'm. ^m ^'

M4£a»5SKf<SSgi

rb

o){^<:f^^JP^. v:5"<;2

^

'-Li:£^

t

_^

^

Digitized by the Internet Archive

in 2010 with funding from

Boston Public Library

http://www.archive.org/details/batstheiryoungOOwild

{REPRINTED FROM THE POPULAR SCIENCE MONTHLY FOR OCTOBER, 1875.]

BATS AND THEIR YOUNG.

By Peof. BUET G. WILDEE.

EXCEPTING tlic colder regions, all parts of the world are inhab-
ited by bats. There are many kinds, and they often occur in
very large numbers. Probably there ai'e very few persons, young or
old, who have not seen a bat. Yet, aside from professed natm-alists,
it is equally probable that there are still fewer who, from direct obser-
vation, could give any accurate description of their appearance or
their habits, their structure, or their relations with the " birds of the
air," or the " beasts of the earth," to both of which bats bear more or
less resemblance.

Nor is this strange ; for bats pass the day in caves and deserted
buildings, and fly about in pursuit of prey only in the twilight. Much
less rapid than that of birds, their flight is so irregular as to render
it difficult to follow their course, and in the dusk they are often mis-
taken for somewhat eccentric members of the swallow family.

Their very aspect is repulsive ; they often emit an unpleasant
odor ; and, worse than all, there is reason for believing them to serve
as the vehicle by which the Gitnex lectularius, that terror of house-
keepers, has sometimes gained entrance to habitations where its
presence would never have been suspected.

When taken they bite so fiercely that we may be thankful that
they are no larger, and that, as a rule, they prefer insects to human
beings as food. No tiger could be more violent in its demonstrations
or more capable of using its only weapons, the sharp, almost needle-
like eye-teeth.

This accounts for the I'arity of instances of the domestication of
bats, and this, in part, for the difiiculty of making any extended obser-
vations upon them. Having found recorded but two such cases, I
will begin my account of bats in general with a brief history of one
individual which I succeeded in taming quite thoroughly. It was

when I was a boy, and the details have escaped me, but the main facts
are as follows :

One of our common bats (probably either the " little brown bat,"
Yespertilio suhulatus, or the " little red bat ") flew into the house one
evening and was caught under a hat. It squeaked and snapped its
little jaws so viciously that all efforts toward closer acquaintance were
postponed until morning.

When uncovered the next day it seemed as fierce as before, but
less active in its movements, probably overpowered by the glare of
daylight. When touched its jaws opened wide, the sharp teeth were

Fig. 1.— Common English Bat {VespertUio communis).

exposed, and from its little throat came the sharp steely clicks so char-
acteristic of our bats. Nor did this fierce demeanor soften in the
least during the day, and when night approached I was about to
let it go, but the sight of a big fly upon the window suggested an
attempt to feed the captive. Held by the wings between the points
of a pair of forceps, the fly had no sooner touched the bat's nose than
it was seized, crunched, and swallowed. The rapidity of its disap-
pearance accorded with the width to which the eater's jaws were
opened to receive it, and, but for the dismal crackling of skin and
wings, reminded one of the sudden engulfment of beetles by a hun-
gry young robin.

A second fly went the same road. The third was more deliber
ately masticated, and I ventured to pat the devourer's head. Instantly
all was changed. The jaws gaped as if they would separate, the
crushed fly dropped from the tongue, and the well-known click pro-
claimed a hatred and defiance which hunger could not subdue nor
food appease. So at least it seemed, and I think any but a boy-natu-
ralist would have yielded to the temptation to fling the spiteful creat-
ure out of the window. Perhaps, too, a certain obstinacy made me
unwilling to so easily relinquish the newly-formed hope of domesti-
cating a bat. At any rate, another fly was presented, and, like the
former, dropped the moment my fingers touched the head of the bat.

With a third I waited until the bat seemed to be actually swallowing,
and unable to either discontinue that process or open its mouth to any
extent.^

Its rage and perplexity were comical to behold, and, when the fly
was really down, it seemed to almost burst with the eiFort to express
its indignation. But this did not prevent it from falling into the
same trap again ; and, to make a long story short, it finally learned
by experience that, while chewing and swallowing were more or less
interrupted by snapping at me, both operati©ns were quite compatible
with my gentle stroking of its head. And even a bat has brains
enough to see the foolishness of losing a dinner in order to resent an
unsolicited kindness.

In a fcAV days the bat would take flies from my fingers ; although,
either from eagerness or because blinded by the light, it too often
nipped me sharply in its eflbrts to seize the victim.

Its voracity was almost incredible. For several weeks it devoured
at least fifty house-flies in a day (it was vacation, and my playmates
had to assist me), and once disposed of eighty between daybreak and
sunset.

This bat I kept for more than two months. It would shuflle across
tlie table when I entered the room, and lift up its head for the expected
fly. yfh&u traveling it was carried in my breast-pocket.

In the fall it died, either from overeating or lack of exei'cise, for
I dared not let it out-of-doors, and it was so apt to injure itself in the
rooms that I seldom allowed it to fly.

I should add that it drank frequently and greedily from the tip of
a camel's-hair pencil.

The following bits of bat biography are from White's "Natural
History of Selborne," and the " Annals and Magazine of Natural His-
tory:"

" Having caught a lively male specimen of the common ' long-eared
bat ' {Plecotus auritus) and placed the little fellow in a wire-gauze
cage, and inserted a few lai'ge flies, he was soon attracted by their
buzz, and, pricking up his ears (jvist as a donkey does), he pounced
upon his prey. But, instead of taking it directly into his mouth, he
covered it with his body and beat it by aid of its arms, etc, into
the bag formed by the interfemoral membrane. He then put his head
under his body, withdrew the fly fx'om the bag, and devoured it at
leisure,

" This appeared to be always the modus operandi^ more or less clev-
erly performed. Several times, when the fly happened to be on the
flat surface of the ground, the capture appeared more difficult, and my
little friend was, by his exertions, thrown on his back. The tail could

. ' I did not understand this at the time. If my I'eaders will try it, they will find that
it is A'ery difficult to even begin to swallow with the mouth open, and almost impossible
to prevent the morsel from descending after reaching the back of the throat.

then be seen turned round, with its tip and tlie margin of the mem-
brane pressed against the stomach, forming a capital trap, holding
the fly, the captor remaining on his back till he had withdrawn the
fly from the bag.

" I had no opportunity of observing the action when the bat was in
full flight ; but, if the insect was captured a few inches from the side
of the cage, the mode was the same ! When flying, the interfemoral

Fm. 2.— LoNG-EABED ENGLISH Bat (Plecotus aiiHtus).

membrane is not extended to a flat surface (and appears not capable
of being so stretched), but always preserves a more or less concave
form, highly calculated to serve the purposes of a skim-net to capture
insects on the wing.

^'Occasionally, v»'hen the bat was sleepy, sitting at the bottom of
the cage, nodding his head, a poor, silly ' blue-bottle fly,^ no doubt
of tender age, and not read in the natural history of the Vespertilio-
jiidoe, with the greatest confidence walked quietly under the bat,
passing nose, ear, and eyes, without danger ; but, immediately he
touched the sensitive membrane of the bag, it was closed upon him,
and there was no retreat except by being helped out of the difficulty
by the teeth of the bat.

"I was much entertained last summer with a tame bat which would
take flies out of a person's hand. If you gave it any thing to eat, it
brought its wings round before the mouth, hovering and hiding its
head in the manner of birds of prey when they feed. The adroitness
it showed in shearing ofl'the wings of the flies, which were always re-
jected, was worthy of observation, and pleased me much. Insects
seemed to be most acceptable, though it did not refuse raw flesh when
offered. ... I saw it several times confute the vulgar opinion that

bats, when down on a flat surface, cannot get on the wing again, by-
rising with great ease from the floor. ..."

So far, we have contented ourselves with treating of bats simply
as such, and without reference to their internal structure, their rela-
tionship with other animals, or even their dilferences among them-
selves; mucli less have we approached the deeper questions of their
origin and destiny — the probabilities as to their ancestry, and the pos-
sibilities as to their more or less remote descendants.

In the same way the astronomer may, for a time, speak of a comet
only as a certain well-known celestial j)henomeiion, which may be as
obvious to the unaided vision of the ignorant as to his own. But,
sooner or later, he cannot refrain from discussing its chemical and
physical condition, its course through space, its relations to other
comets and to the stars, and, finally, its probable origin from nebu-
lous matter, and its possible transformation into a world like our own.

The comparison may be carried one step farther. For, to the igno-
rant and superstitious the sudden apparition of a blazing comet has
often been a portent of disaster, while even the intelligent shrink
with aversion from the flitting bat, and make compai-isons with evil
spirits.

Fig. 3. — Vampiee-Bat of South America {Vampirus spectrum).

It must be admitted that most bats are " uncanny " in their aspect,
and unfriendly in disposition ; while the legends of bloqd-thirsty.. vam-
pires have only too much foundation in fact. "

But it is only fair to them (the bat family) to admit that the nunir
ber of species which thus injure men and the larger animals is very
small ; and that, while all of our own bats, and most of those of other
lands, are fierce devourers of insects, and use th"eTr~sharp teeth for de-
fense against their captors, there are many kinds, especially the larger
(Roussettes, etc.), which live almost wholly upon fruits, and are, more-

6

over, quite good eating themselves. So there should be made a dis-
tinction between them as between the venomous and the harmless ser-
pents and the more and the less poisonous spiders.

Perhaps one element of distrust of the bat family arises from
their apparent non-conformity to either of the common animal types.
The bat seems to be either a bird with hair and teeth, bringing forth
its young alive, or a mammal with wings, and the general aspect and
habit of a bird. Add to these exceptional features that their attitude,
when at rest, is always head downward, and that their legs are so
turned outward as to bring the knees behind instead of in front,
and we may almost pardon the common dislike of the whole family
of bats.

Fig. 4. — Flzing-Fox or Eoussette (Pteropus rubricollis)

We may as well state at once that a bat is really a mamonal ; that
is, it agrees with moles, rats, sheep, horses, cats, monkeys, and men,
in bringing forth its young alive, and nursing them by milk ; in hav-
ing red blood-corpuscles, which contain no nucleus ; in being clothed
with hair; and in possessing a corpus callosum, that is, a band of
fibres connecting the two cerebral liemispheres.

There are other anatomical features which link the bats closely
with the moles and shrews and hedge-hogs. Indeed, the bat might be
described as a flying mole, or the mole as a burrowing bat.

Twenty years ago one of these phrases might have been as accept-
able as the other ; for they would have implied only an ideal connec-
tion between the forms. But now, when the idea of an actual evolu-
tion or derivation of widely-difierent forms from one another, or from
common stocks, is rapidly becoming the fundamental postulate of aJl
biological research, we are bound to inquire whether one mode of ex-
pression is not much more likely to be true than the other.

For the solution of this, as of most such inquiries, wejnust^ appeal
to embryology, to the study of the development of animals, aiid of
The^re^eifil^laiices between the earlier stages of some and the later
stages of others.

Our first object is to confirm the conclusion that bats are mammals
rather than birds. And here, strangely enough, we find that the mat-
ter of size, usually regarded as of little moment in zoological discrimi-
nation, becomes of primary importance. All animals, mammals as
well as birds, are formed from eggs. An egg, or ovum, is a cell with
special endowments, and capable of availing itself of the peculiar con-
ditions under which it is placed, the first of these conditions being the
access of the zoosperms of the male. Now, the eggs of all mammals
are small, usually microscopic. The human ovum is about ^ks ^^ ^.n
inch in diameter.

Therefore, although the yolk or essential part of the eg^y of a
humming-bird may be pretty small, it is far larger than the largest
mammalian ovum ; while that of the ostrich or the Epyornis is sim-
ply gigantic in comparison.

Now, I am not aware that the ovum of a bat has ever been exam-
ined, but there can be doubt of its minuteness as compared with that
of any known bird. Fig. 5 shows, of its natural size, the earliest em-
bryo of a bat I have ever heard of Its length as it lies is much
less than that of a humming-bix'd's egg. Moreover, since the young
bird is developed upon tlie yolk, and the latter remains of consider-
able size until very near the period of hatching, and since the yolk of
our little bat either has been already absorbed or is too minute for
detection, it may be considered that it was much smaller than that of
birds.

Finally,^the simrpte- fact that the little bat was taken out of tlie
mother already somewhat advanced in development, is clear proof
that it is not a bird.^

Aside from the absence of yolk, the form of the smallest embryo,
above figured, might not determine its mammalian nature ; but the
remaining figures, however little some of them may resemble quadru-
peds, are evidently not birds. /_The tail is too long (for any bird ex-
cepting the Archeopteryx) ; the muzzle is rounded, the feet have five
divisions more or less marked, while no bird has more than four toes ;
and, although the hands may in some cases resemble a bird's wing, yet
here too are five fingers, and the wing is evidently an expansion of
the hand itself by the elongation and separation of the fingers, I'ather
than a slender hand with feathers attached to the hinder border as with
birds.

' There are no known birds which normally produce living young; but I have a
chicken-like body nearly three inches long, which was developed within the hen. It was
shown at the meeting, of the American Association for the Advancement of Science, this
year. Its exact nature can only be learned after full examination of the structure.

With the more advanced embryos the prominent ear would be con-
clusive against their avian nature, and the nostrils, where they show,
are not those of birds.

We may, then, dismiss from our minds any anxiety as to whether
bats are partly birds and partly mammals, and conclude merely that,
upon the essential mammalian structure, there have been superinduced
features which enable the bat to fly in the air ; these, howeA'er, no
more making it a bird than the form and habit of the whale and mana-
^g render them fishes.

The second question is, whether bats are to be regarded as the pro-
genitors or the descendants of the moles and slirews ; or, to put it
more accurately (since the idea of derivation does not imply that living
species have descended from other living species, but from similar
extinct species or from others which combined features since separated
in the two forms), is it proV^able that the existing bats have been pro-
duced from original stocks moi*e nearly resembling the moles or the
reverse ? That the foriiier is the more probable, is indicated upon three
grounds :

1. The bat form is peculiar among mammals, and does not, like the
Ornithorhynchi(s and Echidna^ manifest any mternal structural aflSnity
with birds. There is a much more marked resemblance to the extinct
flying reptiles {Pterodactyli)^ but this is probably one of analogy.

2. The embryo bat resembles the ordinary small mammal ; the long
fingers, the persistence of the web between them, and its continviation
from the border of the body and tail, are features of later appearance.

3. In one embryo (Fig. 9), the thinness and prolongation of the
muzzle as compared with the lower jaw may be compared with the
elongated snouts of the " star-nosed mole " and the " elephant shrew."

I have never had the opportunity of examining the young of moles
or shrews. This would be very desirable, and, one would think, not
difiicult to accomplish.

Figs. 5 to 11 are intended chiefly to show the gradual develop-
ment of the limbs, so the other parts are drawn with less detail, and
no attempt is made to elucidate the manner of formation of the face
from the visceral arches.

The series begins with Fig. 5. Here the body is simply an elon-
gated mass, longer and rounded at the head end, and tapering at the
other extremity. It is twisted upon itself, as is often the case with
young embryos. The yolk-sack and membranes are not well preserved,
and are not shown at all in the figure. This embryo maybe regarded
as quite small for even a bat. The limbs have not appeared, so the
tail does not form a distinct prolongation. (The lower figure is of
natural size ; the upper is enlarged five diameters.)

In Fig. 6 the arm {ar) and leg {pes) project as little flat pads
from the sides of the body. There is no sign of subdivision into fingers
and toes, and very little difiierence between the two limbs. It is worth

Fig. 5.

Fig.

Fig. ".

Fig. 9.

Fig. 11.

Fig. 10.

Emeeto Bats. All, exceplinef Fig^ 11, enlarged S diameters.
Explanation of Plate}
Figs. 10 and 11 from the little brown bat (Vespertillo svbulatus), the others from a Brazilian spe-
cies {Nyctirwmus Brasiliensis) \ Fig. 11 and the smaller part of Fitr. 5 are ofnatural size. All
the others are enlarged 5 diameters ; that is, 25 areas. The lettering is uniform, as follows :
u c, umbilical cord; not seen in 5 or 8. iT, head ; T, tail ; Ar, armus or anterior limb ; Pes.
foot ; P, pollex or ttiurnh, the anterior digit of the manus ; Pr, primus or ffreat-toe, the ante-
rior dactyl of the pes, which becomes the outer in the older bats, but is the inner with most
animals ; W, web, the fold of skin which connects the digits with each other and with the leg
and margin of the trunk ; C, calcar, a spur-like process from the heel, serving to extend the
web which reaches between the legs and the tail ; Ear. the ear ; in Fie. T ^is the heart ; in Fig.
lOylis the rounded prominence corresponding to the cerebral hemispheres which are developed
from the anterior cerebral vesicle; M represents the optic lobes, formed from the middle
vesicle ; N., nostril ; J/o, mouth ; E, elbow ; K, knee. For further explanation, see the text.

^ Figs, 5 to 11 were all drawn and en^aved from nature by Mr, Philip Barnard.

2

10

noting, however, that the manus is already a little the wider and more
prominent.

In Fig, 7 the manus is not only larger but h^-s protruded so as to
display the wrist and elbow regions, and a slight prominence upon the
anterior border marks the position of the thumb (pollex). In these
three specimens I have not as yet found the ear, but in 3 and 4 the
eye is quite apparent.

In Fig. 6 the ear is a triangular flap, as in most early mammalian
embryos.'

The manus and pes have enlarged and present shaded portions
corresponding with the thinner tissiie between the finger and toes.
In the fonner this is to become the web ; in the latter it is wholly re-
moved so as to leave the toes free. The muzzle is partly covered by
the manus, but it is already somewhat pointed, as in the next figure.

In Fig. 9 the manus and pes of the left side are shown as if re-
moved from the trunk, so as to expose the flat and prominent muzzle.
The ear is a large flap, but still projects forward so as to cover the
opening. The pollex has separated from the other digits, and the
latter are elongated and bent downward. The pes is longer and the
signs of subdivision more distinct. A web connected the limbs and
the trunk as in the older specimens, but it was somewhat torn, so that
the exact extent could not be determined, and I preferred to wait for
a better specimen to show it.

The specimens above described were taken from a Brazilian species,
Nyctinomiis Brasiliensis (which is also found in this country). Figs.
10 and 11 were from the common " little brown bat " ( Vespertilio subu-
latus). As might be expected, the increasing limbs are packed about
the body more or less irregularly. But in Fig. 10 the limbs of the two
sides are placed with almost exact symmetry so as to cover the face
and the body. One eye is covered, the other peeps out over the index-
finger. The ears are firmly held down by the thumbs, and one of the
nostrils is partly hidden by the web. The lower part of the trunk
and the tail are bent upward, and the knees are thrown outward so as
to bring the great-toe {pr) upon the outer instead of the inner side.
The whole suggests an efibrt upon the part of the embryo to not only
occupy the" least possible space, but also to screen itself from obser-
vation, and neither see, nor hear, nor smell.

In Fig. 11 is shown an older embryo, of natural size, outspread so
as to display the characteristic features of bats ; the greatly-elongated
fingers ; the separation of the thumb ; and the extension of the web,
with the reticulated arrangement of vessels and nerves upon it. This
nervous expansion seems to enable bats to perceive the proximity of
bodies by the change in the pressure of the air.

' It remains to be seen whether the seals, whales, manatee, and dugong, have a pinna
in the earlier stages, and afterward lose it. Upon the earliest embryo of a manatee yet
known, see a paper by the writer in American Journal of Science^ August, 1875.

11

The Size of Bat Families. — It is not known that Kl^c make a nest
like birds, or that they have any other way of caring foi\^eir young
than by carrying them hanging to their fur whether cluringsfliglit or
while suspended at rest by the legs. \

So we might naturally infer two things: first, that the young ^ats
would be born in a somewhat advanced condition so as to be able a?^s
soon as possible to shift for themselves ; and, second, that the number
produced at a birth would be small.

The former inference would seem to be true, judging from the
large size of the little bats before birth, and the rarity of the cap-
ture of the mothers with young. In one case the two unborn young
weighed two-thirds as much as the parent, and the average of twenty
individuals gave the weight of the young as four-tenths that of the
parents.

Upon the second point it is stated by Van der Hoeven ("Hand-
book of Zoology," vol. ii., p. 731) that "bats commonly produce one
or two young ones at a birth ; " but he. does not say upon how many
observations the conclusion is based.

Prof. Owen (" Comparative Anatomy of Vertebrates," vol. iii.,
p. 730) records two observations of bats [Vespertilio emarginatus and
T^ noctula)^ with each one young, and concludes that this is commonly
the case with all bats.

A collared fruit bat ( Cynonycteris collaris) produced a single young
February 27, 1870, and a second April 7, 1871.^

In Jamaica Mr. Osborn observed several females of Molossus fu-
marius and Monophyllus poeyi^ with each one young.*

The same observer mentions two other species (Macrotus Water-
housii, and Monophyllus Redinanii)^ without specifying the number
of young ; but we may infer that, as in the other cases, each female
had but one.

In a single female of an undetermined Brazilian species I have
found one young; and in each of forty females of the NycUnomus
£rasiliensis (from Brazil) a single young.

These are certainly facts in corroboration of the opinions of Owen
and Van der Hoeven, but let us not be hasty in generalizing from
them respecting all bats.

In June, 1874, there were brought to me twenty females of the
" little brown bat " ( Vespertilio suhulatus). Each was found to con-
tain two little bats in various stages of development.^

Finally, Prof. Putnam, of the Peabody Academy of Science, has
kindly allowed me to examine two females of the Lasiurus novebora-
censis taken in Massachusetts, on each of which were three young bats.

The foregoing observations indicate that, while one is the more

1 P. L, Sclater, "Proceedings of Zoological Society, 1870, 1871."
^ " Proceedings of Zoological Society, 1865," p. 81.
; 3 I have since seen a bat of anotiier species, to which were clinging two young.

/'■ ' 12

common nmnber of young produced by bats, two and three may
occur. More extended inquiry may show that these larger families
are less rare than now appears, and even that as many as four young
may be produced at a birth. For while bats are usually credited with
only two nipples, an extra pair exists upon the Lasiurus novehorcf
e^nsis.

The uniformity in number with each species is very striking.
Twenty-two of one species had each two young, while forty of another
had each one.

In the former case the young were placed one on the right and the
other on the left of the body. But in the latter case the single young
was invariably on the right side ; while, in the single specimen of the
undetermined Brazilian bat, the young was on the left side.

Equally sti-iking with the above facts is the isolation of the females
with yourjg. Among forty-three Nyctinomus Brasiliensis was but a
single male. No males were found near the twenty-two Yespertilio
suhulatus, Osborn says that, of Molossus fumarius, all of one large
lot were males ; while at another time, in a large hollow tree, he found
in one cavity about one hundred males, and in a second about the same
number of females, with " apparently a few males here and there."

Evidently there is much to be learned respecting the domestic and
I social economy of these animals. Perhaps the males gather food for
the females.'

Perhaps the most important fact, from a practical point of view,
is that of the power of the mother-bats to carry such a weight of
jyoung in addition to their own. Yet, so far as I know, all estimates
iof the extent of wing and size of muscle, which would be necessary
^ to enable a man to fly, have been based upon the idea that the only
■flying mammal is a fair standard.^

These estimates should be cort-ected so as to conform to the fact
that a bat can fly with nearly double its ordinary weight. Even this
may not encourage us to hope for a future race of flying-men. But it
renders it worth considering whether a man, naturally slight of frame,
with small head, could not so far reduce his weight by a flesh diet, and
by the amputation of his legs, as to enable him, by special cultivation
of his pectoral muscles, to work efiectively a pair of wings less exten-
sive than those now supposed to be required,

' The writer has not been able to examine the development of bats with the nasaJ
appendages. He would be glad to receive information upon the habits of bats with young,
and to exchange the latter for specimens of AmpMoxus.

^ Harting (" Archives Neerlandisches," iv.) calculated that a bat the size of a man
would require wings two and a half metres long, and with a surface of one and a half
square metre.

Boston Public Library
Central Library, Copley Square

Division of
Reference and Research Services

The Date Due Card in the pocket indi-
cates the date on or before which this
book should be returned to the Library.

Please do not remove cards from this
pocket.

BOSTON PUBLIC LIBRARY

3 9999 06626 764 0