long 
head of the M. triceps brachii. Insertion is on the dorsal surface of 
the greater tuberosity of the humerus for 1.5 mm distal to the 
insertion of the M. infraspinatus. The small teres minor is a weak 
supinator and flexor of the humerus. 

Suprascapular Group 

M. supraspinatus (Fig. 42). — The origin is from the medial 3 mm 
of the supraspinous fossa and adjacent ligamentous raphe over the 
scapular spine, and from the dorsolateral aspect of the scapular 
flange. Insertion is by a heavy tendon onto a groove on the medial 
surface of the greater tuberosity of the humerus. 

As in other bats (Vaughan, 1959; Norberg, 1970^), the supra- 
spinatus abducts, slightly supinates, and extends the humerus. 
Along with some of the deltoid group (Figs. 36-37), it probably 
stabilizes the dorsal locking of the scapula and humerus and helps 
abduct the humerus relative to the scapula during the upstroke in 
forward flight. In terrestrial locomotion, it is best suited to swing 
the humerus forward and, by supinating and slightly abducting 
the humerus, to lift the carpus off the substrate for the forward 
swing. In terrestrial feeding postures, when the short axis of the 
scapula is oriented nearly vertically, this muscle, along with the M. 



90 Spec. Publ. Amer. Soc. Mamm. 6 

infraspinatus and M. subscapularis, is important in moving the pec- 
toral limb. 

M. infraspinatus (Fig. 42). — Origin is from the lateral aspect of 
the scapular spine; lateral aspect of the medial border posterior to 
the spine; dorsal base of the posterior caritilaginous extension; 
medial aspect of the lateral border to within 3 mm of the origin 
of the M. triceps brachii, long head; and surfaces of the three facets 
(Fig. 26). Insertion is by a thick tendon, a millimeter wide, onto 
the dorsal aspect of the tip of the greater tuberosity of the hu- 
merus. 

The posteriorly elongate scapula in Desmodus positions the origin 
of the infraspinatus relatively far posterior to the insertion. The 
insertion on the dorsal aspect of the greater tuberosity also is dis- 
placed well above the fulcrum at the center of the head. Thus this 
muscle is the most powerful supinator of the brachium and no 
doubt functions in the last part of the downstroke and first part 
of the upstroke to raise the forearm and hand anteriorly to the 
body. As this muscle is not situated to provide much abductive 
force to the humerus, it is probably relatively important in the last 
half of the downstroke in counteracting the pronating forces ap- 
plied by the M. pectoralis, and helps position the wing into a lift- 
generating configuration (Fig. 19). 

Triceps Group 

M. triceps brachii, caput lateralis (Fig. 43). — The origin is from a 
strip a millimeter wide along the posterior surface of the humerus 
beginning at the base of the lesser tuberosity and extending dor- 
sally to the level of the top of the head. Insertion is by a large 
sesamoid onto the olecranon process of the ulna. 

M. triceps brachii, caput medialis (Fig. 43). — The origin extends 
over 13 mm of the posterodorsal surface of the humerus beginning 
2 mm lateral to the head. A second group of short fibers, assumed 
to be part of this head, originates along the posterior aspect of the 
distal half of the humerus and inserts into the common tendon to 
the olecranon process of the ulna. Insertion is by a large sesamoid 
onto the olecranon process of the ulna. 

M. triceps brachii, caput longus (Fig. 43). — Origin is by two slips 
from the two tubercles, 1.5 mm apart, posterior to the posterior 
border of the glenoid fossa of the scapula. Insertion is by a large 
sesamoid onto the olecranon process of the ulna. 



Altenbach — Vampire Locomotor Morphology 91 



A B 





3^ 



^^^ 4%. jf- 



E 



f^^ 



-"^ 



^ 



m 





I I I I I I I I I I I > I 

ABCDEFGHIJKLMNOPQR 

20 msec 
Fig. 38. Electromyogram of right M. triceps brachii, long head, of Desmodus and 
corresponding locomotor behavior. The contraction of the muscle occurs slightly 
after the electrical event and is shown as a solid line above the electromyographic 
recording. Corresponding locomotor stages and portions of the myogram are in- 
dicated by the same letters. 



92 Spec. Publ. Amer. Soc. Mamm. 6 

An electromyographic record of the long head of the triceps 
muscle during a jump into forward flight reveals a contraction that 
begins during the inclination of the brachium and continues until 
contact with the substrate is broken (Fig. 38B-G). After only a 
short period of quiesence during the first of the coasting phase 
(Fig. 38G-H) when contraction of the M. biceps brachii flexes and 
begins supination of the forearm (Fig. 40G-H), contraction begins 
to extend the forearm (Fig. 38H-I). The electromyogram shows 
an increase in amplitude that probably represents greater strength 
of contraction during the flick phase (Fig. 38I-K), where the fore- 
arm is fully extended along with the digits to provide forward 
thrust and to help position the wing for the first downstroke. The 
contraction continues during the first half of the downstroke and 
maintains the full extension of the arm (Fig. 38K-M). Past the level 
of midbody, contraction ceases and the M. biceps brachii (Fig. 40L- 
N) begins flexion of the forearm that continues through the first 
third of the upstroke. Contraction of the triceps begins at about 
the second third of the upstroke, stops for a few milliseconds, and 
then continues during the flick phase and the first half of the next 
downstroke (Fig. 380-R). 

Although the electrodes were in the long head of the triceps, 
one of the leads was near (and possibly may have contacted) the 
posterodorsal aspect of the lateral head, and may have monitored 
some of its electrical activity. Although the function of the three 
heads may be slightly different, the nearly inseparable contact of 
the bellies, the close approximation of the origin of the long, lat- 
eral, and most of the medial head, and their common insertion on 
the olecranon process, suggest that their action is functionally and 
temporally quite similar. The long head may function to slightly 
flex the brachium but, because the mechanical advantage is poor 
for this movement, it could be easily counteracted by the scapular 
musculature. 

The large sesamoid in the insertional tendon is contoured to fit 
closely the concavity on the posterior side of the distal articular 
surface of the humerus and suggests that considerable tension is 
applied by this muscle group. The jump is certainly the most de- 
manding of the triceps, as it is the third largest muscle powering 
the jump and since it must move the forearm through an arc of 
about 140 degrees. 



Altenbach — Vampire Locomotor Morphology 93 
Extensor Group of the Forearm 

M. extensor carpi radialis brevis (Figs. 46, 48). — The origin is by a 
tough tendon on the medial edge of the dorsal epicondyle of the 
humerus. Insertion is on a large tubercle on the anterodorsal base 
of metacarpal III by a heavy tendon and onto the dorsolateral tip 
of the trapezium by a rather elastic band of connective tissue. 

By extending the third digit, this muscle extends the fifth digit 
and aids the M. extensor carpi radialis longus in extending the re- 
mainder of the hand-wing. A detailed discussion of both muscles 
is included with the discussion of the M . extensor carpi radialis longus 
below. 

M. extensor carpi radialis longus (Figs. 46-48). — Origin is by a 
heavy tendon on the medial aspect of the dorsal epicondyle of the 
humerus. Insertion is onto the anterodorsal base of metacarpal II 
and into a depression in the lateral base of metacarpal I by a heavy 
tendon. 

In Desmodus, as in other species of bats (Vaughan, 1959; Nor- 
berg, 1970^), this muscle and the adjacent M. extensor carpi radialis 
brevis are the largest muscles in the forearm. Although their origins 
are displaced mediad to the center of rotation of the elbow joint, 
the extremely large size of the bellies and the lack of a tough 
connective tissue covering found in many other bats suggests that 
these muscles are well suited to act independently of movements 
at the elbow. Vaughan (1959) pointed out that in other species of 
bats, such as Eumops perotis, Myotis velifer, and Macrotus waterhousii, 
these muscles can act as relatively inelastic bands and automatically 
extend the chiropatagium as the elbow is extended. This helps 
concentrate the weight toward the body and eliminate weight in 
the wing. The terrestrial propensity of Desmodus, and particularly 
its jumping behavior, necessitate complete independence of move- 
ments of the hand from movements of the rest of the arm, al- 
though there appears to be a sacrifice of added weight in the wing. 
The muscles are certainly stretched by extension of the elbow, but 
the elastic components appear to absorb this movement and allow 
the hand to remain folded against the forearm. This feature may 
help explain the strong and mechanically advantageous insertion 
of some of the flexors of the hand that have to hold the hand 
flexed while the arm is fully extended, as in terrestrial feeding 



94 Spec. Publ. Amer. Soc. Mamm. 6 







■L 



Fig. 39. Electromyogram of right M. extensor carpi radialis longus of Desmodus 
and corresponding locomotor behavior. The contraction of the muscle occurs 
slightly after the electrical event and is shown as a solid line above the electromy- 
ographic recording. Corresponding locomotor stages and portions of the myogram 
are indicated by the same letters. 



Altenbach — Vampire Locomotor Morphology 95 

posture or in the powered phase of the jump. This muscle begins 
contraction during the powered phase of the jump and continues 
until late in the first downstroke (Fig. 39, B to between I and J). 
Shortly after the start of the coasting phase (Fig. 39E), partial ex- 
tension of the digits is evident; however, I cannot fully explain the 
early initiation of contraction. Perhaps co-contraction of antago- 
nists tends to brace the carpus as the thrust of the pectoral limb 
is directed against it and the thumb. The greater number of spikes 
in the electromyogram indicate that the contraction during the 
flick phase is stronger than that before it, suggesting that perhaps 
the movement meets considerable resistance. 

The muscle is quiescent in the last of the downstroke and first 
half of the upstroke (Fig. 39I-K), but contracts during the last of 
the flick phase and through the first half of the next downstroke 
(Fig. 39, between K and L-N). The sequence of contraction is 
essentially similar during the last of this cycle as in the one pre- 
ceding it. Although no electromyographic data are available for 
the M. extensor carpi radialis brevis, I assume its function is similar 
to that of the M. extensor carpi radialis longus. 

M. supinator (Fig. 46). — Origin is by a heavy tendon onto the 
center of the dorsal (lateral) epicondyle of the humerus. Insertion 
is over 10 mm of the anterior surface of the radius beginning 3 
mm distal to its proximal articular surface. 

As in other bats, this muscle originates by a tendon that contains 
a sesamoid bone and is a flexor of the forearm. The muscle lacks 
good mechanical advantage for this action. Thus it probably func- 
tions mainly to brace and stabilize the elbow joints as strong su- 
pinating forces, applied proximally to the humerus, raise the 
flexed forearm as in the first half of the upstroke (Fig. 20). The 
relatively large size of this muscle suggests the importance of this 
function. 

M. extensor poinds brevis (Fig. 48). — Origin is along 10 mm of the 
interosseus surface of the ulna beginning 3 mm distal to the tip of 
the olecranon process. Insertion is by a tendon heavily bound to 
the anterodorsal aspect of the carpus and metacarpal I, which at- 
taches on the dorsal aspect of the proximal base of the first phalanx 
of digit I. 

This muscle extends the thumb and, if resisted by the flexors of 
the first metacarpal, extends the phalanges of the thumb. Desmodus 
commonly rests much of its weight on the distal pad at the meta- 



96 Spec. Publ. Amer. Soc. Mamm. 6 

carpophalangeal junction of digit I during terrestrial locomotion 
or when standing (Fig. 2), and this muscle is necessary in elevating 
the claw during movements of the limb from this position. When 
Desmodus is walking on a nervous or easily aroused host animal 
prior to feeding, the claws may be elevated to minimize stimulation 
of the skin of the host. 

M. abductor pollicis longus (Fig. 49). — Origin is on 7 mm of the 
interosseus surface of the ulna and along 16 mm of the interosseus 
surface of the radius beginning at the medial contact of the radius 
and ulna. Insertion is by a thick tendon on the anterior tip of the 
scaphoid. The tendon divides proximal to the scaphoid and 
another branch runs forward, inserts onto the ventromedial sesa- 
moid on the distal tip of metacarpal I, and sends fibers into the 
pad at the metacarpophalangeal joint of digit I. 

The tendon, which inserts on digit I, probably is the remnant of 
the M. abductor pollicis brevis, which has become tendinous and 
shifted its origin from the scaphoid directly to the tendon of the 
M. abductor pollicis longus. No doubt the elongation of the first digit 
in Desmodus and its use in jumping have necessitated the reduction 
of the M. abductor pollicis brevis to a tendon. The large and relatively 
long belly of the M. abductor pollicis longus on the forearm is better 
suited to provide power through a wide arc of movement than is 
a shorter and much smaller muscle originating on the hand. By 
becoming tendinous and shifting its origin directly to the tendon 
of the M. abductor pollicis longus, the M. abductor pollicis brevis allows 
more powerful movement of the thumb. Although no electromy- 
ographic data are available, it is evident that the M. abductor pollicis 
longus serves two important functions. Its contraction pulls the 
scaphoid mediad over the lunar and thus puts tension on the M. 
abductor digiti quinti (Fig. 49), which originates from the scaphoid, 
and puts tension on the pisiform itself. As Vaughan (1959) noted, 
this is important in bracing the fifth metacarpal and basal phalanx 
of digit V against upward deflection during adduction of the wing. 
In addition, the M. abductor pollicis longus pulls the first metacarpal 
ventrad and is important in terrestrial locomotion. In terrestrial 
feeding postures, or in terrestrial locomotion with the body held 
high above the substrate, this muscle shifts the weight from the 
basal to the distal thumb pad thus elevating the bat higher. Con- 
traction also aids in keeping the wing folded by flexing the fifth 
digit through tension on the M. abductor digiti quinti. During the 



Altenbach — Vampire Locomotor Morphology 97 

last of the power phase of the jump, the M. abductor pollicis longus, 
along with the M. flexor digitorus profundus and M. palmaris longus, 
pull the thumb ventrad to provide the last upward thrust. In 
addition, all of these muscles produce flexion of at least one digit 
besides the first, thus helping to keep the remainder of the hand 
folded. 

M. extensor digiti quinti proprius (Fig. 48). — Origin is by a thin 
tendon onto the distal edge of the dorsal (lateral) epicondyle of 
the humerus. Insertion is onto the dorsal aspect of the proximal 
tip of the second phalanx of digit V by a broad tendon. 

At the point where this tendon meets the dorsal surface of the 
fifth metacarpal, it is joined by a small tendon of the M. extensor 
digitorum communis. This muscle deflects the phalanges of digit V 
upward and tends to elevate the metacarpal slightly. The relative 
size of the belly and the insertional tendon suggest this movement 
is important. High-speed photographs of Desmodus in flight (Fig. 
19) show that during the first half of the downstroke the phalanges 
of digit V are deflected upward, thus shaping the distal plagio- 
patagium and medial chiropatagium into a thrust-generating 
structure similar to that of the distal chiropatagium. Contraction 
of this muscle, combined with the passive forces from the air pres- 
sure, would cause the upward deflection to be greater than that 
from the air pressure alone and would shape that part of the wing 
into a more efficient thrusting configuration. Simultaneous con- 
traction of the M. abductor digiti quinti, M. opponens digiti quinti, and 
M. abductor pollicis longus would overpower the M. extensor digiti 
quinti proprius, flex the phalanges, depress the metacarpal, and sta- 
bilize the phalanx against the metacarpal. 

M. extensor digitorum communis (Figs. 46, 48). — Origin is by two 
separate bellies with tendinous origin on the dorsal (lateral) epi- 
condyle of the humerus and fleshy origin beginning 6 mm distal 
to the proximal tip of the radius, and extending distad along the 
dorsal surface of the radius for 14 mm. Insertion is through a 
tendon to digit III, which runs along the dorsal aspect of the meta- 
carpal and sends fibers to the proximal tips of the first and second 
phalanges. The primary insertion of the tendon is on the postero- 
dorsal aspect of the proximal tip of phalanx three. The tendon to 
digit IV inserts on a tubercle on the dorsolateral aspect of phalanx 
one, 2 mm distal to the proximal base. 

The tendon to digit IV divides distal to the carpus and sends a 



98 Spec. Publ. Amer. Soc. Mamm. 6 

branch to the tendon of the M. extensor digiti quinti proprius at its 
proximal contact with the metacarpal, thus it aids in dorsal deflec- 
tion of the phalanges of digit V. The connections to digits III and 
IV dorsally deflect the phalanges and slightly deflect the metacar- 
pals. In the downstroke in forward flight (Fig. 19), the M. extensor 
digitorum communis probably aids the force of the air stream in the 
upward deflection of the phalanges to provide the propeller effect 
and upturned configuration of the distal chiropatagium between 
digits III and IV, which perhaps function to reduce tip vortices. 
It also provides downward acceleration of air and lift production 
in the last of the downstroke. More important, however, is the 
function of this muscle in the flick phase of the upstroke. During 
the first of the flick (Fig. 20N-P), when the forearm is extended, 
the phalanges of digits III to V are deflected ventrally by the force 
of the air and perhaps by contraction of the flexors of the digits. 
As the flick nears completion, the phalanges are fully extended to 
provide the last component of forward thrust and help to position 
the wing for the downstroke. This movement appears to be par- 
tially active and not simply the result of upward air pressure as 
adduction begins. 

M. extensor carpi ulnaris (Figs. 46-49). — Origin is from the deep 
groove and adjacent ridge on the proximal 6 mm of the postero- 
ventral surface of the ulna. Insertion is by a heavy tendon on the 
tubercle on the dorsomedial aspect of metacarpal V, 2 mm distal 
to its proximal tip. 

This muscle is a powerful flexor of digit V and, because of lig- 
aments that join the proximodorsal surfaces of metacarpals III and 
V, the entire hand-wing. In the distantly related phyllostomatid 
bat, Macrotus, this muscle inserts on metacarpal V but is an exten- 
sor. In Eumops perotis and Myotis velifer (Vaughan, 1959), this mus- 
cle inserts on metacarpal III and is a flexor. In Plecotus auritus 
(Norberg, 1970^), the muscle inserts on metacarpal III and is an 
extensor. The tendon is the thickest one to the hand, and the belly 
is quite large. When the forearm is extended with the wing folded 
as in terrestrial feeding postures or in parts of the climbing and 
walking cycles (Figs. 2, 4, 6), the large M. extensor carpi radialis 
longus and M. extensor carpi radialis brevis are stretched and apply 
some passive, extensive forces to the hand. This muscle is no doubt 
necessary to resist these forces and keep the wing folded. Inasmuch 
as the radial extensors of Desmodus are not heavily invested in 



Altenbach — Vampire Locomotor Morphology 99 

connective tissue, they are probably rather elastic and thus do not 
explain the need for the massive tendon of the M. extensor carpi 
ulnaris. However, in landing on the ground, it is critical for the 
wing to be quickly folded against the forearm to prevent injury to 
the digits. It is also important for the wing to remain tightly folded 
during terrestrial locomotion. The insertion seems well suited for 
effecting such a rapid and powerful movement. 

M. extensor indicis (Fig. 48). — Origin is on 14 mm of the postero- 
dorsal surface of the radius to within about 4 mm of the distal 
articular surface and on 9 mm of the interosseus surface of the 
ulna, beginning about 8 mm distal to the proximal articulation of 
the radius and ulna. Insertion is at several points. At the level of 
the proximal carpus, the tendon gives rise to a sheet of tendon 
that inserts on the anterodorsal carpus and dorsomedial aspect of 
the proximal half of metacarpal I. Another colateral tendon arises 
from the main tendon and runs to the dorsolateral aspect of the 
distal third of metacarpal I. The main tendon inserts by way of a 
sesamoid on a tubercle on the anterodorsal surface of metacarpal 
II, 3 mm distal to its proximal base. At the level of the sesamoid, 
small tendinous attachments run from the main tendon postero- 
laterad to insert on the dorsal aspect of the bases of metacarpals 
III and IV. 

This muscle functions with the M. extensor carpi radialis longus 
and M. extensor carpi radialis brevis to extend the hand-wing during 
the coasting phase of the jump, and during the flick phase and 
first half of the downstroke in forward flight. The attachments to 
the dorsal aspect of the third and fourth metacarpals suggest it 
also is important in bracing the hand against posterior and dorsal 
air pressure during the flick phase of the upstroke, when the digits 
are extended and the wing is strongly pronated and abducted. The 
attachments to the first digit probably help raise it when the hand 
is flexed by the M. extensor carpi ulnaris, as occurs in terrestrial 
locomotion. 

Pectoralis Group 

M. subclavius (Figs. 44-45).— Origin is by a fleshy attachment to 
the ventral aspect of the first costal cartilage adjacent to its attach- 
ment to the manubrium and by tendinous attachment to the an- 
terolateral border of the first costal cartilage. Insertion is on the 



100 spec. Publ. Amer. Soc. Mamm. 6 

posteroventral surface of the clavicle from its distal tip to within 
2 mm of its articulation with the manubrium. 

Because of the relatively free articulation of the clavicle and 
scapula, this muscle is important in both jumping and flight. Con- 
traction pulls the distal tip of the clavicle ventrad and slightly pos- 
teriad, and can effectively brace the clavicle when co-contracting 
with the M. clavotrapezius. Slight dominance of one or the other 
could swing the clavicle dorsad or ventrad and still stabilize it as 
a solid fulcrum for movements of the scapula and arm. High-speed 
photographs of a jump show that the shoulder joint is depressed, 
and although no direct evidence is available, this movement ap- 
pears to be partly the result of depression of the tip of the clavicle 
by this muscle. The electromyographic data for the M. clavotra- 
pezius (Fig. 32) indicate contraction during all but the last of the 
powered phase of the jump, but such contraction is necessary to 
stabilize the clavicle and could be overpowered by the M. subclavius. 
Seemingly the subclavius is not opposed by the clavotrapezius at 
the last of the powered phase of the jump and probably depresses 
the clavicle. 

M. pectorahs. — This muscle appears to be divided into three ma- 
jor bellies in Desmodus. However, I distinguish only between cla- 
vicular and sternal portions, as the clavicular portion is widely sep- 
arate from the remainder of muscle. As Vaughan (1959) described 
for other species of bats, I have noted considerable individual vari- 
ation in the degree of separation and arrangement of the non- 
clavicular portion and consider it the posterior (sternal) division. 

M. pectorahs, anterior (clavicular) division (Fig. 44). — Origin is on 
the anteroventral aspect of the proximal base of the clavicle and 
along the anterior and ventral aspect of the proximal half of its 
shaft. Insertion is from the dorsal aspect of the medial tip of the 
pectoral ridge, laterally for about 9 mm, superficial to the insertion 
of the posterior (sternal) division of the M. pectorahs. 

The clavicular M. pectorahs pulls the humerus craniad and ad- 
ducts and pronates it slightly. This movement is not part of the 
normal wingbeat cycle or of a jump, but occurs as the limb is 
positioned prior to alighting on a horizontal surface (Fig. 23) and 
in backward climbing (Fig. 6). In terrestrial locomotion, this muscle 
probably functions along with the M. clavodeltoideus to swing the 
humerus forward in the recovery stroke (Fig. 4). When cocontract- 
ing with the sternal division of M. pectorahs, the clavicular division 



Altenbach — Vampire Locomotor Morphology 101 

can assist in adduction and pronation of the humerus and is prob- 
ably responsible for much of the cranial inclination of the path of 
the wing in the last half of the downstroke (Fig. 19). 

M. pectoralis, posterior (sternal) division (Fig. 44). — Origin of one 
belly is on the lateral aspect of the ventral arm of the manubrium, 
the ventral aspect of the lateral arms to within 2 mm of their distal 
tips, and the ventrolateral aspect of the posterior arm; that of the 
other belly is on the ventral aspect of the body of the sternum to 
within 2 mm of the posterior tip of xiphisternum and on a ten- 
dinous raphe over the midline, beginning anteriorly on the tip of 
the ventral arm of the manubrium and extending posterior to the 
posterior tip of the body of the sternum. Insertion is onto the 
ventral half of the anterior face of the proximal end of the pectoral 
ridge and laterally for 10 mm along the anterior and ventral edge 
of the pectoral ridge. 

The bellies of this massive muscle are the major adductors and 
pronators of the humerus, and consequently of the arm and hand. 
The origin over the manubrium, body, and xiphoid process of the 
sternum makes this muscle effective in moving the humerus 
through a variety of planes, as Vaughan (1959) pointed out for 
other species. However, photographic evidence for Desmodus in 
flight indicates that there is relatively little variability in the plane 
through which the wing is adducted. The heavy wing loading in 
this species (Hartman, 1963), combined with the proportionally 
large meals that are consumed (Wimsatt, 1969), seem to have re- 
sulted in relatively unvarying wingbeat patterns as opposed to hov- 
ering, nectar-feeding species such as Leptonycteris sanborni (Alten- 
bach, 1968). 

Along with the M. serratus anterior, posterior division, the sternal 
M. pectoralis adducts the humerus during the powered phase of 
the jump. It is doubtful that the angle of the jump is controlled by 
the M. pectoralis, as a jump, particularly when the bat has a full 
stomach of blood, probably requires contraction of the entire mus- 
cle. Variation in the rotation of the humerus during the jump is 
likely under the control of the M. subscapularis, suprascapular 
group, deltoid group, clavicular M. pectoralis, and M. latissimus 
dorsi. 

During the wingbeat cycle, the strong pronation of the arm and 
hand, which orients the wing into a thrusting configuration during 
the first half of the downstroke, is a result of contraction of the 



102 Spec. Publ. Amer. Soc. Mamm. 6 

Sternal division of M. pectoralis. There is perhaps more variability 
in the function of this muscle during a wingbeat cycle than in a 
jump. Greater contraction of specific parts of the muscle mass can 
vary the degree of pronation and the plane of adduction of the 
wing. As in a jump, the rotational stability is also controlled by the 
supraspinatus, infraspinatus, subscapularis, deltoid group, clavic- 
ular M. pectoralis, and M. latissimus dorsi. 

In terrestrial locomotion, the sternal M. pectoralis probably sup- 
ports most of the weight directed against the pectoral limbs. When 
the bat is in elevated walking postures or standing in terrestrial 
feeding posture with much of the weight probably supported by 
the clavicle and posterior division of the M. serratus anterior, moving 
the brachium is the task of the clavicular M. pectoralis, deltoid 
group, and M. latissimus dorsi. Sudden movements from these pos- 
tures would seemingly require the power of the sternal M. pecto- 
ralis. 

M. pectoralis abdominalis (Fig. 44). — Origin is on the abdominal 
fascia beginning 2.5 mm lateral to the midline at the level of the 
posterior tip of the xiphoid process and extending posterolaterad 
for roughly 9 mm. Insertion is by a flat tendon, which attaches to 
the medial 2 mm of the ventral aspect of the pectoral ridge pos- 
terior to the insertion of the M. pectoralis. 

As in other species, the M. pectoralis abdominalis is a rotator (pro- 
nator) and flexor of the humerus. During the downstroke it can 
increase pronation to form more of the medial wing into a thrust- 
ing attitude or can oppose the supinating force exerted by the M. 
biceps brachii. The pronation during the flick phase is probably 
aided by this muscle along with the M. latissimus dorsi and M. teres 
major. 

In terrestrial locomotion, the power stroke of the pectoral limb 
is probably aided by this muscle as it pronates and flexes the hu- 
merus. The forearm is forced downward and posteriad by this 
movement, thus driving the body forward. 

Flexor Group of the Arm 

M. coracobrachialis (Fig. 45). — Origin is on the dorsal third of the 
anterior face of the coracoid process. Insertion is over about 4 mm 
of the anteroventral surface of the humerus beginning approxi- 
mately 1 1 mm lateral to the medial end of the pectoral ridge. 



^^^J^J^ 



Altenbach — Vampire Locomotor Morphology 103 



K y L M 







L 




-•JY«V**V1, r- 



I I I I I I I I I I 1 1 I I I I I I I I I I I 

A BCDE FGH I J KLMNOPQRSTUV 

Fig. 40. Electromyogram of right M. biceps brachii, coracoid head, of Desmodus 
and corresponding locomotor behavior. The contraction of the muscle occurs 
slightly after the electrical event and is shown as a solid line above the electromy- 
ographic recording. Corresponding locomotor stages and portions of the electro- 
myogram are indicated by the same letters. 

The M. coracobrachialis is a rather weak adductor and extensor 
of the humerus. It probably aids in adduction of the wing and 
exerts a stabilizing force to the brachium. 

M. biceps brachii (Figs. 42, 44-47). — The origin of the coracoid 



104 Spec. Publ. Amer. Soc. Mamm. 6 

head is on the posterior and lateral aspect of the ventral three- 
fourths of the tip of the coracoid process. The origin of the glenoid 
head is by a tough tendon from the tubercle a millimeter anterior 
to the glenoid fossa on the lateral aspect of the base of the coracoid 
process. Insertion is by a heavy tendon that runs over the ridge on 
the proximal end of the radius and attaches into the flexor fossa 
on the posterior side of the radius. 

As in other bats (Vaughan, 1959; Norberg, 19706), the bellies of 
the biceps are flexors of the forearm and, because of the articu- 
lation of the radius and humerus that allows only flexion and ex- 
tension, supinators of the arm. Electromyographic data from a 
jump into flight were recorded from electrodes in the coracoid 
head, but probably are representative of the function of both 
heads. There is little or no activity during the powered phase of 
the jump (Fig. 40D-G) and the first contraction is a short burst 
during the initial part of the coasting phase, which flexes the fore- 
arm (Fig. 40G-H). Contraction again begins at the first of the 
downstroke and continues until the beginning of the flick phase 
of the upstroke (Fig. 40K-N). When opposed by contraction of the 
M. triceps brachii, the biceps causes adduction of the arm and, as 
Vaughan (1959) pointed out, provides rotational stability as it op- 
poses the pronating forces applied by the M. pectoralis. When the 
M. triceps brachii ceases contraction in the last half of the down- 
stroke (Fig. 38), the biceps flexes and supinates the arm (Fig. 40L- 
N). The function is similar in the next two cycles (Fig. 40O-V). 

M. brachialis (Figs. 46-47). — Origin is over about 9 mm of the 
anterior face of the humerus beginning 12 mm lateral to the distal 
end of the pectoral ridge. Insertion is into the flexor fossa of the 
radius in common with the tendon of the M. biceps brachii. This 
muscle probably assists in the flexion and stabilization of the fore- 
arm, as suggested in other species of bats (Vaughan, 1959, 1970c; 
Norberg, 19706). No electromyographic data are available. 

Flexor Group of the Forearm 

M. flexor carpi ulnaris (Figs. 47, 49). — Origin is on the ventral 
aspect of the ulna from its medial tip laterally for 5 mm and on 
the adjacent M. palmaris longus about 4 mm distal to its origin. 
Insertion is onto the posteromedial surface of the pisiform a third 
of the distance to its ventral tip. 



Altenbach — Vampire Locomotor Morphology 105 

As in several other species of bats (Vaughan, 1959), this is a 
flexor of the fifth metacarpal and thus the hand, because forces 
applied to the pisiform are transmitted to the fifth metacarpal. 
However, the belly is relatively small and the tendon is extremely 
thin, indicating that the duty of flexion of the fifth metacarpal has 
been taken over by other muscles such as the M. extensor carpi 
ulnaris. As in Macrotus (Vaughan, 1959), the origin allows complete 
independence of movement at the elbow and facilitates the ab- 
duction of the extended hand-wing anterior to the body to provide 
low drag on the upstroke. 

M. palmaris longus (Figs. 47, 49). — Origin is by a heavy tendon 
on the distal tip of the spinous process of the ventral (medial) 
epicondyle of the humerus and from the ventral side of the prox- 
imal 6 mm of the M. flexor digitorum profundus. Insertion is by an 
aponeurosis onto the basal and distal thumb pads, on the ventral 
sesamoids at the first metacarpophalangeal junction, on the ante- 
rior face of metacarpal II, about 13 mm distal to its base, and on 
the ventral aspect of the proximal few millimeters of metacarpals 
III and V. 

The relatively heavy attachments on the first digit and the rather 
large belly of the palmaris longus in Desmodus suggest that this 
muscle is important in ventral flexion of the thumb during the 
jump and perhaps in terrestrial locomotion. The attachments on 
the second and third metacarpals are suited to flex them toward 
the radius and probably aid the M. flexor carpi radialis, M. flexor 
carpi ulnaris, and M. extensor carpi ulnaris in keeping the wing tightly 
folded during the jump and in terrestrial locomotion. When the 
hand is fully extended in flight, the radial extensors of the hand 
easily overpower this muscle, but it can function to ventrally brace 
the second and third metacarpals against the force of the air stream 
and help strengthen the leading edge of the wing. The attachment 
to the fifth metacarpal probably serves a relatively passive bracing 
function, as it is not suited to flex the metacarpal toward the radius. 

The electromyographic data for the palmaris longus are not 
ideal, because the bat did not fully extend the left wing during 
most of the flight. However, the recorded activity of the muscle is 
probably similar to that in normal locomotor activity. Sporadic con- 
traction occurs during the step and partial hop before the bat 
jumps into flight (Fig. 41A-G) and during the powered phase of 
the jump (Fig. 41H-I). The flick phase does not seem typical (par- 



106 Spec. Publ. Amer. Soc. Mamm. 6 



B 



fX? 



^4#^ ^^ w^// 



H 



C D E 




'4A. 



F 




%? 





I I I I 

Q R S T 



Fig. 41. Electromyogram of right M. palmaris longus of Desmodus and corre- 
sponding locomotor behavior. The contraction of the muscle occurs slightly after 
the electrical event and is shown as a solid line above the electromyographic re- 
cording. Corresponding locomotor stages and portions of the electromyogram are 
indicated by the same letters. 



Altenbach — Vampire Locomotor Morphology 107 




clavotrapezius 
occipito-pollicalis 
omocervicalis 
acromiotrapezius 
spinodeltoideus 
acromiodeltoideus 
clavodeltoideus 
triceps lateralis 
triceps longus 

teres major 
latissimus dors 
biceps brachii 

spinotrapezius 



rhomboideus 
levator scapulae 
serratus anterior, ant. div. 

acromion proc. 
supraspinatus 

nfraspinatus 

edial scapular 
border 

spinodeltoideus 
serratus anterior, 
post. div. 

spinotrap. (cut) 

lat. dor. (cut) 



Fig. 42. Dorsal view of pectoral girdle musculature of Desmodus. Superficial 
muscles (left of midline) and view with M. acromiotrapezius, M. spinotrapezius, M. 
latissimus dorsi, and M. acromiodeltoideus removed (right of midline). 



ticularly the movements of the right wing with the implanted elec- 
trodes), but contraction occurs through this phase, perhaps to "fa- 
vor" the wing and keep it partially flexed (Fig. 41L-N). Contraction 
again occurs in the first half of the downstroke and ceases until the 
middle of the upstroke, when a short burst occurs, perhaps to 
partially flex the digits and "cock" them for extension in the flick 
phase (Fig. 410-S). The contraction at the beginning of the flick 
phase may be to resist the radial extensors and let their contraction 
build up maximal tension before relaxation of the palmaris, and 
perhaps other flexors, suddenly releases the hand. This could con- 
tribute to a "snap" of the chiropatagium to provide considerable 
thrust. The wing is more extended at this point and contraction 
occurs during the entire downstroke. 

M. flexor carpi radialis (Figs. 47, 49). — Origin is on the postero- 
ventral aspect of the proximal half of the belly of the M. pronator 
teres. Insertion is on a large tubercle on the anteroventral base of 
metacarpal II. 

In phyllostomatids such as Macrotus, the insertion of this muscle 



108 Spec. Publ. Amer. Soc. Mamm. 6 



scapula 



ledial head 




triceps brachii 

lateral head . 
medial head 
long head — 




Fig. 43. 
removed. 



Ventral view of M. triceps brachii oi Desmodus: A, intact; B, medial head 



is on the third metacarpal (Vaughan, 1959). The insertion on 
metacarpal II in Desmodus permits the leading edge of the wing to 
be actively flexed against the radius rather than passively flexed by 
flexors of the third, fourth, or fifth digits. The position of the 
insertion also reflects the need to rapidly fold the wing in an alight- 
ing maneuver and to hold it firmly folded during terrestrial lo- 
comotion, climbing, and jumping. 

M. pronator teres (Fig. 47). — Origin is on the tip of the spinous 
process of the ventral (medial) epicondyle of the humerus. Inser- 
tion is on 10 mm of the ventral aspect of the radius beginning 8 
mm distal to the tip of the spinous process. 

As the humero-radial articulation allows little but flexion and 
extension, this muscle acts as a weak flexor and a powerful ventral 
brace of the radius. In terrestrial locomotion or alighting maneu- 
vers, forces against the carpus are transferred to the humerus as 
a strong supinating torque. The elbow must be strongly braced 
against these forces without excessive connective tissue binding 
that would reduce mobility. Co-contraction of the M. supinator also 
stabilizes the radius against the humerus. 

M. flexor digitorum profundus (Figs. 47, 49). — The origin includes 
the ulna from 5 mm of its interosseus and ventral surface distal to 



Altenbach — Vampire Locomotor Morphology 109 

its contact with the radius; the tip of the spinous process of the 
humerus; and a few fibers from the posterior surface of the radius 
5 mm distal to the spinous process of the humerus. Insertion is as 
follows: the tendon divides at the carpus into 1) a heavy tendon 
that inserts on the middle of the ventral aspect of the first phalanx 
of digit I (a tiny tendon diverges from this tendon and is the origin 
for a small muscle inserting on the anterolateral aspect of the distal 
tip of metacarpal I); 2) a tendon that runs over the pisiform and 
inserts on the proximoventral tips of the first and second phalanges 
of digit III; and 3) a tendon of origin for one belly on the M. 
interossei that inserts on the posterior surface of metacarpal III, 10 
mm distal to its proximal base. 

This rather massive muscle supplies most of the ventral flexive 
force to the thumb as it provides the last upward thrust in the 
powered phase of the jump. The attachments to the metacarpal 
and the two proximal phalanges of digit III flex the third digit 
and help keep the wing tightly folded during the jump and in 
terrestrial locomotion. Also, all of the forearm flexors of the 
thumb, the M. flexor digitorum profundus, M. palmaris longus, and 
the M. abductor pollicis longus have flexive attachments to at least 
one of the other digits and help keep the chiropatagium folded 
against the radius during ventral flexion of the thumb. 

In flight, contraction of the flexor digitorum profundus would 
ventrally brace the metacarpal and phalanges of the third digit and 
could control depression of much of the leading edge of the wing 
and the degree of upward deflection of the phalanges of digit III 
by opposing the upward force of the air. 

Extensors of the Manus 

M. interosseus dorsale (Figs. 48-49). — Origin is on the posteroven- 
tral surface of the base of metacarpal II. Insertion is by an apo- 
neurosis on the antero ventral aspect of the tip of metacarpal III 
and on the proximal half of the anteroventral surface of the first 
phalanx of digit III. 

It seems odd that this muscle should be absent in Macrotus and 
Myotis (Vaughan, 1959) and present in Eumops (Vaughan, 1959), 
Plecotus auritus (Norberg, 19706), and Desmodus. In Desmodus it 
pulls the first phalanx of digit III anteroventrad and tightens the 
chiropatagium between digits III and IV. It also braces the first 



110 spec. Publ. Amer. Soc. Mamm. 6 



occipito-pollicalis. 



clavodeltoideus. 



sternal pectoralis 



biceps brachii 

coracoid head 

glenoid head 

coraco-cutaneus 

pectoralis abdom 




clavicular pectoralis 

subclavius 

coracoid process 

pectoral ridge 
biceps brach. 
coracoid head 
glenoid head 
serratus ant. 
posterior div. 



pect. abdom. 



Fig. 44. Ventral view of pectoral girdle musculature of Desmodus. Superficial 
muscles (left of midline) and view with M. pectoralis, sternal division, and M. clav- 
odeltoideus removed (right of midline). 



phalanx of digit III against upward deflection, and limits upward 
deflection to phalanges two and three. 

Flexor Group of the Manus 

M. abductor pollicis brevis (Fig. 49). — See the account of M. ab- 
ductor pollicis longus. 

M. flexor pollicis brevis (Fig. 49). — Origin is by a long tendon from 
the anteroventral tip of the lunar and from the ligament between 
the anterolateral tip of the trapezium and the anterior base of 
metacarpal II. Insertion is on the medial aspect of the distal tip of 
metacarpal I and on the lateral aspect of the distal tip of metacar- 
pal I. 

The two bellies of this muscle are ventral flexors of metacarpal 
I if contracting simultaneously and, if contracting singly, are ven- 
trolateral or ventromedial flexors of the first metacarpal. As pow- 
erful ventral flexion of the thumb is the function of the M. flexor 
digitorum profundus, M. palmaris longus, and M. abductor pollicis lon- 
gus, the flexor pollicis brevis probably is more important in moving 



Altenbach — Vampire Locomotor Morphology 1 1 1 



clavicle 
subclavius 
coracoid process 
lesser tuberosity 



serratus ant., ant.div. 
subscapularis 



biceps brachii 
coracoid head 



serratus ant. 
post. div. 




tendon of orig. for 

glenoid biceps brach. 

pectoral ridge 

coracobrachialis 

biceps brach 
glenoid head 



Fig. 45. Ventral view of deep pectoral girdle musculature of Desmodus. View 
(left side) with M. pectoralis, sternal division, M. clavodeltoideus, M. pectoralis abdom- 
inalis, M. pectoralis, clavicular division, removed and view (right side) with the above- 
mentioned muscles and the M. subclavius and M. biceps brachii, coracoid head, re- 
moved. 



the thumb in delicate maneuvers during terrestrial locomotion or 
climbing. In elevated walking or in a terrestrial feeding posture, 
this muscle helps shift the weight from the basal pad of the thumb 
to the distal pad at the metacarpophalangeal junction (Fig. 2C). 
When the bat feeds from the neck or head of an animal, the 
thumbs must be moved occasionally to give the claws purchase on 
the skin or hair, and these muscles probably function in such move- 
ments. 

M. adductor pollicis (Figs. 48-49). — Origin is on the anteroventral 
aspect of metacarpal II, 1.5 mm distal to the insertion of the M. 
flexor carpi radialis and on the ventral aspect of metacarpal III distal 
to its articulation with the carpus. Insertion is by an aponeurosis 
on the dorsolateral aspect of the distal tip of metacarpal I and by 
a tendon on the dorsal base of the second phalanx of digit I. 

The more delicate ventrolateral movements of the thumb during 
terrestrial locomotion, climbing, and perhaps feeding are powered 
by this muscle and the lateral belly of the M. flexor pollicis brevis. If 
the first metacarpal is braced by both bellies of the latter muscle, 



112 Spec. Publ. Amer. Soc. Mamm. 6 



propatagjalis proprius 




e. d. q. p. 



Fig. 46. Dorsal view of superficial musculature of the right forearm of Desmodus. 
Abbreviations: e.c.r.b. , M. extensor carpi radialis brevis ; e.c.r.l., M. extensor carpi radialis 
longus; sup., M. supinator; e.d.c, M. extensor digitorum communis; e.c.u., M. extensor 
carpi ulnaris; e.p.b., M. extensor pollicis brevis; e.d.q.p., M. extensor digiti quinti proprius. 



the M. adductor pollicis could elevate the terminal digit and claw, 
and draw the entire digit ventrolaterad. 

M. interossei (Fig. 49). — Individual muscles of this group are as 
follows: 

1) Origin is by a tendon on the ventral tip of the trapezium. 
Insertion is on the posterior half of the ventral base of phalanx 
one, digit III. 

Along with the M. interosseus dorsale, this muscle stabilizes the 
first phalanx of digit III against deflection upward by the force of 
the air stream during adduction of the wing. 

2) Origin is from the magnum and a tendon from the ventro- 
lateral aspect of the base of metacarpal IV. Insertion is on the 
ventrolateral aspect of the tip of metacarpal IV and on the ven- 
trolateral aspect of the proximal tip of phalanx one. 

This is a weak flexor of the first phalanx of digit IV and serves, 
along with the third belly of this group of muscles, to brace the 



Altenbach — Vampire Locomotor Morphology 1 13 




f. d. p. 



Fig. 47. Ventral view of superficial musculature of the right forearm of Des- 
modus. Abbreviations: f.c.r., M. flexor carpi radialis; e.c.r.l., M. extensor carpi radialis 
longus; p.t., M. pronator teres; f.d.p., M. flexor digitorum profundus; p.l., M. palmaris 
longus; e.c.u., M. extensor carpi ulnaris; f.c.u., M. flexor carpi ulnaris. 



fourth metacarpal against upward deflection during adduction of 
the wing. It also assists in flexing the phalanges as the wing is 
folded during an alighting maneuver or for terrestrial locomotion. 

3) Origin is from the magnum and a small tendon from the 
ventromedial aspect of the proximal base of metacarpal IV. Inser- 
tion is on the ventral base of the first phalanx of digit IV by a 
tendon. 

This muscle works along with the second belly of this group, 
and its function is essentially identical. 

4) Origin is from a slip of the tendon of the M. flexor digitorum 
profundus. Insertion is on the posteromedial surface of metacarpal 
III 10 mm distad to its proximal tip. 

When the M. flexor digitorum profundus contracts to ventrally flex 
the thumb during a jump or in terrestrial locomotion, the origin 
of this muscle is stretched, and the force, transmitted through the 
belly, flexes the third digit against the radius. Contraction of this 
belly of the M. interosseus under these conditions applies more force 



114 Spec. Publ. Amer. Soc. Mamm. 6 



e.c.r. I 




Fig. 48. Dorsal view of the musculature and tendons of the right carpus of 
Desmodus. All of the M. extensor indicis, except its major insertional tendon, is re- 
moved. Abbreviations: e.c.r.l., M. extensor carpi radialis longus; e.c.r.b., M. extensor 
carpi radialis brevis; e.i., M. extensor indicis (major tendon); e.p.b., M. extensor pollicis 
brevis; e.c.u., M. extensor carpi ulnaris; e.d.q.p., M. extensor digiti quinti proprius; e.d.c, 
M. extensor digitorum communis; i.d., M. interosseus dorsale; add. poll., M. adductor 
pollicis; I-V, metacarpals I-V; 1, 2, phalanges of digit I. 



and holds the third digit against the radius more firmly. When the 
wing is extended during the wingbeat cycle, the elastic properties 
of this muscle allow contraction of the M. flexor digitorum profundus 
to ventrally brace the third metacarpal and first phalanx of digit 
III but only apply minimal flexive force. 

M. abductor digiti quinti (Fig. 49). — Origin is by a tendon from 
the posterior tip of the scaphoid. Insertion is by a broad aponeu- 
rosis on the ventromedial aspect of the distal tip of metacarpal V 
and on the ventromedial base of phalanx one. 

This muscle is large in Desmodus and is situated to brace the fifth 
metacarpal against the force of the airstream during adduction of 
the wing and ventrally flex the first phalanx of digit V. In Macrotus 
(Vaughan, 1959), this muscle is quite tendinous and acts as an 
inelastic brace; however, the relatively large, fleshy belly suggests 
its function is more variable in Desmodus. Relaxation during the 
first half of the downstroke allows the upward deflection of the 
phalanges (Fig. 19), which provides thrust from the middle of the 
wing. Contraction ventrally flexes the phalanges and shapes this 



Altenbach — Vampire Locomotor Morphology 1 15 



palm. long. 




Fig. 49. Ventral view of the musculature and tendons of the right carpus of 
Desmodus: A, view of the insertion of the M. palmaris longus; B, view of the anatomy 
with the palmaris removed. Abbreviations: f.c.u., M. flexor carpi ulnaris; abd. p.l., 
M. abductor pollicis longus (and perhaps brevis); int. (1-4), bellies of Mm. interossei; 
f.c.r., M. flexor carpi radialis; f.p.b., M. flexor pollicis brevis; f.d.p, M. flexor digitorum 
profundus; add. poll., M. adductor pollicis; abd. d.q., M. abductor digiti quinti; o.d.q., 
M. opponens digiti quinti; e.c.u., M. extensor carpi ulnaris; II-V, metacarpals of digits 
II-V (metacarpal I not visible); 1, 2, phalanges of digit I. 



part of the wing into a cambered surface suited for production of 
lift. This function is probably aided by contraction of the M. ab- 
ductor pollicis longus, which displaces the origin proximally. 

M. opponens digiti quinti (Fig. 49). — Origin is by a tendon on a 
tubercle of the posteroventral aspect of the pisiform adjacent to its 
articulation with metacarpal V. Insertion is by an aponeurosis on 
the ventrolateral aspect of the tip of metacarpal V. 

The tendons of this muscle and the M. abductor digiti quinti fuse 
distally, thus their function is essentially the same. However, be- 
cause the opponens digiti quinti originates on the pisiform, it is 
not affected by contraction of the M. abductor pollicis longus and 
can flex the phalanges of the fifth digit, even if the abductor is 
relaxed. Co-contraction of all three can powerfully flex the pha- 
langes and overpower the M. extensor digiti quinti proprius to hold 
the fifth digit at a high and rigid camber. 



DISCUSSION 



Terrestrial Locomotor Behavior 

j-^ESMODUS rotundus is the most terrestrially oriented of bats; its 
-Ly agility in quadrupedal locomotion far surpasses that of other 
species and even that of many small rodents and carnivores. As 
several authors have described (Beebe, 1927; Price, 1950; Ditmars 
and Greenhall, 1935, 1936; Dalquest, 1955; Wimsatt, 1959), it runs 
along horizontal or vertical surfaces with ease and executes sudden 
evasive maneuvers that make it difficult to capture. This terrestrial 
facility is closely involved with feeding behavior, as no other bat 
except Desmodus (and perhaps the other sanguivorous bats, Diaemus 
and Diphylla) shows such agility in terrestrial locomotion. Obser- 
vations of Desmodus scrambling over the backs and necks of host 
animals prior to feeding (or to avoid movements of the host animal 
to brush them off), and running or hopping about on the ground 
while feeding, illustrate the adaptive value of this effective terres- 
trial locomotion. Although several other species of bats easily move 
about on the ground and occasionally catch food to alight prior to 
catching the food, Desmodus, and perhaps to a lesser extent the 
other two sanguivorous bats, are the only chiropterans that have 
become so specialized in feeding as quadrupeds. 

According to Vaughan (1959, 1970^, 1970^), bats probably 
evolved as crevice dwellers and thus, initially, were adapted for 
terrestrial locomotion in confined spaces. Even in bats such as Eu- 
mops perotis, Myotis velifer (Vaughan, 1959), Antrozous pallidus (Burt, 
1934), Nyctalus noctula (Anonymous, 1969), Rhinolophus ferrume- 
quinum (Southern, 1964), and Eptesicus fuscus (Altenbach, 1968), 
which readily move about in quadrupedal fashion on the ground 
or other surfaces, the limbs are directed more or less lateral to the 
body, which is typically held quite close to the surface. The power 
strokes are directed posterolaterally by flexion and slight pronation 
of the brachii, extension of the elbows, and by posterior swings of 
the laterally extended pelvic limbs. These types of movements are 
necessary in a crevice or in confined roosts, but are inefficient, 
inasmuch as the weight is supported on laterally directed limbs. 
The large M. pectoralis is well suited to support much of the weight, 

116 



Altenbach — Vampire Locomotor Morphology 1 17 

but the muscles that move the limbs have to work against the forces 
that maintain posture. 

As described in the section on locomotion, Desmodus inclines the 
body and holds it well above a horizontal surface when walking or 
running. The shanks are directed almost vertically, the brachii are 
directed relatively posterolaterally, and the forearms are partially 
flexed and directed anteroventrally and slightly laterally. The net 
result of this posture is that the contact of the limbs with the surface 
is shifted nearer the body and more below it, requiring less effort 
to maintain the posture. Thus greater muscular effort can be de- 
voted to moving the limbs, resulting in more rapid and complex 
movements. Posteroventral thrusts with both pectoral and pelvic 
limbs produce a hopping gait that rapidly carries the bat over the 
ground and allows chasing of host animals. 

The orientation of the hind limbs makes them well suited to 
pulling, thus the bats typically climb backwards. The pectoral limbs 
incline the body away from the surface and aid climbing by for- 
ward thrusts. With the body in a climbing position, the pectoral 
limbs are able to thrust the bat outward into flight or laterally in 
an avoidance reaction. There are few records of predators feeding 
upon bats in roosts, thus the agility on vertical surfaces in roosts 
appears to be a secondary advantage of locomotor mechanisms 
evolved for terrestrial feeding. 

Desmodus regularly consumes a large volume of blood, often as 
much as 100 per cent of its body weight, in a single feeding period 
(Wimsatt, 1969). This, and the habit of feeding from the ground 
or moving about on the ground between feeding periods, require 
the ability to launch into flight from the ground when heavily 
loaded. Host species, such as large ungulates, often are found in 
the open and some distance from trees or rock outcrops on which 
the bats could climb and from which they could drop into flight. 
Many other species of bats require a drop from a roost to build 
the air speed necessary for flight. Bats other than Desmodus that 
can fly from the ground, such as some nectar feeding species {Lep- 
tonycteris, Glossophaga) and lightly-loaded insectivorous taxa {Antro- 
zous, Myotis, Plecotus), push off from the surface with partially or 
fully extended wings and begin flight with a lift-generating wing- 
beat cycle. 

The ability to shift the pectoral limbs almost directly under the 



118 Spec. Publ. Amer. Soc. Mamm. 6 

body and several other anatomical modifications allow Desmodus to 
achieve flight from the ground by a powerful jump, which carries 
it, even when fully gorged on blood, high enough above the surface 
to initiate a high-amplitude wingbeat cycle. The jump is effected 
by a powerful adduction of the brachii, extension of the elbows, 
and ventral flexion of the thumbs. The extreme elongation of the 
thumbs, which are proportionally longer than in any other bat, 
provides a long lever arm for this flexive movement that adds the 
final upward momentum during the jump. The pelvic limbs supply 
little of the upward thrust, as they function primarily to shift the 
center of gravity over the powerful pectoral limbs. The jumping 
behavior also plays an important role in avoiding being stepped on 
by a large host animal and perhaps avoiding terrestrial predators. 
Although jumps into flight are directed primarily forward and 
upward, a direction that allows maximal thrust from the pectoral 
limbs, avoidance jumps can occur in any direction. Both avoidance 
jumps and jumps into flight are powered by the pectoral limbs, 
while the hind limbs shift the weight into the line of the jump. 

Alighting maneuvers on a horizontal surface are essentially the 
reverse of the movements used in a jump into flight. Contact with 
the substrate is made first with the thumbs. The downward mo- 
mentum is slowed by muscular resistance to hyperextension of the 
thumbs, flexion of the elbows, and abduction of the brachii. The 
movement effectively breaks the force of the landing and is prob- 
ably advantageous for alighting softly on or near a host animal. 
Rodney Honeycutt, Ira Greenbaum, and Robert Baker (personal 
communication) speculate that because obligate blood feeding ap- 
pears in mammals only in the genera Desmodus, Diphylla, and Diae- 
mus, these bats probably evolved from a common ancestor that was 
already a sanguivore. I cannot speculate about the evolutionary 
development of sanguivory in bats, but I feel that Desmodus is cer- 
tainly the most derived, from a locomotor morphological stand- 
point, of the Desmodontinae. The morphological modifications of 
the limbs and girdles reflect selective pressures somewhat different 
than those expected to have acted on a bat that typically parasitizes 
large domestic animals of man. 

The habit of feeding on large ungulates from the ground, and 
the ability to feed from relatively active terrestrial rodents, suggest 
that perhaps the bats initially fed on small terrestrial mammals or 
other vertebrates and that the facility for terrestrial locomotion 



Alteyibach — Vampire Locomotor Morphology 1 19 

developed in response to this mode of feeding. Seemingly, if the 
bats had fed initially on large ungulates, they could have readily 
fed from the back or neck and the ability to run on the ground 
would not have been necessary. With only a small thrust of the 
limbs, the bats could have dropped off the back or neck into flight. 
Thus, the complex energy-demanding jump would not have been 
necessary. Probably the mechanisms of the jump evolved as a 
means to rapidly negotiate rough terrain in pursuit of a small 
mammal or other vertebrate, rather than to avoid movements of 
larger animals. Elongation of the thumbs, no doubt, facilitated 
rapid locomotion and permitted increasingly longer hops. Tran- 
sition from a long hop to flight by initiation of the wingbeat cycle 
does not seem a great step. Once developed, the jumping behavior 
probably allowed larger meals to be taken in a single feeding pe- 
riod and perhaps permitted feeding on the limbs of larger animals, 
as it facilitated avoidance maneuvers. 

Flight and Aerodynamic Considerations 

Investigators of bat locomotor morphology have characterized 
bats as relatively derived or underived on the basis of the degree 
of anatomical and behavioral modification contributing to efficient 
flight. In most species characterized by efficient flight, sometimes 
described as relatively derived, there are anatomical features of 
the pectoral limbs and girdles that automatically move distal parts 
of the wings when more medial parts are moved. These features 
also limit the planes of movement possible for the wings, but per- 
mit great mechanical advantage for muscles to power the move- 
ments and allow concentration of muscle mass nearer the center 
of gravity. Such species can fly rapidly over relatively long distances 
with minimal energy expenditure and are well suited for long feed- 
ing periods in flight or for migration. 

Species with inefficient flight, often characterized as underived, 
are better suited to feeding on nectar or fruits, or feeding and 
maneuvering in a cluttered environment, and necessarily lack the 
anatomical features that restrict planes of movement and provide 
automatic movements of more distal parts of the wings. The great- 
er variability of movements permits slow, intricate, or hovering 
flight or terrestrial locomotion necessary for feeding. 

It is important to note that the morphological features of the 



120 Spec. Publ. Amer. Soc. Mamm. 6 

limb and girdle that permit either highly efficient flight (or flexible, 
relatively inefficient flight) may be equally derived and probably 
reflect considerable evolutionary modification. Desmodus is certain- 
ly an example of a morphologically derived bat that has specialized 
in the tremendous variability and amplitude of movements that 
are necessary for flight, rapid terrestrial locomotion, and also for 
jumping, which effects the transition between flight and terrestrial 
locomotion. 

The momentum imparted by the jump is sufficient to carry the 
body approximately 20 to 30 cm above the ground, giving 
the bat time to unfold and position the wings for the first down- 
stroke. However, both forward and upward velocity rapidly de- 
crease during this coasting phase. Desmodus derives forward thrust 
from unfolding the wings, which is similar to a movement in the 
last half of the upstroke in Desmodus and in certain other phyllo- 
stomatid (Altenbach, 1968), vespertilionid, and rhinolophid bats 
(Eisentraut, 1936), and which Norberg (1970(7) termed the flick 
phase. In this movement the digits and forearm are extended and 
the entire arm is powerfully abducted and pronated. The dorsal 
surface of the wing is directed posteriorly and dorsally against the 
air stream, thus providing a component of forward thrust to rein- 
force the forward momentum of the bat prior to initiation of the 
wingbeat cycle. Several muscles power this flick; thus it can gen- 
erate more thrust than can abduction of the wing alone. 

The wingbeat cycle of Desmodus is peculiar because it shows both 
the high amplitude downstroke typical of many vespertilionid bats 
and the extended wing, low drag upstroke, and flick typical of the 
phyllostomatid nectar-feeders to which Desmodus is closely related 
(Forman et al., 1968). The same morphological features of the 
shoulder girdle that permit the limbs to be directed ventral to the 
body in terrestrial locomotion and in the jump allow a downstroke 
of high amplitude. Although the flick, prior to the first downstroke 
after a jump, supplies some increase in forward speed, the air 
speed and upward velocity are low at the start of the downstroke; 
thus maximal thrust and lift are necessary to initiate forward flight. 
As in other bats (Eisentraut, 1936; Vaughan, 1959, 1970c?; Alten- 
bach, 1968; Norberg, 1970a), the force of the air as the wing is 
adducted deflects the phalanges of digit IV upward, thus making 
the portion of the wing adjacent to digit IV a thrusting surface. 
However, the arm is strongly pronated to orient the leading edge 



Altenbach — Vampire Locomutur Morphology 121 

of the wing well below the trailing edge, forming all but the prox- 
imal third of the plagiopatagium and the chiropatagium, nearly 80 
per cent of the wing area, into a thrusting structure. This contrasts 
sharply with published estimates that only 20 per cent of the wing 
area is configured to provide thrust in other bats. Photographs 
taken several wingbeats after initiation of flight indicate that the 
phalanges of the fifth digit also are deflected upward to increase 
this thrusting effect. The distal portion of the chiropatagium often 
is not fully unfolded during the first, and occasionally the second 
or third, downstroke; yet motion pictures indicate rapid accelera- 
tion during this period. Obviously, thrust is being produced by the 
more medial parts of the wing and not by just the propeller effect 
of the distal chiropatagium as is typically described for bat flight. 
During the downstroke, both the upward and forward velocity of 
the body increases, apparently the result of downward and back- 
ward acceleration of air produced by the adduction of the wings. 
Eisentraut (1936) stated that upward drive is produced by the ad- 
duction of the wings in the downstroke but more recent discussions 
of bat flight (Vaughan, 1959, 1966, 1970^, 1970^) suggest lift is 
only produced by air flow over a cambered surface. In Desmodus, 
as in any bat, the latter is perhaps the case in more rapid forward 
flight. However, at least in Desmodus, much of the lift in the initial 
flight following a jump and in the slow accelerating flight that 
follows, is the result of acceleration of air ventrally during adduc- 
tion of the wings. 

An upward deflection of the distal two phalanges of digit III 
during the downstroke perhaps reduces the formation of tip vor- 
tices and, during the last half of the stroke, provides additional 
lift. Adduction of the wings continues slightly anteriorly in the last 
half of the downstroke and the tips occasionally meet below the 
body. The high amplitude of the stroke permits production of 
continuous air acceleration and thus thrust and lift production for 
a relatively long period. 

As in some nectar-feeding species of phyllostomatids, the down- 
stroke gives way to the upstroke by a gradual change of direction 
and position of the wing. Drag is minimized by raising the wings 
anterior to the body, while they are fully extended, and with the 
plane oriented vertically. A pronounced flick, similar to that de- 
scribed by Eisentraut (1936) and Norberg (1970a) in other species, 
completes the upstroke and provides additional thrust. The flick 



122 Spec. Publ. Amer. Soc. Mamm. 6 

can occur only in bats with great freedom of movement of the arm 
and hand. In species that have evolved more efficient, high-speed 
flight, anatomical modifications of the pectoral limb allow more 
automatic extension and flexion of the hand and centralization of 
weight and do not permit this type of upstroke and flick. There 
is little doubt that this movement produces forward thrust in Des- 
modus, as Eisentraut (1936) believed it does in several other species. 
The most conclusive evidence is the rapid acceleration during this 
movement prior to the first upstroke following a jump. Although 
of greater amplitude, the initial flick is similar to that observed in 
subsequent wingbeats of slow forward flight. There is only slight 
flexion of the digits toward the forearm during the first half of the 
upstroke in slow forward flight, thus extension of the digits plays 
a lesser role in flight than it does in the initial flick. 

Although no high-speed photographic data are available on rap- 
id flight, the flick is certainly more important in slow flight than 
in rapid flight. During the flick, thrust is derived by a posterior 
swing of the more distal portions of the wing against the air. Ob- 
viously, as the forward speed of the bat increases, the thrust from 
the flick decreases. The high thrust required during the initial 
flight following a jump is probably not so vital at high cruising 
speeds and the upstroke is basically a recovery stroke. There is 
almost certainly a modification of the wingbeat cycle during rapid 
forward flight, but it remains for high-speed photographs to illus- 
trate it. Perhaps the amplitude of the downstroke is less and the 
stroke begins at a lower angle above horizontal (and continues 
quite deep), as in some molossid bats, which are best suited for this 
type of flight (Vaughan, 1959, 1966, 1970^). Inasmuch as Desmodus 
is anatomically suited for the upstroke with the wing positioned 
anterior to the body and its plane oriented vertically, this portion 
of the stroke may remain relatively unchanged, and a pronounced 
flick may occur. However, it may be more passive than in initial 
flight after a jump or in slow forward flight. 

Desmodus has a heavy wing loading (4.8 cmVg), as do molossids 
such as Molossus bondae (4.0 cmVg), and phyllostomatids such as 
Phyllostomus hastatus (3.4 cm^/g), and Artibeus jamaicensis (4.5 cmV 
g) — Hartman, (1963). However, its aspect ratio is low (2.66) as 
compared to Molossus bondae (3.6) and Phyllostomus hastatus (3.48). 
Struhsaker's data (1966), calculated by slightly different methods, 
place Desmodus (4.9) and Leptonycteris sanborni (4.6) below Molossus 



Altenbach — Vampire Locomotor Morphology 123 

nigricans (5.9) and Tadarida brasiliensis (6.7), and above several 
species varying from 4.13 {Myotis velifer) to 2.44 {Antrozous pallidus) . 

These data illustrate that Desmodus is somewhat unique in having 
both a heavy wing loading and a low aspect ratio. Other investi- 
gators have associated high aspect ratio and high wing loading with 
relatively high-speed, unmaneuverable direct flight, such as that 
of many molossid bats. Many of the species with low aspect ratio 
wings, such as Antrozous pallidus, Myotis lucifugus, and Pipistrellus 
hesperus are lightly loaded and have delicate, even hovering, flight. 
Although Leptonycteris is less heavily loaded than is Desmodus, 
Struhsaker (1961) found its loading more comparable to Desmodus 
than to the other bats he investigated. The flight of these two bats, 
however, is quite different. In slow and hovering flight, Leptonyc- 
teris gains high lift from a medial and anterior swing of the forearm 
and hand produced by a flexion of the elbow in the last half of the 
downstroke (Altenbach, 1968). This movement supplies lift with- 
out movement of the body through the air stream. The length of 
the hand compared to that of the arm is relatively greater in Lep- 
tonycteris than in Desmodus (Findley et al., 1972) and reflects the 
role of the hand in lift production. Desmodus exhibits no such mod- 
ification of the wingbeat cycle, and the relatively shorter and small- 
er hand-wing probably reflects evolutionary compromises for both 
flight and terrestrial locomotion. Desmodus appears to utilize a high 
amplitude downstroke to provide maximal thrust and lift during 
the wingbeat cycles following a jump. As thrust is certainly pro- 
duced during the downstroke by much of the plagiopatagium in 
addition to the chiropatagium, a large chiropatagium is not nec- 
essary for thrust production. Elongation of the wings would be 
disadvantageous, because the jump carries the bat less than 0.3 m 
above the ground and contact of the wings with the ground at the 
bottom of a deep stroke would certainly reduce acceleration. The 
short hand can be folded quickly in an alighting maneuver to pre- 
vent damage to the rather delicate digits and, when folded, is not 
bulky enough to hamper quick movements necessary in the rapid 
terrestrial locomotion typical of this bat. 

The need for a relatively long limb in quadrupedal locomotion 
and particularly for jumping probably prevents reduction in the 
length of the antebrachium and brachium. Thus, to maintain a 
wing of the proportions necessary for production of high thrust 
and lift, and, at the same time to keep its length minimal and 



124 Spec. Publ. Amer. Soc. Mamm. 6 

provide a long limb for quadrupedal locomotion and jumping, the 
relative length of the hand is reduced. 

Since flight serves primarily to move the vampire bat relatively 
short distances between roosting and feeding areas, there is no 
need of anatomical modification for highly efficient flight, typical 
of species that feed in flight or cover long distances in feeding and 
migration. Great freedom of movement of the limbs, however, is 
necessary in the terrestrial feeding behavior of this bat and espe- 
cially for the transition from terrestrial locomotion to flight. Thus 
speciahzation of the appendicular anatomy has been toward ex- 
treme variability and amplitude as well as independence of move- 
ment. Features that allow maximal muscular mass to power high 
energy demanding movements have permitted development of 
jumping behavior for transition between terrestrial and aerial 
modes of locomotion. Some of these same features also permit 
extremely high thrust and lift production necessary to sustain 
flight after a jump and while carrying a heavy load of blood. 

In effect, Desmodus has specialized in variability to feed as a ter- 
restrial vertebrate and yet retain the advantages of a flying verte- 
brate. Thus, this bat has reduced competition with other bats for 
food resources, yet has retained the advantage of mobility and 
ability to use secluded roosts that are inaccessible to most preda- 
tors. 

Anatomical Considerations 

Perhaps the most striking osteological feature of the pectoral 
girdle is the nature of articulation of the clavicle and scapula, which 
allows the scapula to rock freely about its long axis. In other species 
of bats such as Plecotus auritus (Norberg, 1970^), Eumops perotis and 
Myotis velifer (Vaughan, 1959), and Eptesicus fuscus (Altenbach, 
1968), the clavicle is boiind distally to both the acromion process 
and the base of the coracoid process. This feature stabilizes the 
pectoral girdle and gives the muscles that rock the scapula and the 
wing, when the humerus and scapula are locked dorsally or ven- 
trally, great mechanical advantage. However, the amplitude and 
variability of movements of the wing are greatly restricted. Thus, 
efficiency is gained at the expense of flexibility of movement. In 
phyllostomatids such as Leptonycteris sanborni (Altenbach, 1968) and 
Macrotus luaterhousii (Vaughan, 1959), the articulation of the scap- 



Altenbach — Vampire Locomotor Morphology 125 

ula and clavicle is similar to that of Desmodus, but the arrangement 
in Desmodus allows much greater freedom of movement. 

The relatively small angle through which the humerus can be 
adducted or abducted relative to the scapula is surprising, consid- 
ering the great amplitude of the movement of the brachium during 
terrestrial locomotion, jumping, and flight, but suggests that some 
of the muscles that insert on the scapula (M. serratus anterior, tra- 
pezius group, and M. rhomb oideus) are important in moving the 
arm. The spinous process of the ventral (median) epicondyle of 
the humerus has no distal projection typical of many fast-flying 
molossid, vespertilionid, and mormoopid bats; thus, muscles orig- 
inating from it are not affected by movements at the elbow. 

The ulna is strongly fused to the radius distally and rigidly ar- 
ticulated with it proximally. The elevated carriage of the body in 
terrestrial locomotion and jumping in this bat directs forces against 
the long axis of the forearm, thus bracing is needed. In addition, 
the relative independence of the hand from movement at the el- 
bow requires more muscle mass in the forearm, and the rigid ulna 
supplies a solid structure for the origin of such muscle. Investment 
of the distal end of the radius with deep grooves and ridges for 
confinement of insertional tendons of forearm muscles reflects the 
large forces involved during terrestrial locomotion and jumping. 

The carpus is not highly specialized except, as in other bats, to 
limit the movements of all but digit I to a single plane, thus bracing 
the hand-wing against the forces of the air stream in flight. How- 
ever, digit I is greatly elongated, almost 30 per cent the length of 
the forearm, and the articulation of the first metacarpal and tra- 
pezium allows considerable freedom of movement. The articula- 
tion is bound by ligaments ventrally and the articular surfaces slope 
away dorsally from the ventral binding, allowing the thumb to be 
oriented laterally when the forearm is directed perpendicularly 
against a surface. The thumb thereby functions in maintaining 
balance when the body is elevated in terrestrial locomotion, and 
can be flexed powerfully from this position to supply the last up- 
ward thrust in a jump and to provide thrust in rapid terrestrial 
lomotion. 

The metacarpophalangeal joints of digits IV and V and the first 
interphalangeal joint of digit III permit considerable upward de- 
flection of the phalangeal elements distal to them, thus enabling 
the posterior part of the chiropatagium and distal part of the pla- 



126 Spec. Publ. Amer. Soc. Mamm. 6 

giopatagium to supply high thrust during the downstroke. This 
appears unique among bats as, in others, only the phalanges of 
digit IV deflect upward to provide the propeller effect described 
by Vaughan (1959) and Eisentraut (1936). 

The myology of the pectoral girdle and limb was described in 
detail earlier and only the outstanding features, unique to Desmo- 
dus, will be discussed here. 

The M. clavotrapezius is large and its complete separation from 
the M. acromiotrapezius and its heavy origin reflect importance in 
bracing and moving the clavicle. In bats that have the clavicle 
bound in two points to the scapula, the division between these 
muscles is obscure and their function nearly identical, inasmuch 
as rotational forces applied to the scapula are transferred directly 
to the clavicle. The antagonist of the M. clavotrapezius, the M. suh- 
clavius, also is large, and together these muscles stabilize the clavicle 
and probably lower and raise it during jumping and flight. The 
remainder of the trapezius group functions much as in other bats 
to stabilize the scapula and rock it about its long axis. 

Electromyographic data indicate the deltoid group, at least the 
acromio- and spinodeltoids, functions to stabilize the dorsal scap- 
ulohumeral articulation during the powered phase of the jump 
and much of the downstroke in forward flight. This indicates, in- 
directly, that the posterior division of the M. serratus anterior aids 
the M. pectoralis in adducting the humerus through nearly the 
entire jump and much of the downstroke. Vaughan (1959) sug- 
gested that in other bats, particularly those having the scapula and 
clavicle bound in two places, the posterior division of the serratus 
only stops the upstroke and initiates the downstroke, the remain- 
der of the downstroke being powered by the M. pectoralis and M. 
subscapularis as they adduct the humerus using the scapula as a 
fulcrum. In Desmodus, the two largest pectoral muscles, the M. 
pectoralis and the posterior division of M. serratus anterior, are pos- 
sibly responsible for nearly all of the brachial adduction in a jump 
and for much of the brachial adduction in flight. 

The M. clavodeltoideus is situated to extend the humerus, and its 
size and complete separation from the clavicular M. pectoralis sug- 
gest importance of this movement, which produces a power stroke 
in backward climbing and in positioning the pectoral limbs for 
alighting on a horizontal surface. 

The pronators of the arm, the M. latissimus dorsi, M. pectoralis 



Altenbach — Vampire Locomotor Morphology 127 

abdominalis, M. teres major, M. subscapularis, and the posteriormost 
fibers of the sternal M. pectoralis play an important role in the flick 
phase of the upstroke. Pronation of the arms after initial abduction 
of the wings in a vertical orientation anterior to the body swings 
the distal half of the wings posteriorly against the air and provides 
forward thrust. Although Eisentraut (1936) described the flick and 
believed it produced thrust in several species of bats, recent in- 
vestigators have implied the entire upstroke is entirely a recovery 
stroke and provides no thrust. Indeed, in the molossids and many 
vespertilionids, particularly those with features that limit freedom 
of movement of the wings and provide highly efficient flight, the 
flick is nearly impossible and the upstroke is a recovery stroke. 
However, in rhinolophids, a few vespertilionids (Eisentraut, 1936; 
Norberg, 1970(7), and many phyllostomatids, including Desmodus, 
the flick is important in providing thrust, as the relatively large 
size of the muscles involved and the good mechanical advantage 
for the movements they power, suggest. In addition to the above- 
mentioned muscles the three heads of the M. triceps brachii extend 
the elbow to aid this movement, and the two largest forearm mus- 
cles, the M. extensor carpi radialis longus and M. extensor carpi radialis 
brevis, along with the M. extensor indicis, powerfully extend the chi- 
ropatagium. The relatively small acromio- and spinodeltoids are 
certainly not large enough to power a thrust-producing upstroke, 
but they are well suited to raise the wing anteriorly to the body by 
supination of the humerus and thus elevate the flexed forearm. 
This type of upstroke seems quite typical of most phyllostomatids, 
rhinolophids, some vespertilionids, and certainly Desmodus. It re- 
duces drag initially and positions the wing for the flick, in contrast 
to the case in the molossids and mormoopids where the upstroke 
is a recovery stroke and the entire movement is essentially wasted 
effort. 

The M. biceps brachii is adapted to provide a strong, supinating 
force to the arm and to flex the forearm as in other species. It 
probably aids somewhat in the downstroke, even though the hu- 
merus is dorsally locked with the scapular border. However, its 
main function is very likely control of rotational stability of the 
arm and flexion of the forearm at the first of the upstroke. 

The importance of the thumb in Desmodus is evidenced by the 
size of the tendons and bellies of the muscles that ventrally flex it. 
The M. flexor digitorum profundus, the M. palmaris longus, and the 



128 Spec. Piibl. Amer. Soc. Mamm. 6 

M. abductor pollicis longus all have large tendons running to the 
ventral aspect of the first digit. In other bats, the M. abductor pollicis 
longus inserts on the scaphoid, and, in at least one species, Plecotus 
auritis, the M. abductor pollicis brevis originates there and inserts on 
the first digit. In Desmodus, the latter muscle has become tendinous 
and originates directly on the tendon of the former, thus permit- 
ting a longer and larger forearm muscle to power the flexion of 
the thumb. The muscles of the hand, M. abductor pollicis and M. 
flexor pollicis brevis, which insert ventrally on the thumb, are well 
suited to move the thumb to give the claw purchase in such ma- 
neuvers as climbing or walking. All of the above-mentioned fore- 
arm flexors of the thumb have at least one flexive attachment to 
digits II through V. Thus, as they flex the thumb in a jump or in 
terrestrial locomotion, they also aid in keeping the digits flexed 
toward the forearm and flex the phalanges. The major flexor of 
the hand wing, the M. extensor carpi ulnaris, inserts on the medial 
base of metacarpal V where it has great mechanical advantage. 
The insertional tendon is massive and suggests the importance of 
this muscle in holding digit V and, because of ligamentous attach- 
ments between the metacarpals of digits III and V, the rest of the 
hand-wing against the forearm, and in rapidly folding the hand- 
wing during an alighting maneuver. The other major flexor of the 
hand, the M. flexor carpi ulnaris, inserts on the pisiform as in other 
species, but is small and probably only weakly assists M. extensor 
carpi ulnaris. M. flexor carpi radialis is best suited to ventrally brace 
the second metacarpal, and thus the leading edge of the hand- 
wing. This is important when the leading edge of the wing is ori- 
ented below the trailing edge for high thrust production in the 
downstroke. 

Because of the capacity for upward deflection of the phalanges 
of digits IV and V and all but the basal phalanx of digit III, and 
the capacity to vary greatly the degree of pronation or supination 
of the arm, Desmodus can vary greatly the angle of attack, camber, 
and degree of thrusting configuration of the wing. M. extensor dig- 
itorum communis is well suited to actively deflect the phalanges of 
digits III and IV, and the M. extensor digiti quinti proprius is suited 
to deflect the phalanges of digit V. The upward deflection of the 
phalanges of digit V is evident only during about the first half of 
the downstroke, whereas that of digits III and IV persists to the 
end of the downstroke. Thus it is critical that there be independent 



Altenhach — Vampire Locomotor Morphology 129 

control of digit V. As M. abductor digiti quinti originates on the 
scaphoid in Desmodus, flexion of the phalanges of digit V is partially 
under control of the M. abductor pollicis longus, which inserts on 
the scaphoid and first digit. Along with the M. opponens digiti quinti, 
these muscles can ventrally flex the phalanges of digit V to elimi- 
nate the thrusting contour of the wing in that region and transform 
it into a more cambered lift-generating surface. During a jump or 
in terrestrial locomotion, the M. abductor pollicis longus can keep 
the phalanges of the fifth digit flexed as it flexes the thumb by 
pulling the origin of the M. abductor digiti quinti. 

The large M. extensor carpi radialis longus and M. extensor carpi 
radialis brevis originate medial to the center of the elbow joint and 
thus are stretched slightly by extension of the elbow. However, 
they are not invested in a tough connective tissue sheath of deep 
fascia, as is the case in many molossids and vespertilionids, and do 
not automatically extend the digits when the elbow is extended. 
When the flexors of the hand-wing relax, particularly if the elbow 
is partially or fully extended, these muscles can powerfully and 
rapidly extend the fingers. 

SUMMARY 

THE mechanisms of terrestrial locomotion, jumping behavior, 
and flight of the common vampire bat, Desmodus rotundus, 
were analyzed with high-speed photographs and electromy- 
ographs, and were correlated with osteological and myological fea- 
tures of the pectoral girdle and limbs. Great freedom of movement 
at the articulation of the scapula and clavicle, and independence 
of movement in the arm and hand, allow the pectoral limbs to be 
positioned below the body for efficient, rapid, and extremely agile 
terrestrial locomotion. These same anatomical modifications, cou- 
pled with specialization at the shoulder joint, enable the two largest 
muscles in the bat, the M. pectoralis and the posterior division of 
the M. serratus anterior, to power a deep adduction of the arms to 
effect a jump into flight. Extreme elongation and development of 
powerful associated flexor musculature permit the thumbs to pro- 
vide an additional upward thrust in the jump. The jump is vital to 
achieve flight after taking a blood meal from a prey animal on the 
ground. The anatomical features of the pectoral girdle and limb 



130 Spec. Piibl. Amer. Soc. Mamm. 6 

that facilitate both the jump and the remarkable terrestrial loco- 
motion are the most spectacular anatomical modifications in this 
bat. They suggest Desmodus became evolutionarily specialized for 
feeding terrestrially from small active prey animals. Feeding from 
the backs or necks of large prey species seemingly would not have 
necessitated the development of such rapid and agile hopping lo- 
comotion. More important is that this manner of feeding would 
not necessitate the extreme modification of the limbs and girdles 
to execute the jump into flight so characteristic of this bat. The 
habit of feeding from backs and necks of the large domestic ani- 
mals of man is probably an opportunistic utilization of a relatively 
new and more abundant food source. 

During the downstroke of the initial flight following a jump, up 
to 80 per cent of the area of the wings is configured to provide 
thrust. The same large muscles of the pectoral girdle that provide 
adductive power in jumping are able to power at least the first half 
of a deep downstroke that initially supplies high thrust and sub- 
sequently supplies both lift and thrust vital to initiation of forward 
flight. The upstrokes in initial flight occur ahead of the body and 
are terminated in a pronounced flick that provides additional 
thrust and positions the wing for a subsequent downstroke. The 
first few wingbeats following a jump into flight illustrate that thrust 
and lift production are the result of the acceleration of air back- 
ward and downward by movement of the wings. The amplitude 
and directionality of the wingbeat, and the velocity and configu- 
ration of the wings during the wingbeat cycle, determine the mag- 
nitude and direction of the air acceleration. Thus a downstroke 
could produce almost pure lift or pure thrust depending upon 
how it was directed and the configuration of the wings. This view 
contrasts with interpretations of bat flight, which suggest that lift 
is produced by differential velocity of airflow over opposite sides 
of the cambered plagiopatagium and that thrust is produced ex- 
clusively by the distal chiropatagium. In many of the flights re- 
corded in this study, the distal part of the chiropatagium, the por- 
tion often said to be the prime producer of thrust, remained folded 
as the bat rapidly accelerated. Thrust was obviously being pro- 
duced by more medial portions of the wing. 

Among many evolutionary compromises seen in the vampire bat 
are the relative shortening of the hand and the retention of a large 
muscle mass distally in the wing to control the hand movements. 



Altenbach — Vampire Locomotor Morphology 131 

A relatively long hand would be advantageous for lift and thrust 
production, but would be difficult to quickly fold and unfold in 
transition to and from terrestrial locomotion, and would be likely 
to strike the ground on a high amplitude downstroke in the initial 
flight following a jump. It also would be advantageous to have 
more muscle mass concentrated near the center of gravity and to 
have movements in the hand more automatic, as in certain other 
bats, but the need for independent movement in the hand has 
necessitated retention of considerable muscle mass distally. The 
tight folding of the digits during extension of the arm during a 
jump, and the extended orientation of the digits as the arm is 
flexed during the first half of the upstroke, are good examples of 
this independence of movement. 



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INDEX 



(page numbers in italic type denote illustrations) 



Aerodynamics {see Locomotion, 

flight) 
Anatomy {see Myology, Osteology) 

Climbing {see Locomotion, climbing) 

Electromyograph 

ofM. acromiodeltoideus, 85,86, 87 
of M. biceps brachii, 103, 104 
of M. clavotrapezius, 76, 78 
of M. extensor carpi radialis longus, 

94, 95 
of M. latissimus dorsi, 82, 83-84 
of M. palmaris longus, 105, 106, 

107 
of M. spinodeltoideus, 87,88, 89 
of M. spinotrapezius, 77, 78-79 
of M. triceps brachii, 91, 92 

Electromyography 

interpretation of, 72, 73 
techniques of, 6, 7-8, 10 

Flight {see Locomotion, flight, initial 
flight) 

Hanging {see Locomotion, hanging) 
Hopping {see Locomotion, hopping) 

Jump {see Locomotion, jump) 

Locomotion 
alighting 

adaptive significance of, 51, 

118 
on horizontal surface, 49, 50, 

51, 118 
on vertical surface, 51-52 
similarity to jump, 51 
climbing 

ascending, i 6, 17, 18, 117 
descending, 18 



flight 

aerodynamics 

aspect ratio, 122-123 
relative hand length, 123 
wing loading, 122 
aerodynamic requirements, 

42-43 
anatomical specialization for, 

124-129 
downstroke, 42, 43, 46, 47, 48, 
49 
lift and thrust generation 

during, 43-44 
wing configuration during, 
42, 43-44, 46-49 
efficiency of, 119-120 
rapid, 122 

upstroke and flick, 44, 45, 46, 
47, 48, 49 

lift and thrust generation 
during, 45-46, 49 
hanging, 11, 12 

transition to flight from, 12, 
29,50 
hopping, 14,75, 17, 117 

evolution of, 119 
initial flight 

acceleration during, 120-121 
aerodynamic requirements of, 

120-121 
anatomical specialization for, 

125-129 
coasting and initial flick 

acceleration during, 33, 121 
duration of movement, 31, 

38 
wing movement during, 31, 
32, 33, 37, 120 
first downstroke, 33-35, 120- 
122 



135 



136 Spec. Publ. Amer. Soc. Mamm. 6 



acceleration during, 35, 

120-121 
lift and thrust generation 
during, 34, 35, 120-121 
flick (see upstroke and flick) 
flight path during, 31 
into steep flight path, 39, 40 
thrust production during, 

120-121 
turn during, 39, 40, 41 
upstroke and flick, 35-39, 
120-122 

acceleration during, 38 
wing configuration during, 
120-121 
jump 

adaptive significance of, 21-22, 

117 
anatomical specialization for, 

58, 59-60, 125-129 
backward, 27, 28 
evolution of, 119 
in other bats, 1 17 
into flight 

anterolaterally, 27 

coasting phase, 20, 21, 22, 

25-26, 118 
from vertical surface, 29, 30 
from walking gait, 29 
prejump posture, 22, 23 
thrusting phase, 20, 21, 22, 

23-25, 118 
variation in, 22-23 
standing, 9, 10-11 
terrestrial {see also climbing, hop- 
ping, walking) 
agility during, 117 
anatomical specialization for, 

58, 59-60, 125-129 
evolution of, 118-119 
in other bats, 1 16 
significance of limb position, 
117 
walking, 12-13, 14, 117 



Myology 
M. abductor digiti quinti, 114, 115 
M. abductor pollicis brevis, 95-97, 

115 
M. abductor pollicis longus, 96-97, 

115 
M. acromiodeltoideus, 85-86, 107 
M. acromiotrapezius, 78, 107 
M. adductor pollicis, 111-112,77-^, 

775 
M. biceps brachii, 103-104, 107, 

110, 111, 112, 113 
M. brachialis, 104, 772, 775 
M. clavotrapezius, 75-78, 707 
M. clavodeltoideus, 84-85, 107, 

110 
M. coracobrachialis, 102-103, 77 7 
M. coraco-cutaneous, 75, 110 
M. extensor carpi radialis brevis, 93, 

772, 77^ 
M. extensor carpi radialis longus, 

93, 95,112, 113, 114 
M. extensor carpi ulnaris, 98-99, 

772, 775, 77-^, 775 
M. extensor digitorum communis, 

97-98, 772, 77^ 
M. extensor digiti quinti proprius, 

97,112, 114 
M. extensor indicis, 99, 77-7 
M. extensor pollicis brevis, 95-96, 

772, 114 
M. flexor carpi radialis, 107-108, 

775, 775 
M. flexor carpi ulnaris, 104-105, 

775, 775 
M. flexor digitorum profundus, 108- 

109,775, 775 
M. flexor pollicis brevis, 110-111, 

775 
M. infraspinatus, 90, 707 
Mm. interossei, 112-114, 775 
M. interosseus dorsale, 109-110, 

77^, 775 
M. latissimus dorsi, 83-84, 107 



Altenbach — Vampire Locomotor Morphology 137 



M. levator scapulae, 79, 107 

M. occipito-pollicalis, 73-74, 107, 

110 
M. omocervicalis, 83, 107 
M. opponens digiti quinti, 115 
M. palmaris longus, 105-107, 7i3, 

115 
M. pectoralis, 100-102, 770 
M. pectoralis abdominalis, 102, 7 70 
M. pronator teres, 108, 7 75 
M. propatagialis proprius, 74-75, 

772 
M. rhomboideus, 81, 83, 7C7 
M. serratus anterior, anterior divi- 
sion, 79,107, 111 
M. serratus anterior, posterior divi- 
sion, 50, 81,107, 110, 111 
M. spinodeltoideus, 87, 89, 707 
M. spinotrapezius, 78-79, 707 
M. subclavius, 99-100, 1 10, 1 1 1 
M. subscapularis, 84, 77 7 
M. supinator, 95, 772 
M. supraspinatus, 89-90, 707 
M. teres major, 84, 707 
M. teres minor, 89 
M. triceps brachii, 90-92, 705 

Osteology 

cervical vertebrae, 53 
clavicle, 59-60 

articulation with scapula, 59- 
60 



digit I, 66, 67, 68 
digit II, 66, 67, 69 
digit III, 66, 67, 69-70 
digits IV-V, 66, 67, 70-71 
humerus, 60, 67, 62-64 

articulation with radius and 
ulna, 64 

articulation with scapula, 58, 
62 
lumbar vertebrae, 54-55 
manus, 66, 67 , 68 
radius and ulna, 63, 64-66 
ribs, 56 

sacral vertebrae, 55 
scapula, 56, 57, 59, 80 

articulation with clavicle, 58, 
59-60, 80 

articulation with humerus, 58, 
62,80 

orientation, 58, 59-60, 80 
sternum, 54, 55-56 
thoraic vertebrae, 53-54 
ulna {see radius and ulna) 

Photographic techniques 
electromyographic, 6, 7-8 
motion picture, 6, 7 
still, 5, 7 

Positional terminology, 52, 53 



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