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NOAA TECHNICAL MEMORANDUM
NMFS-SEFSC-383

Movements, Site Fidelity, and Respiration Patterns
of Bottlenose Dolphins on the Central Texas Coast

By
Bernd Wiirsig and Spencer K. Lynn

U.S. Department of Commerce

National Oceanographic and Atmospheric Administration

National Marine Fisheries Service

Southeast Fisheries Science Center

75 Virginia Beach Drive

Miami, FL 33149

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June 1996

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NOAA TECHNICAL MEMORANDUM
NMFS-SEFSC-383

mot'*'

Woods Hoie Oceanographlc
Institution

Movements, Site Fidelity, and Respiration Patterns
of Bottlenose Dolphins on the Central Texas Coast

By
Bernd Wursig and Spencer K. Lynn

U.S. DF.PARTMENT OF COMMERCE
Mickey Cantor, Secretary

NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION
D. James Baker, Administrator

NATIONAL MARINE FISHERIES SERVICE

Roliand A. Sclimitten, Assistant Administrator for Fisheries

June 19%

This Technical Memorandum series is used for documentation and timely communication of prelim niary
results, interim reports, or similar special-purpose information. Although the memoranda are not subject
to complete formal review, editorial control, or detailed editing, they arc expected to reflect sound
professional work.

NOTICE

The National Marine Fisheries Service (NMFS) does not approve, recommend, or endorse any
proprietary product or material mentioned in this publication. No reference shall be made to
NMFS, or to this publication furnished by NMFS, in any advertising or sales promotion which
would indicate or imply that NMFS approves, recommends, or endorses any proprietary product
or proprietary material mentioned herein, or which has as its purpose or intent to cause directly
or indirectly the advertised product to be used or purchased because of NMFS publication.

This report should be cited as follows: Wursig, B. and S. K. Lynn. 1996. Movements, site fidelity,
and respiration patterns of bottlenose dolphins on the central Texas coast. NOAA Tech. Mem. NMFS-
SEFSC-383, I 1 I pp.

Authors' aftlliations: Texas A«feM University, Marine Mammal Research Program, 4700 Avenue U,
Bidg. 303, Galveston, TX 77551.

Copies may be obtained by writing the Southeast Fisheries Science Center, the primary author,
or:

National Technical Information Service
5258 Port Royal Road
Springfield. V A 22161
Telephone: (703)487-4650
FAX: (703)321-8547

Rush Orders: (800) 336-4300

This is Southeast Fisheries Science Center Contribution MlA-95/96-40.

Movements, Site Fidelity, and Respiration Patterns of Bottlenose Dolphins on

the Central Texas Coast: A Report to the National Marine Fisheries Service,

Southeast Fisheries Science Center, Miami, Florida

By

Bemd Wursig and Spencer K. Lynn

Texas A&M University

Marine Mammal Research Program

4700 Ave. U, Bldg. 303

Galveston, TX 77551

ABSTRACT

Radio-tracking of 10 bottlenose dolphins (Tursiops truncatus), from 9 July
1992 to 13 September 1992, and photographic surveys of 35 freeze-branded
dolphins, from May 1992 to June 1993, were conducted in the Matagorda Bay
area of Texas, in response to a mass mortality event which occurred between
Matagorda and Aransas Bays, Texas, during spring 1992. The primary goals of
the study were to assess range size and site fidelity, as well as to initiate a long-
term ecological study by collecting data on social and behavioral patterns.

The Matagorda Bay dolphin population was found to be numerically
robust, occupying all regions of the bay surveyed. Mean range size, based on
radio telemetry, was 140 km^ (SD = 90.7, n = 10 dolphins). Males and females
had similar range sizes though males visited the extremities of their ranges
more frequently or for longer periods. Several generalities were observed:
(1) Dolphins were capable of, and often did, traverse their range in several
hours. (2) Dolphins traveled widely on some days, perhaps crossing their own
ranges, while on other days movement was very confined, within 1-2 km^.
This did not appear to have a temporal or geographic pattern. (3) Dolphins
tended to spend about 1-4 days in a particular portion of their range.

(4) Movement tended to be more confined at night than during daytime.

(5) Dolphins tended to visit the extremes of their ranges only in the daytime.
The assertions of (4) and (5) may be biased as a result of less sampling effort at
night, with fewer triangulations than during daytime and no visual sightings.

Ill

Most, if not all, of the 35 freeze-branded dolphins apf)eared to be resident
to the Matagorda-Espiritu Santo Bay area with much fluidity of group
membership. Overall mark/recapture population size estimates from photo-
identification suggested that 218 ± 71.4 (95% CI) dolphins utilized an area of
312 km^ in Matagorda and Espiritu Santo Bays, similar to an estimate made in
1981. Dolphins spent longer times at the surface and dove less often at night,
indicating lower activity levels at night. Observations of long-distance
movement between Texas bays, and an autumn increase in dolphin numbers
in the study area, suggested that the study aiumals were not an isolated
population.

IV

ACKNOWLEDGMENTS

Radio-tracking 10 dolphins simultaneously and for 24 hr/day is quite an
undertaking, and we had outstanding and very dedicated assistance in the
field from Windi Allman, Stacie Arms, Angela Beaty, R. A. Blaylock,
R. H. Defran, Lisa delos Santos, Kellie Fashe, Dagmar Fertl, Anna Forest,
Claire Graham, Adam Grundt, Cara Gubbins, Mike Jackson, D'ann
Jorgenson, Tom Kiekhefer, Linda Price-May, Kim McDaniel, Janet Morrison,
Jan Robinson, Andrew Schiro, Steve Schneider, Lisl Shoda, J. Holly Smith,
Bill Stevens, Gil Swain, Wang Ding, Wang Qin, David Weller, Brian
Wilson, Kim Wiirsig, and Melany Wiirsig. Additionally, Angela Beaty,
Nathalie Clauss, Morgan Collins, Mark Dhruv, Holly Fortenberry, Janet
Morrison, Ashlesha Patel, Tracy Salvi, Meike Scheidat, Andrew Schiro,
Sandy Smith, Tamara Svoboda, and David Weller helped vdth analysis of
the over 4,500 photos, and data entry of the over 1,500 bearings and 28,000
min of surfacing intervals. Of course, none of this would have been possible
without the help of the National Marine Fisheries Service (NMFS); and the
capture, veterinary, and physiology teams. We tharJc especially Larry Hansen
and Gerald Scott of NMFS; Jay Sweeney and Rae Stone of Dolphin Quest and
Waikoloa Marine Life Fund; and Graham Worthy and Tamara Miculka of
the Texas A&M Uruversity Marine Mammal Research Program. Thomas
Healy of the U. S. Fish and Wildlife Service, Ted Fuller of the U.S. Coast
Guard, and Norman Boyd of the Texas Parks and Wildlife Department were
especially helpful with local logistics. Our pilots were Sam Sailor (Piper Cub),
Allan Potter of the U.S. Coast Guard Reserve (Cessna 172), and Mike
Newcome of Gal v Aero (Cessna 177).

This work was carried out under NMFS Permit #728 to Wiirsig and
Worthy and SeaGrant Project #R/ES-55. The capture, sampling, and tagging
was conducted by the SEFSC under an emergency authorization conferred
pursuant to Section 109(h) of the Marine Mammal Protection Act. This report
was improved by comments from Alejandro Acevedo, Colin Allen, Ben
Blaylock, Larry Hansen, Nova Silvy, Gary Varner, and Dave Weller.

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VI

TABLE OF CONTENTS

Page

ACKNOWLEDGMENTS v

LISTOPHGURES ix

LIST OF TABLES xi

INTRODUCTION 1

METHODS 2

RADIO-TRACKING 2

Radio Package Specifications 2

Package Mounting 3

Signal Reception System 3

Data Collection 4

Data Analysis 4

PHOTOGRAPHIC TECHNIQUES 5

Study Site 5

Data Collection 5

Data Analysis 7

RESULTS 10

MOVEMENT PATTERNS 12

SURFACING PATTERNS 14

ASSOCIATIONS AMONG INDIVIDUALS 16

BEHAVIOR 18

POPULATION SIZE 19

HEALING OF BIOPSIES 20

DORSAL HN NOTCHES 20

DISCUSSION 21

MOVEMENT PATTERNS 21

Vll

SURFACING PATTERNS 26

ASSOCIATIONS AMONG INDIVIDUALS 27

BEHAVIOR 29

POPULATION SIZE 30

HEALING OF BIOPSIES 31

DORSAL FIN NOTCHES 33

CONCLUSIONS 33

LITERATURE CITED 35

HGURES 45

TABLES 63

APPENDIX 1. SUMMARY INFORMATION FOR ALL DOLPHINS

CAPTURED : T7

APPENDIX 2. SUMMARY OF CAPTURE INFORMATION 81

APPENDIX 3. RESIGHTINGS OF NON-RADIO-TAGGED

DOLPHINS 85

APPENDIX 4. SEMI-WEEKLY POSITIONS OF RADIO-TAGGED

DOLPHINS 91

APPENDIX 5. DIURNAL POSITIONS OF RADIO-TAGGED

DOLPHINS 101

APPENDIX 6. SUMMARY OF OBSERVATIONS ON BIOPSY

WOUNDS 107

Vlll

LIST OF HGURES

Page

Figure 1. Map of the Port O'Connor area of Matagorda Bay 45

Figure 2. Left and right sides of a dolphin dorsal fin (FB502)
showing radio package placement (a) and magnesium
nuts (b) 46

Figure 3. Example triangulation for FB518 at 1045 hr, 11 August 1992,
from Home Base, in Port O'Coru^or, and a tracking vessel
at the base of the western Matagorda Ship Channel jetty 47

Figure 4. Photographic survey effort. May 1992-June 1993 48

Figure 5. Sightings of freeze-branded dolphins across surveys 49

Figure 6a. Summary ranges for radio tagged dolphins FB501 and
FB502, from radio telemetry and sightings. May 1992-
June 1993, with information on age and sex 50

Figure 6b. Summary ranges for radio tagged dolphins FB504 and
FB505, from radio telemetry and sightings. May 1992-
June 1993, with information on age and sex 51

Figure 6c. Summary ranges for radio tagged dolphins FB514 &
FB515 (1), FB511 & FB522 (2), and FB518 & FB521 (3), from
radio telemetry and sightings. May 1992-June 1993, with
information on age and sex 52

Figure?. Positions of FB518 by time of day, 15 June 1992-13

September 1992, from radio telemetry and sightings 53

Figure 8. Approximate noon positions for dolphin FB518, 15 June
1992-13 September 1992, from radio tracking and
sightings (two subsequent sightings on bold) 54

Figure 9. Relative frequency histograms of dive durations during

day (a) and night (b) 55

Figure 10. Affiliations of all female and calf (a) and male (b) freeze-
branded dolphins (as measured by dolphins occurring in
the same group in a sighting). May 1992-June 1993 56

IX

Page

Figure 11. Plots of relative percents of behaviors by survey (a) and

hour of day (b) 57

Figure 12. Mean group sizes by survey (a) and hour (b), error bars

indicate 1 SD 58

Figure 13. Mean group sizes by behavior, error bars indicate 1 SD 59

Figure 14. Histogram of observed travel directions 60

Figure 15. Assumed minimum area occupied by estimated dolphin

population 61

LIST OF TABLES

Page

Table 1. Summary of radio tracking effort 63

Table 2. Summary of photographic survey effort 64

Table 3. Summary statistics for surfacing interval data 65

Table 4. Mean half-weight index of association values for non-calf

freeze-branded dolphins seen at least five times 68

Table 5. Mean half-weight index of association values for same-
sex and opposite-sex associations among freeze-branded
dolphins 70

Table 6. Primary and secondary affiliates of the six female and
eight male freeze-branded dolphins most frequently
sighted 71

Table 7. Observed frequencies of behaviors in each habitat type 73

Tables. Mean direction of travel for eight surveys 74

Table 9. Bailey-modified Petersen estimates of population size 75

Table 10. Stages of wedge-biopsy healing 76

XI

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xu

INTRODUCTION

In March and April 1992, 111 bottlenose dolphin carcasses were recovered
from the area between Matagorda and Aransas bays of the central Texas coast
(Fig. 1). This represented an unusually high mortality, compared to a mean of
14 (SD = 71, range = 5-23) deaths during March-April calculated from the
previous 5 yr (Elsa M. Haubold, Operations Coordinator, Texas Marine
Mammal Stranding Network, personal commuiucation). The die-off raised
questions about dolphin movement patterr\s and site fidelity on the Texas
coast, and on the ability of potentially locally depleted stocks to recover
through immigration. In response, the National Marine Fisheries Service
funded the Marine Mammal Research Program of Texas A&M University at
Galveston (MMRP) to conduct a 6-day survey of the Matagorda Bay area. The
primary intent of the survey was to obtain data on approximate minimum
numbers of animals still alive in the area by photo-identification, general
behavior and apparent health of live animals, and the overall feasibility of
conducting long-term ecological studies on bottlenose dolphin distribution
and habitat use in this bay system.

The short preliminary study, carried out 15-19 May 1992, photo-identified
at least 67 different dolphins inhabiting the area; discovered no apparently
moribund dolphins among the live animals; and resulted in the strong
recommendation that detailed research, relying on tagging, physiological
studies, and long-term radio-tag and photographic monitoring were essential
to an understanding of dolphin use of the Matagorda Bay environs.

Consequently, to assess the impact of the spring 1992 die-off, a National
Marine Fisheries Service-sponsored capture effort from 7-19 July 1992
resulted in collection of physiological information from 36 dolphins
(Sweeney 1992, Graham A. J. Worthy, Director, Texas Marine Mammal
Stranding Network, personal communication). The 36 dolphins received
dorsal fin roto-tags (Scott et al. 1990b, Sweeney 1992); 35 were freeze-branded
on both sides of the upper dorsum and /or dorsal fin (Odell and Asper 1990,
Scott et al. 1990b, Sweeney 1992); and 10 were fitted with radio transmitters
(Evans 1971, Wvirsig et al. 1991).

The primary objectives of this study were to gather information on range
characteristics and site fidelity, and to begin a long-term study of dolphins in
the area by examining movement patterns, associations among individuals,
and other ecological data. The results of radio-tracking and photographic
monitoring are described here. Radio-tracking was from 9 July 1992 to
13 September 1992, when radio signals were no longer received. Photographic

monitoring of freeze-branded dolphins is presented for the periods of May
1992 through June 1993.

METHODS

Matagorda Bay, on the central Texas coast (28°30'N, 97°20'W), is
characterized by wide seasonal swings in temperature and salinity. Over the
bay as a whole, mean salinity ranges from 12.7 in spring to 16.5 in
summer/winter (Orlando et al 1993). In the study area, salinities ranged from
X = 17.3 ppt (SD = 11.12, n =119) in spring/early summer to 27.0 ppt in late
summer (SD = 6.40, n = 97) (Wiirsig, unpublished data). Temperature was
sampled less frequently but was 12-15 °C (« = 3) in winter and x = 31.3 °C in
late summer (SD = 1.31, n = 6) (Wiirsig, unpublished data).

For radio-telemetric and photographic data analyses, statistical tests were
run with StatView 4.0fpu (Brainpower 1986) and Excel 4.0 (Microsoft 1992) for
Apple Macintosh microcomputers.' Two age classes were defined for
anadytical purposes: "immature" was comprised of females < 8 yr old,
males < 10; and "mature" as females ^ 8 yr old, males > 10. The boundary ages
were based on youngest pregnant female captured and age-at-maturity results
from Fernandez (1992).

RADIO-TRACKING

Radio Package Specifications

The radio transmitters (Fig. 2), built by Telonics, Inc., Mesa, Arizona,
consisted of aluminum tubes 8.0 cm long and 1.6 cm in diameter, with a
0.1-cm thick and 39.0-cm long staiitless-steel antenna, topped by a 0.3-cm ball
to prevent injury by the tip of the antenna (configuration MOD-050
transmitter package with TAGL antenna). Transmitters broadcast in the
frequency range of 148-150 MHz, at a pulse rate of 90/min, pulse duration of
400 msec, bandwidth of 16.2 Hz, and pwwer output of approximately
10-20 milliwatts. Power was provided by sealed lithium batteries designed to
last approximately 6 weeks.

The transmitters were attached to a rectangular 12.5-cm long, 4.0-cm high,
and 0.12-cm thick aluminum plate rounded at the four comers and backed by
0.4-cm thick open-cell "wetsuit" neoprene. Trai\smitters were attached to both
the aluminum /neoprene plate and the dolphin dorsal fm by two 0.64-cm
diameter bolts fabricated from Teflon rods supplied by Cadillac Plastic and
Chemictd Co., Houston, Texas. On the radio side, the Teflon bolts were

' Use of trade-names does not imply endorsement by the National Marine Fisheries Service.

threaded with a stainless steel lock-tight nut. On the opposite side of the fin,
the bolts were threaded with a fabricated magnesiun\ alloy nut. The
magnesium alloy was supplied by Metal Supply Co., Philadelphia,
Pennsylvania. The magnesium nuts were backed by 3.5-cm-aluminum
washers, also fitted with neoprene against the skin surface. Between the
magnesium nut and the aluminum washer was a 3.5-cm-metal washer to
interact electrolytically with the magnesium and salt water. The magnesium
nuts were designed to corrode to disappearance within about 4 wk in water
25-30 °C ai>d about 20-30 ppt salinity. The magnesium nuts were 2.6 cm in
diameter and approximately l.(>-1.3-cm thick, with the rear nut slightly
thinner (by 0.1 cm) than the front nut, so that the front bolt would tend to
hold the package a few hours longer than the rear bolt, and not cause an
adverse tiuming and increased drag of the radio package, likely if the rear bolt
held longer.

Package Mounting

The radio was mounted to the dorsal fin by the Teflon bolt and
aluminum/stainless steel/magnesium nut assemblies. Two 0.60-cm-bolt
holes were punched through the fin with a standard stainless steel laboratory
cork borer disinfected with Betadine. Prior to hole punching, a veterinarian
examined the chosen location for absence of major arteries v^rith an 18-gauge
needle, sterilized the site with alcohol, and administered a local anesthetic of
1.8 cc Lidocaine (Sweeney 1992). Slight bleeding occurred about one-half of the
time and always stopped upon insertion of the tight-fitting Teflon bolts. The
bolts were custom-fit to each dorsal fin by siupping off excess bolt material
with wire cutters. The magnesium alloy nuts were finger-tightened and then
pressure-crimped with a vice-grip.

Signal Reception System

Dolphin radio-transmitter signals were received with Telonics TR-2
hand-held receivers and Telonics TS-1 hand-held automatic frequency
scanning receivers. These were used with antennas ranging from hand-held
"H" or two-element antennas (± 20° directional accuracy) to five-element
Yagi-Uda antennas (± 5° directional accuracy) on aluminum poles up to 8-m
high (Fig. 3). Receiving systems were used from each of two 5.5-7 m outboard
vessels, a pick-up truck, several secondary lemd-based stations, and two five-
element antennas on the second story balcony of a house (Home Base) in Port
O'Connor, at the southern end of Matagorda Bay (28°27.05'N, 96°25.12'W).
Total height of the Home Base antennas was approximately 14 m above sea
level, and approximate range of reception varied from 10-20 km. Twin "H"
antennas also were mounted on the wing struts of Cessna 172 and Piper Cub
aircraft and on the footsteps of a Cessna 177 for aerial tracking. Usual range

was at least 50 km from an altitude of 800-1500 m. Details of tracking from
stationary and mobile antenna arrays can be found in Mech (1983).

Data Collection

Directional bearings were taken on each dolphin every 4-6 hr for the life
of the transmitter. Bearing entries included notes on signal quality (strength
and signal to background noise), estimated distance and location (based on
operator experience), environmental conditions, and a 30-min sample of
surfacing intervals when signal quality allowed for reliable data. Bearings
were often taken simultaneously from more than one location, allowing for
triangulated positions. During daylight hours, one of the vessels often
approached tagged animals by homing onto the signal. At such times
behavioral observations, photographs, and HI8 video recordings were made;
and exact positions, useful for comparisons to estimated and triangulated
positions, were obtained. These sightings also allowed radio operators at
remote locations to calibrate their distance and location estimates. Surfacing
intervals were obtained by noting the time, to the second, when the radio
signal was first heard as the dolphin surfaced. Also noted was the number of
pulses (beeps) received while the dolphin and transmitter were at the surface.
Previous and present experience indicate that almost all surfadngs
lasting < 2.5 sec are accompanied by a single breath. Longer surface times
indicate dolphins resting at the surface, or traveling or feeding in extremely
shallow (< 0.5-m depth) water.

Data Analysis

Radio-track analysis consisted of plotting telemetered locations onto a
map, and visually inspecting for movement patterns, distances traveled, and
geographical ranges (the area over which an individual moved in the course
of the study). Ranges (Fig. 6) were plotted with Canvas 3.5 for Macintosh
(Deneba 1992) by drawing a continuous area covering all telemetered and
visually sighted positions. Range sizes were calculated using Canvas'
"Calculate Area" command (Deneba 1992) and compared between males and
females, pregnant and non-pregnant females, females with calf and those
without, and age class (Mann-Whitney U). A simple linear regression was
performed to investigate potential dependence of range size on number of
days tracked for each of the dolphir\s.

To investigate differences in range use between males and females, we
compared variance about the mean position. The mean horizontal and
vertical x-y coordinate was determined for each radio-tagged dolphin.
Horizontal and vertical deviations from the mean were calculated for each

telemetered and visually sighted position for each animal and compared by a
variance ratio F-test (Zar 1984).

Surfacing interval data consisted of dive duration, dive rate, and surface
duration. Dive duration was measured as the time interval between
surfacings. Dive rate was calculated by dividing the number of surfacings by
the duration of the sampling period (usually about 30-min). Time sf>ent at the
water surface between dives (surface duration) was indicated by the number
of pulses heard. Statistical tests were performed on these pulse counts and
subsequently transformed into the presented durations in seconds by
multiplying the pulse count by 1.5 pulses/sec, the transmitters' pulse rate.
The 30-min sampling periods were coded by time of day: "day" = 0700-19(X),
"night" = 2100-0500, and "crepuscular" = 0500-0700 and 1900-2100.

The three surfacing-interval-data types were averaged for each dolphin
over the 30-min sampling f)eriods to minimize dependence within a
scimpling period. These means were compared statistically by time of day, and
among individual dolphins (Kruskal-Wallis, followed by Fisher's LSD);
pregnant vs. non-pregnant, with-calf vs. without-calf, and sex (Mann-
Whitney U); and age, and across each other {e.g., dive duration was regressed
on dive rate and surface duration, simple linear regression).

PHOTOGRAPHIC TECHNIQUES

Study Site

The primary photographic survey area included most of the range of
radio-tracked individuals. Areas with particularly high-density coverage were
western Matagorda Bay, from Sand Point south to the Matagorda Ship
Channel Jetties; and west to eastern Espiritu Santo Bay, including Vanderveer
Island and the Ferry Channel. This area also includes the Intra-Coastal
Waterway (ICW) near Port O'Connor, and Pass Cavallo (Fig. 1). Survey effort
was not uniform (Fig. 4).

Data Collection

Photographic surveys required three people: boat-driver, note-taker, and
photographer. Unstructured, meandering censuses were conducted from 5.5-
and 7-m outboard vessels. Upon encountering a dolphin group, behavioral
and environmental data were collected on a data sheet and dorsal fin
photographs were attempted of all animals in the group (Wiirsig and Wiirsig
1977, Wiirsig and Jefferson 1990). Typically, dorsal fins were photographed
with a 35-mm camera from distances of 5-15 m with a 70-21 0-mm-zoom
lens, using 200-ISO slide film. An estimated 50-80% of Texas shore dolphins

are identifiable by natural markings {e.g., Brager 1992). Roto-tags, freeze-
brands, and radio transmitters (and subsequent transmitter hole marks)
provided reliable means of photographic recognition for those 35 dolphins
which had been freeze-branded in July 1992. While radio-tracking was only
possible for a part of summer 1992, the naturally and artificially marked
dolphins of the area provided a long-term data source by photographic
recognition.

A dolphin group was defined as one or more individuals exhibiting the
same behavioral state(s) in the same geographical area (sometimes up to a
one to two hundred m^ area, probably within acoustic commurucation range),
usually following a 10-m chain rule. Total number of individuals including
neonates and other calves were recorded. Neonates were recognized by fetal
folds and uncoordinated surfacing behavior. Non-neonate calves were
recognized by their small size (generally a body length < 0.75 that of
accompanying adults).

Information was gathered on the broad behavioral categories "traveling",
"feeding", "feeding behind shrimpboat" (FBS), "socializing", "milling",
"bowriding", and "unknown" (and all combinations). Traveling was
indicated by steady movement in one direction. Feeding was indicated by
behavior oriented towards visible fish, such as chasing or tossing them in the
air. Feeding also was suggested by repeated long dives in one location,
without seeing fish, though this was often in the presence of feeding seabirds.
FBS was indicated by dolphins following a trawling shrimpboat, or feeding on
discarded bycatch (Fertl 1994). Socializing was active behavior, indicated by
leaps, breaches, and other aerial behavior; sexual, play, or aggressive behavior;
and much body contact at the surface. Milling was indicated by low activity
levels and lacked components of the above behaviors. Dolphin behavior was
evaluated in the few minutes while approaching the group and/or while
taking photos.

As part of the health evaluation of captured dolphins, a wedge biopsy of
approximately 1 gram of tissue was taken from the dolphin's left flank,
approximately 10 cm posterior to, and 10 cm below, the posterior base of the
dorsal fin (Sweeney 1992). From photogrammetry, we estimated the shallow,
oval shaped biopsies to have been approximately 30 mm long by 20 mm high,
though the dimensions varied by several mm among individuals. Healing of
biopsy wounds was monitored for the periods of July 1992-December 1993,
from photographs of biopsy wounds taken opportunistically during the
regular photographic surveys.

Data Analysis

Dorsal fin photographs were categorized by distinctive features such as
size, location and position of major notches, as well as by artificially-applied
marks (Wiirsig and Jefferson 1990). Sighting locations were plotted and
examined for patterns of range and site fidelity.

Indices of association were calculated for freeze-branded dolphins or\ly by
use of the half-weight index of association (Dice 1945, Cairns and Schwager
1987):

ab

}i(N^^N^)

where

l^^ = the number of times individuals a and b were seen
together,

^^ = the number of times individual a was seen, and
^^ = the number of times individual b was seen.

The half-weight index was chosen because it is commonly used, facilitating
comparison with other studies; and because it is least biased when
individuals of a pair are more likely to be seen separate than together, which
we believed to be a good assumption for the dolphin pairs examined in this
study (Cairns and Schwager 1987).

A minimum of five sightings of an individual was chosen as a criterion
for inclusion in affiliation analyses. We believe that five sightings provide a
reasonable number of resightings from which to generalize, given the small
sample sizes, without limiting the number of individuals so much as to
preclude interesting comparisons. Multiple sightings of an individual in a
single day were counted as a single sighting. Numbers of affiliates were
examined for differences across sex, females with- and without-calf, pregnant
and non-pregnant females (Mann- Whitney U); and age, mean half- weight
index value, range size, mean group size, and number of sightings (simple
linear regression). Mean-index values were compared among dolphins
(Kruskal-Wallis) and between sexes (Mann-Whitney U). We examined an
individual's two "closest" (highest index value) associates for patterns of sex,
age, and reproductive condition.

Behavioral states which involved more thar\ a single behavior were
scored for each behavioral component. Behavioral categories and dolphin
group sizes were examined for variation across each other, survey month,
hour of day (0800-1959), and habitat type ("channel": water bodies such as the
ICW, Big Bayou, and Saluria Bayou; "jetty": between or within 50 m of either
the ICW at Port O'Connor jetties or the Matagorda Ship Channel jetties;
"bay": all other bay waters; and "offshore": gulf waters). For groups containing
freeze-branded dolphins, further analyses were made for differences by sex,
age class, females vsdth- and without-calf, and pregnant and non-pregnant
females. Groups containing more than one category of individual {e.g., males
and females) were scored for each category. Travel directions, in degrees
magnetic, were converted to x-y coordinate vectors and analyzed for
differences between survey month (Watson and Williams test, Batschelet
1972:85). The numbers of neonates seen were examined for seasonal trends.

Differences in geographic distribution were examined by plotting sighting
locations for males vs. females; group size classes of < three, four-six,
and ^ seven dolphins; pregnant vs. non-pregnant females; females with-calf
vs. vsrithout-calf; neonates; behavior (socializing^ traveling, feeding); and age
class.

Estimates of population size were made with Bailey's modification of the
Petersen Estimator. The Petersen Estimator is a ratio which states that the
number of marked animals recaptured in a sample is proportional to the total
number of marked animals in the total population (Blower et al. 1981).
Bailey's modification is an adjustment for recapture v^dth replacement
(Eberhardt et al. 1979, Hammond 1986):

Petersen Estimator Bailey Modification

N = J^ ^^M(n + 1)

where

(min) m + 1

^ = the total papulation size,

1 = the number of animals sampled,

M = the total number of marked animals at large, and

^ = the number of marked animals recaptured (including
resightings of the same individual).

8

Ninety-five percent confidence intervals were calculated from Seber
(1982):

N ± 1.96Vv
where the Bailey-modified variance, v, is

V =

\f\n-¥l)in-m)
(m + l)^(m + 2)

We utilized information from the radio-tracking study to approximate a
dosed population, and thus minimize incorrect assumptions in the
population estimates. Because survey effort was consistent for only a small
portion of the total study area (the region surveyed six times in Fig. 4),
population size estimates were based only on resightings from this 13 km^
area. The number of dolphins estimated to utilize this area was then assumed
to occupy at least the areas of Matagorda and Espiritu Santo bays which lie
within the ranges of the 10 radio-tracked dolphins. Further refinements were
made by determining the total number marked, M, to be not 35, but 17:
sightings of the five calves were not independent of their mothers (except one
sighting in June 1993), and 13 freeze-branded dolphins were considered to be
non-residents in the radio-tracked ranges, based on photo-identification
results.

Slides of biopsy wounds were examined when projected on a screen, or
viewed on a light table with a 8x loupe. Observations were made on the size,
shape, and coloration of the wounds, and compared over time. Calif>er
measurements were made on aspects of the wounds, from projected images.
These relative measurements were then scaled to measurements of dorsal fin
features, the size of which were known from photographs displaying a
measurement scale several cm behind the fin, taken during dolphin capture.
Biopsy wounds were occasionally compared with same-animal radio-tag and
roto-tag wounds. Because the photogrammetric measurements may be
inaccurate by several nron, due to photographic perspective and variation
among individuals, caution should be used in comparison of the
measurements.

For the 36 captured dolphins, the numbers of notches on the posterior
edge of each dorsal fin were counted and compared by sex (Mann-Whitney
U), age, and (for non-calves seen ^ 5 times) number of affiliates (simple linear
regression). Dorsal fin photographs were taken while the captured dolphins
were held for health evaluation. The numbers of notches were counted by
viewdng these slides with a 8x loupe. Or\ly notches which we believed were

large enough to be seen consistently in typical good-quality field-photographs
were counted.

RESULTS

Thirty-six dolphins were captured in July 1992 (biological data from
Sweeney 1992). Animals ranged in age from 2-34 yr. Of non-calves captured,
females had an older mean age and more variability in age than males
(females: x = 19.7 ± 9.34 (SD) yr old, n = 11; males: x = 12.9 ± 4.89 (SD) yr old,
n = 15; f-test P = 0.02). Five mother-calf pairs were caught (three female calves,
two male). Four mothers were pregnant, as were two-three other females. All
pregnant females were in the first trimester. Five males and five females
were radio-tracked. Males ranged in age from 8-19 yr, while females were
from 8 to as old as 31 yr (from tooth aging data supplied by NMFS). One
8-yr-old female (FB505) was pregnant, one 31-yr-old (FB521) was mother to a
2-yr-old calf and pregnant, one 19-yr-old (FB511) was mother to a 1-yr-old calf
and pregnant, and one 12-yT-old (FB515) was mother to a 2-yr-old but
apparently not pregncmt. Appendix 1 summarizes the age and sex
information for all 36 dolphins captured. Appendix 2 provides a summary of
the capture information.

Radio transmissions lasted from a minimum of 13 days (FB505) to a
maximum of 61 days (FB518). The mean was 30.7 days, (SD = 16.85, n = 10)
(Table 1). As is usually the case with radio telemetry, only rarely was the
status of a transmitter or dolphin known when transmissions first ceased.
Several transmitters apparently suffered broken antennas before the packages
fell off. Four dolphins were seen within 5 wk of transmission cessation still
wearing the radios. Radio-tags #4 (FB505) and #5 (FB511), which transmitted
for 13 and 21 days, respectively, were seen on 8 August and 5 August,
respectively, with broken antennas. Some tags which lasted about 3 wk
(FB504, FB522) probably released from the dolphins as planned (FB522 was
seen on 24 August without the radio package). The long-lasting 8-9 wk tags
quit due to either package release or end of battery life. We received a report
of FB501 seen on 23 October still carrying the radio package. FB501 probably
experienced much lower salinities than the others due to the amount of time
she sf>ent in the semi-enclosed San Antonio Bay. As a result, the release
mechanism took longer to corrode than had been calculated. FB518, however,
experienced salinities similar to the other dolphins. Behavioral differences
(e.g., evasiveness, described below) or chance mounting differences may also
account for failure of the packages to release earlier.

When certain radio-tagged dolphins (e.g., FB501, FB505, FB511, FB518)
were approached by boat, they displayed pronounced evasive behaviors,
especially within 2 weeks of radio attachment. This behavior at times resulted

10

in the tagged dolphin temporarily leaving the dolphins with which it was
encountered. Other dolphins {e.g., FB514, FB521, FB522) were not evasive,
however, euid allowed the boat to approach them. Dolphins had become
much less evasive by week 3. However FB501 and FB518 appeared to be
somewhat shy of the vessel throughout their tag attachment time (59 and 61
days, respectively). Most non-radio-tagged, freeze-branded dolphins did not
display such consistent evasiveness when encountered, nor did unhandled
dolphins. This wariness may have been a response to the tag, but there are
few pre-tagging behavioral observations against which to compare. FB501 and
FB518 were not noted to be especially evasive in post radio- tracking sightings.
Of five group sightings of to-be-radio-tagged dolphins in May 1992, only one
group was noted to be evasive of the vessel. In this case, evasiveness was
probably attributable to the group's initial behavior. This group, containing
FB504, was exhibiting "rest" and /or "slow travel". The other four such groups
were "traveling" or "feeding".

All 10 radio-tagged dolphins were morutored in the months after the
radio tracking and have been seen without the packages. Damage to the dorsal
fin varied from small circular scars, to pierced fins, to significant new notches
in the trailing edge, p)erhaps caused by earlier release of the anterior bolt and
subsequent hydrodynamic drag of the radio package.

In addition to the intensive field effort between 6 July and 30 August 1992,
eight other photographic surveys were conducted between 14 May 1992 and 18
June 1993. In total, 136.3 hr were spent on the water, 2,236 dolphins in 648
groups v\rith a mean group size of 3.5 ± 2.86 (SD) dolphii\s were seen, and 4,572
photos were taken (Table 2). Among non-calves, females and males did not
differ in number of sightings (^test), nor was number of sightings linearly
dependent on age (regression). After 12-14 months, freeze-brands became
difficult to read on most adult dolphins; the calf freeze-brands became
unreadable 3-4 months earlier.

Many freeze-branded dolphins were resighted (Fig. 5). Six adults and one
calf whicii were later freeze-branded were identified during the initial survey
in May 1992. Because of the incomplete and sporadic nature of only several
days erf visual surveys during each trip, and the geographically unbalanced
survey effort (Fig. 4), absence of identified animals in the photo-record is not
proof of their absence from the area. On the contrary, the evidence from
resightings indicates a high degree of interseasonal site fidelity. One set of
animals stands out (Fig. 5, FB523-FB532, five males and five females). None
of them were resighted in the year since they were captured and freeze-
branded in July 1992. All were captured at the extreme northeast end of the
study area, 5.5-20 km northeast of the Matagorda Ship Channel Jetties on
Matagorda Peninsula (Appendix 30- Surveys in the year follovdng the

11

summer radio-tracking period did not include that northeast section (see
Fig. 4). However, an amateur's sighting record from November 1992 and data
from an August 1993 survey imply that FB530 periodically visits Saluria
Bayou. Data from August 1993 and November 1993 also contain sightings
along Matagorda Peninsula of FB524 and FB528, respectively. This indicates
that dolphins FB523-FB532 may indeed be resident in Matagorda Bay, but
farther northeast than we usually survey. FB523, hov^ever, was sighted in
May and June 1994, offshore near the Galveston, Texas, jetties (185 km north
of her capture site). We also received a report of a freeze-branded (number
urUcnown) dolphin occurring at the Corpus Christi Ship Channel jetties,
100 km south of Port O'Connor, in November 1992.

In the June 1993 survey, FB503, a pregnant female (still wearing a rototag),
was seen for the first time without her 2-yr-old male calf, FB508. FB503 was
not accompanied by a neonate. FB503's group consisted of FB515 (12-yr-old
female who's calf, FB517, died the previous September) and four other
unidentified dolphins. FB509 (3-yr-old female calf) was also seen v^thout her
pregnant mother, 16-yr-old FB507. Data from a July 1993 survey show that
FB503 was once again seen v^rithout her calf, in a group of eight dolphins
accompanying one of two neonates, and again in August 1993 accompanied by
a calf and one other dolphin. Appendix 3 charts sightings of the non-radio-
tagged dolphins captured.

MOVEMENT PATTERNS

The radio-tagged dolphins had partially to almost completely overlapping
ranges. Mean range size was 140 ± 90.7 (SD) km^ (Table 1). Ranges of radio-
tracked dolphins centered near Port O'Connor in all but three cases (Fig. 6a-c).
The exceptions were FB501, adult female, and FB502, adult male (Fig. 6a); and
FB504, adult male (Fig. 6b). Dolphins FB504 and FB502 sp)ent most of their
time near Port O'Connor and not far from their capture sites, but traversed
20-35 km southwest into western Espiritu Santo Bay and San Antonio Bay on
4 of 21 days and 5-11 of 39 days, respectively (on 5 of the 11 days we located
FB502 in western Espiritu Santo Bay/San Antonio Bay; on the remaining
6 days we could not locate him in the Port O'Connor area and we assume that
he was in the western Espiritu Santo Bay/San Antonio Bay area out of
receiver range, but we did not search there by boat). FB501, however, spent
about one-half of her time (18-45 of 59 days) in San Antonio Bay, often close
to the Aransas National Wildlife Refuge (ANWR). She traveled rapidly
between sites on at least three occasions, and sp>ent time either at the
northeastern (near Port O'Connor) or the southwestern (near ANWR)
pjortion of her range. On one occasion she traveled overnight at least 55 km in
12 hr for a 4.2 km/hr average speed. Because the signal of FB501 (and of all
others over - 20 km distant) could not be picked up by Home Base at Port

12

O'Connor, we often had to search for her by boat, pickup truck, remote station
at ANWR observation tower, or airplane. The other seven dolphins showed
more confined ranges, traveling within a usual radius of about 12 km from
Home Base (Fig. 6b-c). No differences were found in range size by age, sex, or
reproductive condition. A regression of range size on number of days tracked
showed a moderate linear correlation (P = 0.02, R^ = 0.53, n = 10), indicating
that range estimates for some individutds might have benefited from further
tracking. However, range sizes did not change appreciably for most dolphins
past the first week of data collection. In addition, from subsequent photo-
surveys we believe that the duration of the radio-tracking effort was sufficient
to describe the ranges of most of the radio-tagged dolphins.

Dolphins moved between Matagorda and Espiritu Santo bays via the
three linking waterways: the ICW, Big Bayou, and Saluria Bayou (Hg. 1).
Telemetry indicates that dolphins used both the ICW and Steamboat Pass to
move between Espiritu Santo and San Antonio Bays. FB501 used Ayres
Dugout to move between San Antonio and Mesquite Bays (Fig. 6a).

On only three occasions did we obtain evidence of radio-tagged dolphins
leaving the confines of the bay system to swim in the open Gulf of Mexico.
All three positions were v^ithin 1 km offshore of Pass Cavallo, based on signal
strength and bearing. FB518 (11-yr old male) was positioned offshore on
20 July 1992, and FB522 (8-yr old male) on 23 July and 29 July 1992. On 29 July,
FB522 may have been offshore for 6-7 hr, based on the inability to detect a
signal following his initial offshore positioning. Because of errors iriherent in
positioning dolphins by triangulation (as exemplified in Fig. 3) and the
changing influences of habitat structure and climate on signal strength (Mech
1983), movement offshore could in reality have occurred somewhat more or
less often.

Males were found in the extremities of their ranges more often than
females (for horizontal and vertical coordinates P < O.CKK)!, n = 863 male
positions, n = 455 female positions, variance ratio F-test). FB501 was excluded
from this analysis because her "dual home range" movement pattern differed
from that of the other radio-tagged dolphins (see below). Similar results for
random equal subsamples of male and female positions indicate that the
higher male variance is not due simply to larger sample sizes. No differences
in geographic distribution were found for pregnancy, v^dth-calf, or age class,
perhaps due to small sample sizes. No differences in geographic distribution
were found for group size class, behavior, or time of day. That is, mother/ calf
pairs, or feeding dolphins, etc., were not found in particular areas of the study
site.

13

Diumality and week-by-week movement patterns were similar within
and among most dolphins throughout the study (Appendix 4 and 5). The
basic patterns were exemplified by FB518, an 11-yr old male tracked for
61 days. He ranged between the SW portion of Matagorda Bay, from Sand
Point to Pass Cavallo, and NE Espiritu Santo Bay (Fig. 6c). He was never
tracked beyond 13 km from Port O'Connor and ranged v^thin an area
approximately 10 km in diameter, centered at Port O'Connor. There was no
strong shift in movement pattern by time of day (Fig. 7), and he showed no
overall change in movement pattern throughout his 61 -day- tracking jjeriod
(Fig. 8).

FB518 illustrates several general movement patterns seen in the radio-
tracked individuals. (1) Dolphins were capable of, and often did, traverse their
range in several hours. (2) A dolphin traveled widely on some days, perhaps
crossing its range, while on other days movement was very confined, within
1-2 km^. This did not appear to have a temporal or geographic pattern.
(3) Dolphins tended to spend about 1-4 days in a particular portion of their
range. (4) Movement tended to be more confined at night than during
daytime. (5) Dolphins tended to visit the extremes of their ranges orxly in the
daytime. The assertions of (4) and (5) may be biased as a result of less sampling
effort at rught (fewer triangulations and no visual sightings).

The range of FB501 differed from the patterns illustrated by FB518 because
FB501 apparently had 2 main areas of habitat use (near Port O'Connor and
ANWR, respectively) and traveled through the intervening 30 or so km
rapidly. While within one particular area, her movement patterns were
sinular to those of the other radio-tagged dolphins.

SURFACING PATTERNS

A subsample of available radio-telemetered surfacing-interval data gives
an overall x = 33.3 sec mean-dive duration (SD = 5.79, n = 10 dolphins,
508 averaged 30-min samples), surface durations of J = 6.3 sec (SD = 2.16,
n = 10 dolphins, 425 samples), and dive rates of x = 2.0 dives/min (SD = 0.30,
n = 10 dolphins, 507 samples). See Table 3 for a detailed breakdov^m of interval
data. Dive durations did not appear normally distributed; modes and medians
were to the left of means (Fig. 9, P < 0.05, Kolmogorov-Smirnov test for
normality [Zar 1984:92]). Over 50% of dive durations were less than 30 sec,
with maximum dive times reaching over 3 min on rare occasions, and
almost exclusively at night.

Dive durations differed between day and night (but not crepuscular
hours), and across individuals. Night dives, at I = 35.4 sec (SD = 8.43,
n = 9 dolphins, 153 averaged 30-min samples), were significantly longer than

14

the X = 32.4 sec mean dives during daylight hours (SD = 5.94, n = 10 dolphins,
291 30-min samples, P = 0.0006, df = 2, Kruskal-Wallis). The significance of the
test was mostly due to FB504, FB515, FB514, and FB522, which had night dives
longer than day dives by 5-10 sec (Fisher's LSD). Figure 9 shows the difference
between night and day dive durations for actual surfacing intervals rather
than the averaged samples. There was a lower relative frequency of
dives < 10 sec, and higher relative frequency of dives > 50 sec, at night.

The dive durations of individuals were different (P < 0.0001, df = 9,
Kruskal-Wallis). Fisher's LSD revealed that dive durations of FB514 and
FB521 were different from those of most other radio-tagged dolphins. Dives of
FB514 were longer by 6-14 sec, and FB52rs dives were shorter by 8-20 sec.

Mann- Whitney U tests indicated no difference in dive durations between
males and females, pregnant and not-pregnant females, or females with-calf
and without-calf. Dive durations were not linearly dependent on either age or
surface duration.

Dolphins spent more time at the surface between dives at night than i n
the day (P = 0.0053, df = 3, Kruskal-Wallis). Mean nighttime surface duration
was 6.0 sec (SD = 4.8, n = 129 surfacings), mean daytime surface duration was
5.1 sec (SD = 2.92, n = 238). The surface durations of individuals were different
(P < 0.0001, df = 9, Kruskal-Wallis, followed by Fisher's LSD). Fisher's LSD
revealed that FB501, FB505, and FB5irs surface durations differed from those
of almost all other radio-tagged dolphins. FB501 spent 4.5-7.5 sec/surfacing
more at the surface, and FB505 and FB511 spent 3-4.5 sec/surfadng more at
the surface than most other radio-tagged dolphins.

Females spent longer times at the surface than males (P = 0.0278, Mann-
Whitney U), but showed no difference in surface durations between pregnant
and not-pregnant females, or females with-calf and without-calf. Surface
durations were not linearly dependent on age.

Longer night dive and surface durations imply less diving at night. This
is supported statistically by significantly lowner dive rates at night than during
day and crepuscular periods (P = 0.0003, df = 2, Kruskal-Wallis, followed by
Fisher's LSD).

No differences were found in dive rate between sex, pregnant and not
pregnant females, or females with-calf and without-calf (Mann-Whitney U)
or among individuals (Kruskal-Wallis). E>ive rates were not related to age
(simple linear regression). As expected, there was a strong negative relation
between dive rate and dive duration (R'= 0.80, P = 0.0005, ANOVA,
n = 10 dolphins).

15

From boat based observations, surface durations of about 3 sec were
strongly correlated with a single breath. Longer surface durations sometimes
correlated with two breaths, one at the beginning and one at the end of the
surfacing. Occasionally, and especially at night, we recorded surface durations
Icisting many seconds, to > 1 min. Sometimes a dolphin had its transmitter
antenna continuously above water for as long as 3 min. From the tracking
vessel, such protracted surface durations were observed in dolphins
motionless at the surface and in dolphins foraging in very shallow water
(> 0.5 m).

ASSOCIATIONS AMONG INDIVIDUALS

Frequent changes in group sizes and affiliations occurred among these
radio-tagged, freeze-branded, and other recognizable dolphins. Almost all
affiliations for freeze-branded dolphins seen more than once were below
0.200 on the half-weight index of association, indicating that none of the adult
freeze-branded dolphins were dose associates. No difference was found in the
number of affiliates across sex, pregnant vs. non-pregnant,
with-calf vs. without-calf, or age for non-calves with ^ five sightings. Both
male and female dolphins tended to have more male affiliates than female,
and males tended to have more affiliates over-all (for non-calf freeze-branded
aiumals seen ^ five times and with ^ four freeze-branded affiliates). Sample
sizes were insufficient to show potential affiliation differences by age or
reproductive classes.

Affiliations between freeze-branded dolphins only, as judged by
occurrence within the same group in a sighting, were weak except for mother-
calf pairs (Fig. 10). The mean level of association was 0.12 ± 0.027 (SD) (for
non-calves seen ^ five rimes, n = eight males, six females). Table 4 shows the
14 dolphins and their mean index values by sex of affiliate and overall.

Thirty-six of a possible 91 (39%) pairwise combinatioris were sighted. Forty
percent (6/15), 43% (12/28), and 75% (18/24) of pairwrise combinations were
sighted for female-female, male-male, and opposite-sex affiliations,
resp>ecrively. Resighrings of pairs were low: two female-female pairs were
seen twice, one male-male pair was seen twice, cmd six opposite-sex pairs were
seen two to three times.

The mean index value {i.e., level of association) did not differ among
male-male associations, female-female associations, opposite-sex associations,
or associations overall (Kruskal-Wallis, df = 3, P = .45), though male-female
pairs showed greater variability in level of association (Table 5).

16

Mean index value and number of affiliates were not dependent on age
(simple linear regression). However, females with many affiliates had more
male affiliates than females with lower numbers of affiliates (P = 0.007,
R^ = 0.87, simple linear regression) while maintaining a similar number of
female affiliates (P = 0.72, R^ = 0.03). For females, mean index value was not
dependent on number of affiliates (split by sex of affiliate: male P = 0.10,
R2 = 0.67, female P = 0.72, R^ = 0.04).

Males with high numbers of affiliates had more male and female
affiliates. They had lower index values for female affiliates than males with
few affiliates (P = 0.008, R^ = 0.79, simple linear regression), yet showed little
difference in association levels with other males (P = 0.72, R^ = 0.02). Males
sighted in larger mean group sizes tended to have more female affiliates than
those seen in small groups (P = 0.046, R^ = 0.512).

We examined the first and second highest level affiliates ("1°" and
"2°" affiliates, as measured by the tv^o highest association indices) of the eight
male and six female non-calves seen ^ five times (Table 6). Sample sizes were
too small for statistical tests, so we report here on tendencies. One individual
(nnale FB512) had two 1" affiliates (tied index values, a male and a female) and
so was counted twice in some of the following analyses. Eleven of 14 1° and
2° affiliations were of same-sex pairs (7 male-male, 4 female-female). Seven of
eight male-meile 1° and 2* affiliations were of sinular aged dolphins (within
1-3 yr). Four of six 1° and 2° female-female associations were of similar aged
dolphins (within 1-4 yr). Two males and 1 female had 1° affiliates of opposite
sex. Eighteen of 28 affiliations were reciprocated at the 1° or 2° level (i.e., nine
pairs of dolphms). Male-female associations tended to be reciprocated as often
as same-sex affiliations.

The 1" reciprocal male-male pair FB502-FB504 had an index value of 0.190
(Table 6). For FB504 this value was > 2 SD's above his mean index value for
associations with other males, females, or overall (Table 4). For FB502, the
0.190 value was < 1 SD above mean, perhaps due to small sample sizes.
Similarly, the male-male pair FB518-FB522 shared an index value of 0.114
with each other. The index value was > 2 SD above mean for association with
other males for FB518 and for associations overall for FB522. FB518 and FB522
were each others' second highest affiliates (a reciprocal 2° pair). For both
FB518 and FB522, the 1° affiliate was FB521, a female. The FB518-FB521
association was reciprocated at an index value of 0.146, and was approximately
1 SD above the mean for opposite-sex associations, but > 2 SD above mean for
same-sex associations and overall associatiorw, for both individuals. They
were seen more with each other than with other freeze-branded dolphins of
the same sex, respectively.

17

BEHAVIOR

The May 1993 survey was excluded due to its brevity. Behavioral budgets
are biased to an unknown extent by the behavior "feeding behind
shrimpboat" (FBS). The shrimp fishery operates predominantly on summer
mornings to early afternoons in the study area (Spencer Lynn, personal
observation), and trawling shrimpboats are reliable places to find dolphins
(Fertl 1994). Since the primary goal of our field effort subsequent to cessation
of radio-transmitters was to photo-identify individuals, effort was often
biased towards seeking out shrimpboats.

Table 7 presents the proportion of behaviors seen overall and within each
habitat type. Travel represented 50.7% of sightings and feeding 28.4%. Most
behaviors were seen in all habitat types. Travel in "jetty" channels was
common, as was feeding at the ends of jetties and in "channels '.

Dolphins displayed a variety of interesting feeding behaviors, including
individuals "herding" fish against cement walls and ship hulls. Most feeding
appeared to be at an individual level, though aggregations of dolphins
feeding in subgroups of about one to three could be large and spread out over
areas of 100 m^ or more. Several dolphins rapidly converging on one spot
could be evidence of coordinated feeding, or a simple strategy of "getting there
first". Some feeding was seen in very shallow water (> 0.5 m). On one
occasion we observed 4 dolphins "headstanding" in water approximately 1-m
deep. Their bodies and jDedundes were so far in the air that we believe they
may have been rooting in the bottom with their rostrums. Feeding was often
seen concurrently with travel. A typical sighting of travel-feed usually
involved groups of one to three dolphins traveling slowly in a channel.
Individual dolphins would occasionally stop traveling to apparently
investigate habitat structure such as channel walls and ships at dock. Often
evidence of feeding was then seen. Group mates often continued traveling
during the foraging attempt, performing similar activities.

No strong seasonal or hourly trends in behavior or group size were found
(Fig. 11 and Fig. 12, respectively). More groups were encountered traveling in
July-August and September. Trends may be obscured by bias due to FBS in
the May and June surveys, and by spuriously low observations of feeding in
January (n = three feeding observations in January but n = 24 the previous
December). However, from August through December, a trend for increased
sightings of feeding groups is evident. Concomitant with increased feeding is
a trend for decreased social activity from May through January (Fig. 11a).

18

Feeding was common in early mornings but tended to decrease
throughout the day, being replaced by socializing (Fig. lib). There is a curious
increase in "mill" and "unknown" behaviors in mid-day, either of which
may be related to forage, rest, or social activities.

Group sizes were significantly smaller in "channels" (over all habitat
types J = 3.5 ± 2.93 (SD) dolphins /group, for "channel" jc = 3.0 ± 2.54 [SD],
P < 0.0001, ANOVA, followed by Fisher's LSD). Group sizes were skewed
towards smaller groups (median = 2.5, and maximum = 20 dolphins /group
over all groups seen). Group sizes tended to be largest in midday (Fig. 12b) and
for socializing groups (Fig. 13). No difference in group size was found between
age classes, pregnant vs. non-pregnant, vdth-calf vs. without-calf, or sex for
freeze-branded dolphins; however, sizes of groups containing males had
greater variance than did those containing females (with males
J = 7.3 ± 2.25 [SD], n = 8 dolphins; with females x = 6.0 ± 1.40 [SD], n = 8).
Biases in behavioral analyses resulting from unequal representation of
individual dolphins ii\ the data set can be gauged by sighting frequencies
shown in Figure 10.

Travel direction showed a NE/SW bimodality (Table 8, Figiire 14),
probably an artifact of the geography of the study site, which is essentially a
corridor with NE/SW orientation. Analysis of behavior by sex, age, pregnancy
and with-calf was inconclusive, perhaps due to small sample sizes.
Frequencies of behaviors were not significantly different between males and
females (P = 0.06, Mann-Whitney U). Excluding May 1993, of all surveys
between July 1992 and June 1993 (Table 2), neonates were seen only in the
July-August and September 1992; and June 1993 surveys. The proportion of
neonates to other dolphins was x = 0.02 ± 0.028 (SD) (n = 8 surveys).

POPULATION SIZE

Mark/recapture data indicate that of 409 dolphin sightings during surveys
not biased by radio-tracking, there were 31 resightings of freeze-branded
animals. Bailey mark /recapture p)opulation size estimates ranged from 101
(June 1993) to 434 (October 1992) (Table 9). Over all sbc surveys, representing
13 months, the estimate was 218 dolphins. Figure 15 shows the area used for
making "recaptures" (resighings) and the area which the 218 dolphins are
assumed to occupy. As a comparison, "unrefined" estimates, based on Af = 30
with resightings from the entire survey area (all shaded areas in Fig. 4), yield
Bailey estimates of 370 (January 1993) to 1,161 (October 1992).

Our method of approximating geographic population closure gives an
indication of the amount of dolphin use of the area, implying that in a year's

19

time, 218 individual dolphins may utilize the small 13 km^ shaded region of
Figure 15.

HEALING OF BIOPSIES

Biopsy marks of 16 individual dolphins were photographed 1-4 times
post-biopsy, spanning from eight to 476 days elapsed time (Appendix 6)
yielding 27 post-biopsy photographs. Table 10 groups observations from these
27 photos, plus two photos of fresh biopsies, into four stages of wedge biopsy
healing.

Biopsies were approximately 30-mm long by 20-mm wide. A fresh biopsy
app>eared pink to red, oval shaped and several mm deep. Eight to 18 days post-
biopsy, the oval wound was whitish with some pinkish coloration
remaining. The center of the wound was a darker spot measuring 4-5 mm in
diameter. The skin at the edge of some of these stage 1 wounds was darker
than the surrounding normal skin in a 2.7-3.3 mm band. The wound,
including dark band, may also be surrounded by a halo of lighter gray skin,
gradually fading into normally pigmented skin. By days 15-26 post-biopsy
(stage 2) all pink coloration was absent. The central dark spot (3.6 mm
diameter) and light gray halo (3.9 mm band) remained. In stage 3, at
40-42 days, a white spot remained, with no other discoloration. By stage 4
(> 61 days), pigmentation of the wounds was normal or nearly so. An
indentation a few mm deep was still present in the blubber layer of one
individual, FB517, recovered dead (see Appendix 3).

Epidermis appears to have covered the entire wound by day 40 (stage 3)
and at least by day 61 (stage 4), but pxjssibly as early as day eight or 15 (stage 2),
judged by the absence of pinkish coloration and smooth appearance of the
wound. The new epidermal layer, which covers the wound before the
underlying blubber layer is fully filled-in, is repigmented in stage 3.

DORSAL FIN NOTCHES

The number of notches on the trailing edge of a dolphin's dorsal fin was
not different between males and females (P = 069, Mann-Whitney U,
n = 20 males, 16 females). The exclusion of calves did not affect this analysis.
Mean number of notches was 5.9 ± 2.77 (SD) (range 0-10, n = 36 dolphins).
There was a tendency for older males to have more notches than younger
males (P = 0.0014, R^ = 0.44, simple linear regression). This trend was not
noticeable in females (P = 0.12, R^ = 0.16). Females (excluding calves) with
more female freeze-branded affiliates showed a tendency to have more
notches than those with fewer female affiliates (P = 0.06, R^ = 0.61). No trend

20

was evident for the number of male affiliates. For males, number of notches
was not linearly dependent on number of affiliates.

DISCUSSION

Radio transmitter life spans of 13-61 days made possible a detailed
analysis of ranges, individual interactions, diurnal behavior, eind habitat
preferences of 10 bottlenose dolphins in a warm temp>erate inshore ecosystem.
Tracking 10 or nearly 10 dolphins simultaneously resulted in a better overall
capability for analysis of affiliations and overlapping ranges than has been
accomplished for dolphins in the past via radio-tracking. We attribute the
success of the tagging /tracking work to a combination of package design and
to an exf)erienced, dedicated research team in the field. Often in past studies,
tag design, especially of the eintenna attachment; package attachment; or
follow-up tracking were faulty. These problems were minimized for this
work. We recommend that even very small transmitter systems be attached
for not more than 2-3 months, to avoid adverse reaction of the dolphins to
the package, by chafing or otherwise hindering the animals. Antennas and
packages will always be subject to tremendous stresses when dolphii\s leap,
rub along the bottom, or engage in boisterous social-sexual play.

Some radio-tagged dolphins were wary of the research vessels, including
boats which were not present or which had the engines off during capture
and processing. The avoidance was variable; it did not appear dependent on
age, sex, or reproductive status. Evasiveness has been noticed before, reported
as strong in animals with large radio packages (Wiirsig 1982), intermediate
with intermediate "cigarette box" size packages (Norris et al. 1985, 1994), and
variably weak in the present situation. We have no explanation as to why
some dolphins appear to have no adverse behavioral response to tagging
while others seem quite disturbed by it. We also do not know how the tag
may affect normal movement and behavior patterns. However, we observed
all behavioral states, including socializing and bowriding, in radio-carrying
dolphins.

MOVEMENT PATTERNS

The ranges of most dolphins were about 20 km in diameter for seven
animals, and 50 km in diameter for three animals. Ranges overlapped
strongly for all 10 of the radio-tagged dolphins and most of the other freeze-
branded dolphins; except for the 10 individuals caught in the extreme
northeast of the study area, which apparently did not frequent the Port
O'Connor area or eastern Espiritu Santo Bay.

21

While reports of residency are ubiquitous in the literature, measurements
of geographic area commonly used by individuals are rarer. Researchers at
two study sites have provided precise estimates of dolphin ranges. On the
California coast, individual dolphins commonly range over > 50-483 km of
coastline (Defran et al. in press) in a 0.5-km-v^ide strip (Hansen and Defran
1989). Following a 1982 El Nifto-related range extension, some individuals
have been seen to make a 1,340 km round- trip from Sam Diego to Monterey
over about 70 days (Wells et al. 1990). Hansen (1983) considered some
dolphins to be resident to the 155-km strip around his La JoUa study site
during his 17 month study. Nine individuals have been consistently
resighted in Monterey through 1993 "suggesting a degree of site fidelity not
previously documented for Pacific coast bottlenose dolphins" (Scott et al.
1993). Range boundaries may be delineated by depth or distance from shore
(offshore boundary, Weller 1991), temperature (northern boundary. Wells et
al. 1990), and physical or hydrographic features (southern boundary, Caldwell
et al. 1991). No seasonal movement patten\s have been found (Hansen 1990).
Hansen (1990) notes that range boundaries delineated by topographic featvu-es
"are not inviolate and may in fact just correlate with preferred areas".

On the Florida gulf coast, the population is hypothesized to be structiired
into geographically adjacent "communities" with some social mixing and
geographic overlap (see summaries in Scott et al. 1990a, Wells 1991). The
Sarasota Bay area community consists of approximately 100 individuals,
ranging over 100 km^ to about 1 km offshore (Wells 1991). Range boundaries
seem to be delineated by water depth (Wells et al. 1987). Individuals in
different age and sex classes have different sized "core use areas" which seem
to be on the order of 50-100 km^ (Wells 1991). Within the community home
range, individuals show tendencies for seasonal habitat use patterns probably
related to prey and predator movements (Irvine et al. 1981).

In the present study, radio-tagged dolphins had two distinct range areas
(Fig. 6). This is consistent with Gruber's (1981) hypothesized "extended herd
home ranges" with shared borders in the Port O'Cormor area. For example,
FB515 stayed mainly in the NE section of Espiritu Santo Bay and FB514 in an
adjoining area in SW Matagorda Bay (Fig. 6c). Both were originally captured
together in the small overlapping area. Ranges for FB518, FB521, FB511, and
FB522 all overlap strongly. These dolphins were caught together (FB518,
FB521) or in areas only 4 km apart (FB511, FB522). A third "extended herd
home range" to the northwest along Matagorda Peninsula is suggested by the
lack of resigh tings of 10 of the 11 individuals captxired there (Appendix 3f).
These 10 were not seen in the following year, perhaps due to lade of effort
northwest of our primary study area; data from later surveys indicate that
some of them may have been present, as discussed below. The 11th dolphin,
FB522 (radio-tag #10), seldom frequented that area in the remainder of his

22

radio's life span. The hypothesized "extended herd honne range" boundaries
in this study correspond well with those of Gruber (1981:52). Individually
preferred areas were also hypothesized by Shane (1977) and Price-May (1993)
for the Port Aransas, Texas area.

Bottlenose dolphins in Matagorda Bay show intriguing parallels to the
Sarasota Bay connmunity. The mean 140 ± 90.7 (SD) km^ range size for
individuals in the present study is similar to ranges in the Sarasota area. The
Sarasota community is composed, in part, of several "bands" of females and
their calves. Some bands contain more than one matriline. In the Matagorda
Bay area, evidence of several "extended herd home ranges" within at least 312
km^ overlapping near Port O'Connor, could correspond to the adjacent
communities hypothesized to reside along the Florida west coast, or to the
matrilineal bands seen within the Sarasota dolphin community. Dolphin
movement ranges in Matagorda, as revealed by radio-tracking, appeared very
similar to early radio-tracking results in Sarasota Bay (Irvine et al. 1981). In
both studies, individual dolphins used separate but somewhat overlapping
regions of the bays, and individual ranges were on the order of 100 km^. The
radio-tracked ranges in Irvine et al. (1981) for Sarasota Bay corresponded
generally to what, with more data, came to be recognized as female band
ranges, shown in Wells (1991). Wells et al. (1993) reported a "mosaic of
overlapping home ranges" for individuals in Sarasota and neighboring
communities.

A "dual home range", similar to that of FB501, was described by Caldwell
and Caldwell (1972:64) for an albino bottlenose dolphin known from Saint
Helena Sound, South Carolina (Essapian 1962) and Georgia waters, a
minimum 60-km-traveling range.

Shane (1977), Gruber (1981), and McHugh (1989) report very limited
movement in either direction through passes linking Texas bays with the
Gulf of Mexico. Wiirsig (unpublished data) indicates that this type of
movement by "resident" dolphins may be more frequent for Galveston Bay.
Data from the present study suggest that such movement by these apparently
resident dolphins does occur, but infrequently, lasting on the order of several
hours, and to an unknown distance offshore (but probably within a few
kilometers). The radio tracked dolphins of the present study were not
observed to leave the bay system to feed (for example) in oceanic waters. This
is an imjX)rtant finding, for it indicates that — if true for a large part of the
inshore animals — these dolphins are potentially susceptible to localized toxin
input from agricultural runoff or industry. If ongoing studies indicate that the
35 freeze-branded dolphins have long-term (across year) site fidelity for all
activities, including feeding, this potential habitat influence may be judged to
be even greater.

23

Dolphins in Matagorda Bay (but not necessarily other Texas bays) may
show less offshore movement than in Sarasota, Florida, where the
community home range is considered to extend 1 km offshore. Dolphins in
the Indian/ Banana River system on the Florida east coast showed no
movement offshore in surveys conducted between August 1979 and October
1981 (Odell and Asper 1990).

There was a greater geographic spread of male dolphin sightings (variance
ratio F-test). If we assume capture and sampling biases were small between
the sexes, this pattern might arise from two different behavioral traits:

(1) males have larger ranges than females (not supported statistically) or

(2) range sizes are similar for both sexes but males visit more of their range
more frequently or for longer periods, and are therefore more likely to be
found in a wider distribution. Male dolphins in Sarasota Bay have shown
both traits (Wells et al. 1987, Wells 1991). The "resident male pattern" was
typified by lone males associating frequently with females and remaining i n
the relatively limited area within which females ranged. The "roving male
pattern" was characterized by males who roamed throughout the community
home range. The "resident males " were seen with reproductively receptive
females more than the "roving males" (Wells et al. 1987). It is possible that
the patterns have to do with sexual maturity and obtaining mating
opportunities.

We believe that most of the marked dolphins were resident to the area
during the major study, and sporadic sightings throughout the year and from
unanalyzed surveys through August 1994 indicated longer term residency as
well. However, a bias may exist if the 35 marked animals were not collected at
random from the jX)pulation. Certain biases were inherent in the dolphin
capture procedures. All amimals were caught in or very near water shallow
enough for humans to stand, a requisite for the surround-net capture method
(Asper 1975). For dolphin and human safety, the capture effort avoided
dolphin groups of greater than five individuals and grouf>s containing
dolphins less than one year old (Sweeney 1992). It is possible that these
shallow-water dolphins displayed more site fidelity than dolphins fotmd in
deeper waters of the bay, and that interchange with other bay systems and
with the open ocean may be greater than indicated by this subsample. Such
biases may also explain why we apparently captvired older females than
males.

Coastal bottlenose dolphins appear to have "home ranges". Range size
and dolphin movement patterns have been hypothesized to be dependent
upon reproductive (Scott et al. 1990a) and/or forage (Scott et al. 1990a, Weller
1991, Balance 1992, Bearzi and Notarbartolo di Sciara 1993) resources. All
coastal studies using some form of individual identification show resighting

24

of individual dolphins (e.g., Shane 1977, Wiirsig and Wiirsig 1977, Acevedo-
Guti^rrez 1989, Harzen 1989, Peddemors 1989, Ballance 1990, Bel'kovich 1991,
Delgado 1991, Rudin et al. 1991, Wells 1991, Smolker et al. 1992, Bearzi and
Notarbartolo di Sciara 1993, Curran et al. 1993, Mallon-Day 1993, Swingle et al.
1993, Brager et al. 1994, the present study, Defran et al. in press). Across
studies, there is variation in resighting rate, which seems to correlate with
range size where such information is available {e.g., Weller 1991, Wells 1991,
the present study). For most study sites, one cannot yet conclude "lifetime"
residency, and there will always be differences among individuals, but many
sites show residency over several years {e.g., Golfo San Jos6, Argentina
[Wiirsig and Harris 1990]; Sarasota Bay, Florida [Scott et al. 1990a]; California
coast [Weller 1991]; and Shark Bay, Western Australia [Smolker et al. 1992]. In
Texas, resightings for a few well known individuals have spanned 6 yr
(Galveston Bay, Fertl 1993) and 15 yr (Aransas Pass, L. Price-May personal
commuTucation). Our results indicate that long-term residency may be a habit
of many within-bay bottlenose dolphins on the Texas coast.

Although dolphins were not radio-tracked out of the study area south of
the Aransas National Wildlife Refuge, we received a report of a freeze-
branded (number unknovm) dolphin occurring at the Corpus Christi Ship
Channel jetties, 100 km south of Port O'Connor, in November 1992. Other
evidence of occasional long-distance movements along Texas comes from
several sources. Gruber (1981) describes a Matagorda Bay sighting of a dolphin
originally identified by Shane (1977) in the Corpus Christi area. Jones (1991)
describes two dolphins that were resighted at Gulf inlets 517 km and 622 km
from where they were initially identified. Jones (1991) found that 11 of 146
identified dolphins occurred at two or more inlets, and all but the above two
long-distance movements were of distances < 300 km. The May 1992 and May
1993 Matagorda Bay surveys yielded identifications of two dolphins that had
been previously seen in the South Padre Island area, 285 km south (Wiirsig
unpublished data). Finally, FB523 was photographically documented in
Galveston waters in May 1994. At present there is little information on how
the long-range movement exhibited by some dolphins interleaves with
possible long-term residency to relatively small geographic ranges of other
individuals.

In Califonua, such long distance movements seem common (Defran and
Weller 1993). Similar long distance movements are reported sporadically
from other areas as well. Dolphins in the Moray Firth, Scotland, are known to
travel 225 km (Currim et al. 93). Dolphins in Ciolfo San Jos^, Argentina, were
seen to travel 600 km round-trip (Wiirsig 1978). The sporadic nature of these
reports may be due to lack of effort more than rarity of long-distance
movement.

25

On the southeast US coast, nearshore bottlenose dolphins migrate
seasonally (Kenney 1990). They travel northward in the summer as far as
Delaware Bay, New Jersey, and southward in the winter, where they range
into Florida (Mead and Potter 1990, Mallon-Day 1993). Seasonal density
changes have been found in Texas bays, cis discussed below, but nothing is yet
known about the source of the arriving dolphins or the destination of those
departing. It is not known whether migration is inshore between bays,
coastally longshore, or directly offshore.

SURFACING PATTERNS

Mean dive duratiorxs on the order of 20-40 sec, as we have found, are
common in coastal bottlenose dolphins (e.g., Shane 1977, 1990, Wiirsig 1978,
Ballance 1992). Though occasional radio-telemetered dives may be spuriously
long (dolphins were seen to surface for a breath without expxjsing enough
antenna for a signal to be received) maximum dive durations of around 3
min have also been observed in Sado Estuary, Portugal (dos Santos and
Lacerda 1987). Several studies have shown different dive durations and
surfacing patterns to correlate with different behaviors (Shane 1977, 1990,
Ballance 1992). We hop)e that further analyses of the surfacing interval data by
members of the MMRP will provide a link between surface duration and
number of respirations, and an eventual ability to ascertain general behavior
by a description of remotely-sensed telemetry information when correlated
with the behavioral observations made by the tracking vessel.

We found longer dives during night than in the day. Long night-time
dives by dolphirxs living near or beyond continental shelf waters often signify
increased feeding (Wiirsig and Wiirsig 1979, 1980; Norris et al. 1985). In the
present study, a difference of only a few seconds would seem to be of little
biological significemce. However, the data are means of means, which tends to
reduce variability; and, taken together with longer surface durations and
lower dive rates at night, we believe that longer average nighttime dives may
be related to resting. While no evidence of a diurnal difference was reported
for radio-tagged dolphins in Sarasota Bay, Florida by Irvine et al. (1981),
Rossbach et al. (1993) found longer dives and more time submerged in the
afternoon /evening than in early morning for one satellite tagged individual
in Tampa Bay, Florida.

Some long dives were interspersed with protracted surface times (many
seconds, to minutes). These tended to occur more frequently at night, but we
also have observed protracted surface durations exhibited by dolphins resting,
or feeding or traveling in extremely shallow water (< 0.5 m deep) in the
daytime. Irvine et al. (1981) also report that dolphins stayed at the surface for
minutes at a time in the Sarasota area. We recorded longer mean surface

26

durations in some individuals. If the longer durations are due to more
protracted times at the surface, then this could indicate that individuals differ
in their resting and /or feeding behavior.

ASSOCIATIONS AMONG INDIVIDUALS

While the association index values did not show many differences
between males and females, among freeze-branded dolphins; males with
many affiliates tended to have higher numbers of both male and female
affiliates and to spend less time with females than males with few freeze-
branded affiliates. At a low level, some females {e.g., FB515, FB521) associated
vdth many freeze-branded males, and some males {e.g., FB504, FB518, FB538)
associated with many freeze-branded females (Table 4, Fig. 10).

Dolphins showed intriguing commonalities with their two highest level
associates. A dolphin and its V and 2° affiliates tended to be of similar age,
especially for males. Eleven of 14 T and 2° affiliates were of same sex pairs.
Some affiliations were greater than one and two SD above mean index
values. Several studies have considered affiliations > 1 SD above mean to be
"significant", using that level to establish sodobiologically important
groupings of individuals (Heimlich-Boran 1986, 1993, Wells et al. 1987,
Weller 1991). However, values < 0.2 are generally not considered biologically
significant {e.g., Weller 1991, Smolker et al. 1992).

Brager et al. (1994) found mean index values of 0.125 among affiliatioris of
35 naturally marked dolphins in the Galveston Bay, Texas, area in 1991.
Approximately 63% of 595 possible pairwise combinations were not seen.
Approximately 70% of the sighted pairs had index values between 0.001 and
0.190, 23% between 0.200 and 0.390, and an additional 7% between 0.400 and 1
on the half-weight index. Some high level associations were apparently stable
over at least 19 months.

Wells et al. (1987) and Wells (1991) report moderate index values
{e.g., 0.310, 0.560) among "female band" members, values in the 0.450-0.750
range for "strongly bonded" adult males, and values of 0.080-0.100 (0.150
considered high) for male-female affiliations in Sarasota Bay, Florida. The
majority of sighted pairwise combinations were between 0.010 and 0.200, and
the average number of affiliates was 60.5 (Wells et al. 1987). Some high-level
same-sex associations have been seen to be stable {i.e., high index values
remained high) at least 10 yr (Wells 1991). Variation was found in association
patterns with age/sexual-maturity for males and females.

In Shark Bay, Western Australia, Smolker et al. (1992) report that
approximately 80% of p)ossible pairwise combinations were between 0 and

27

0.200. While it is unclear what percentage of affiliations were > 0 and < 0.200,
Smolker et al. (1992) describe the 0-0.200 range as indicative of inconsistent
associations. Index levels of approximately 0.210-0.400 were found for female-
female affiliates in general. Values of approximately 0.510 were found for
high-level female-female affiliates ("cliques")- Index values for male affiliates
were spread between 0.210-1. Index values for males forming "male
alliances" were 0.800-1 (Connor et al. 1992). Male-female affiliations were
generally in the 0.210-0.400 range. Some high level associations have been
stable for at least 5 years. Differences were found in the association patterns of
males and females. Smolker et al. (1992) did not use sightings of single
dolphins (or feeding dolphins) in computing their index values. This will
tend to lower the index's denominator (see Methods) and so raise the values,
relative to other studies.

A six year study in the San Diego, California area (Weller 1991, Defran
and Weller in press) lacked the frequent long-term high level associations
seen in Sarasota and Shark bays. A relatively small number of possible
pairwise combinations were not seen. For 160 dolphins, only 38% of possible
pairwise combinations fell between 0 and 0.090. Thirty-three percent fell
between 0.100 and 0.190. Seventy-one percent of all possible pairwise
combinations were below the 0.190 index level. Mean index values for all
affiliations for individuals ranged from 0.135 to 0.299, with the majority of
mean index values from 0.177-0.239. Dolphins tended to associate with many
of the dolphins in the population; number of affiliates increased with
number of sightings (to 259 of 373 identified dolphins for one dolphin by the
end of the study). Some relatively high-level but short-term affiliations were
seen. Associations with index values of around 0.500 were estimated to have
durations of 1-48 months minimum for 20 of 40 reciprocal 1° affiliates. Low
resighting rates (66% of identified dolphins seen about once per year)
contribute to uncertainty about strength and duration of affiliations.

In all of the above studies, many pair combinations have low, but non-
zero index values, indicating that for coastal populations of bottlenose
dolphins, most individuals have probably "met" each other. Unseen pair
combinations (those with index value = 0) may actually occur, but at
undetected levels. In Galveston, where the percent of unseen pairs was
relatively high, the number of possible pairs not seen dropped from about
72% in 1990 to about 63% in 1991. Mean index value for sighted pairs fell from
0.154 to 0.125 "probably from additional low-level associations being
discovered" (Brager et al. 1994). In all studies, the number of low-level
associations (those between 0-0.200) has been on the order of 70% of all
possible pairs (approximately 100% in the present study).

28

While average index values for Matagorda Bay dolphins
(I = 0.119 ± 0.027 [SD]) were similar to overall average values in other
studies, the moderate and high values seen in Galveston, Sarasota, Shark Bay,
and San Diego for some non-mother /calf pairs and differences in these
values with age and sex were absent. By looking only at freeze-branded
dolphins, caught nearly at random with respect to each other, the present
study has examined affiliations between what constitutes a nearly random
sample of the local dolphin population. Other studies, however, have
examined indices of association among the subgroup of dolphins with the
highest sighting rates (e.g., all dolphins seen ^ five times). This latter method
is more likely to discover high-level associates since such pairs of individuals
v^rill have similar sighting frequencies, as they are often seen in the same
group. Clearly, close and long-term associations (indicated by coi\sistent high
index values) are not lacking among Matagorda Bay dolphins. Gruber (1981)
documented several, as did Shane (1977) in Aransas Bay, and Fertl (1994) and
Brager et al. (1994) in Galveston Bay. While we are unable to determine how
our examination of patterns among freeze-branded dolphins only has
influenced these results, we suspect that as data from naturally-marked
individuals is incorporated, Matagorda Bay, which already shares
characteristics of its habitat v^nth Sarasota Bay and other sheltered estuarine
study sites, will be seen to share life history characteristics of its dolphins as
well.

Group composition was not static. Some individuals had as many as
10-13 freeze-branded affiliates over the course of the year. All but four non-
calves sighted ^ five times had > five freeze-branded affiliates, cmd a high
percentage of potential pairv^se combinations was seen. The low association
indices, high numbers of affiliates, and variable group sizes reveal a fluid
sodal structure for these resident dolphins. Confirmation of tendencies
awaits results from naturally marked individuals. Dolphins of the
Matagorda/Espiritu Santo/San Antonio Bay complex probably know each
other well, and often feed and socialize together. They may easily share
tainted prey, disease vectors, or exposure to anthropogenic toxins and
contaminants which could contribute to massive die-offs similar to that
which occurred in Spring 1992. Similarly, parasite occurrence may be quite
equally distributed among adults of the area.

BEHAVIOR

Other studies on the Texas coast consistently indicated high levels of
feeding in the morning, high levels of socializing in the afternoon, and more
time spent feeding with less socializing traveling in winter months (Shane
1977, Gruber 1981, Brager 1993). Increased feeding in colder seasons was
hypothesized to offset increased thermoregulatory demands (Brager 1993) or

29

to reflect increased foraging due to decreased prey availability (Gruber 1981,
Brager 1993). Radio-telemetry in the present study indicated lower activity
levels at night. However, low activity levels at night is not a rule for dolphins
in Matagorda; FB503 was tracked overnight and traveled 55 km in 12 hr.

Sampling biases in the present study may have contributed to weak
patterns. While photo-identification surveys of this type are not a substitute
for behavioral studies, our results from Matagorda do fit patterns for both
seasonal and hourly behaviors seen in other Texas studies, and in other
coastal studies as well {e.g., Shane 1990, Rudin et al. 1991, Bearzi and
Notarbartolo di Sciara 1993). Feeding, often done individually or in small
groups {e.g., two-five dolphins), usually takes up a large proportion of the
day, especially in the morning. Group sizes tend to be larger for socializing
groups (on the order of 5-15 dolphins). Social behavior tends to occur after
feeding in mid-day or evening. Travel may be extensive on less productive
coastlines (Wiirsig and Wiirsig 1979, Ballance 1992).

Waples et al. (1993), in Sarasota Bay, Florida, identified six habitat types
and found, as did we, that the majority of travel occurred in channels and the
majority of milling occurred in bays. They found the majority of feeding to
occur in shallow bay waters. We found the majority of feeding to occur in
channels, but, while we did not examine depth as a habitat characteristic, the
majority of observed feeding in bays occurred in shallow water near shore. In
the present study, channels had a higher proportion of sightings than bays,
but this may reflect "sightability" or effort rather than a habitat preference.
However, except for FBS, feeding occurred more often in channels than in
bays. The additional habitat structure inherent in channels and jetties may
support more prey. In our study site, most channels and jetties are also deeper
than the bays and so concentrate prey in colder weather.

The summer peak in neonate sightings concurs well with pregnancy data
from dolphins caught in July 1992 (all first trimester, n = six), and with a
spring peak derived from stranding data for the entire Texas coast (Fernandez
1992). Most studies report low levels of neonate sightings throughout the
year, with peaks during spring/summer or summer/fall. Data combined from
captive and free-ranging bottlenose dolphins in the northern hemisphere
showed a trend for births to be earlier in the year and have less variability in
timing with increasing latitude (Urian et al. 1993).

POPULATION SIZE

The population estimates (Table 9) do not show a clear sinusoidal
seasonal change. Any such patterns may be masked by the large confidence
intervals or by extrapolating over large areas, as we have. Yet, encounter rates

30

(#Dolphins seen/#Hours on water, Table 2) and the October estimate, indicate
an autumn increase in the number of dolphins in the Port O'Connor area.
Gruber (1981), in the Port O'Connor area, and Shane (1977) and McHugh
(1989) in the Aransas Pass area 100 km south, found fall /winter increases and
spring/summer decreases in dolphin numbers. Jones (1988), in the Galveston
area, 200 km north of Matagorda, found higher autumn numbers. These
changing abundances may be attributable to low level, short range migratory
movements to warmer waters (Jones 1988) or to a reaction to changing prey
densities (Gruber 1981). Further radio-tracking and photographic
identification studies are necessary to elucidate subtleties in and sources of
seasonal patterns.

Gruber's (1981) population estimates for the 75 km^ area surrounding Port
O'Connor ranged from 93.4 ± 5.39 (SD) dolphins (1.2 dolphins/km^) in winter
to 48.6 ± 19.25 (SD) dolphins (0.6 dolphins/km^) in spring, from boat-based
subarea counts. Our estimated papulation is assumed to range over 312 km^,
yielding similar densities. Note, however, that dolphins are not uniformly
distributed over the area but tire found more frequently near shorelines and
channels. Sarasota Bay also has densities on the order of one dolphin /km^,
and is a very similar barrier island /estuarine habitat.

We do not know if the study area (shaded areas of Fig. 4) represents an
area enclosing most of a breeding population. We assume not, since
10 dolphins tagged in the northeast of this area were never resighted in the
area, and were presumably resident further northeast in Matagorda Bay. As
well, the extended ranges of some individuals and infrequent sightings of
recognizable dolphins in other than their core areas (e.g., Jones 1991), argue
against group isolation.

HEALING OF BIOPSIES

We saw no obvious signs of infection in either biopsy or tag wounds. As a
rule, the radio-tag (and probably rototag) wounds healed slower than the
biopsy wounds, though it is evident that healing of the three wound types
went through similar stages (Appendix 6). The radio-tag and rototag wounds
differed from wedge biopsies in several ways. Radio-tags and roto-tags are
piercings involving foreign material passing through and pressing against
skin and connective tissue of the dorsal fin, not blubber, for several weeks'
duration. Scott et al. (1990:508) note that "tags that break the skin can wick
bacteria into the wound and prevent it from healing". Hindered cleansing of
the tag wounds may contribute to slower healing rates as well.

Bruce-Allen and Geraci (1985) report on a controlled study of
morphology, hematology, and ultrastructure of healing of 2 mm deep scalpel

31

cuts in captive bottlenose dolphins. They examined the wounds at 1, 3, 7, and
10 days. While Bruce- Allen and Geraci examined very shallow lacerations in
captive animals over a short period of time, some interesting morphological
parallels to the present study are apparent.

After 6 hr the wounds studied by Bruce-Allen and Gerad had "raised,
sharp black edges". By day 1 the dark lines were more pronounced. In the
present study, the darker skin surrounding the wound seen in stages 1 and 2
(Table 10) may correspond to the darker skin seen by Bruce- Allen and Gerad
through at least day 2. By day 3 of the Bruce- Allen and Gerad study, a thin,
poorly pigmented epidermal layer had completely covered the experimental
laceration. The larger and deeper biopsy wounds of the present study's free-
ranging dolphins may have been covered by new epidermis as early as day 15.
On day 7 of the Bruce-Allen and Geraci study, the epidernus was well healed,
but the lacerations were white in color and "a .5 cm medium gray halo
remained, blending into the surrounding tissue". We observed a similar gray
halo in stages 1 and 2 (days 8 to 26), measuring approximately 4 mm wide. On
day 10 of the Bruce-Allen and Gerad study, wounds were becoming
repigmented and the lacerations were visible as a "white linear mark
bordered by a narrow dark gray band". In the present study, the entire surface
area of the wounds was repigmented by day 61.

Bruce-Allen and Gerad concluded that healing in bottlenose dolphins
was not dramatically different from that of terrestrial mammals, undergoing
similar histological and ultrastructural stages and that, at least for cutaneous
wounds, healing occurred at rates similar to terrestrial mammals. The lack of
color was assodated with "pale, unaligned spinous cells with diffuse [not
perinuclear] melanosomes" (Bruce-Allen and Gerad 1985). One point of
departure from healing in terrestrial mammals was noted by Bruce-Allen and
Geraci. They found no scab, but instead a transformation of exposed
epidermal surface to degenerating cells with vesicles. They hypothesized that
this served as a buffer between the saltwater environment and healing tissue.

Sample size limitations precluded comparisons within and among
individuals; and across sex, age, health, and reproductive condition classes. It
is interesting to note, however, that the dolphin which received the poorest
heath evaluation, FB517, provided the earliest datapoint in the final healing
stage of Table 10 (61 days post biopsy). Poor health may not hamper healing of
deep wounds to the blubber layer.

Behavioral responses of the dolphins were monitored during the
physiological processing, which involved bringing the dolphins aboard a boat
(Sweeney 1992). The responses were generally calm, but some animals became
agitated enough that processing stopped early or was finished in the water

32

(Sweeney 1992). Due to the amount of handling the dolphins received
additional to the biopsies, it was impossible to interpret behavioral reactions
to the biopsies alone.

DORSAL FIN NOTCHES

Our data indicate that a dolphin's notching pattern may change over
time. While this conclusion should come as no surprise to others applying
similar methods of photo-identification (notch accumulation over time by
individuals has been mentioned by Scott et al. [1990] and Wiirsig and Harris
[1990]), it would be imprecise to conclude from our data that all dolphins are
bom with no notches and steadily accumulate them throughout life. These
data represent a "snapshot" of 36 different dolphins, not a longitudinal study.
Male dolphins could, for instance, accumulate the majority of their notches as
juveniles, while assimilating themselves into the social system. The tendency
for female dolphins to have more notches with increasing numbers of female
affiliates implies that some notching may occur as a result of social
interactions.

CONCLUSIONS

The Texas coast, spanning 2.5° latitude, with its unique cycling of tropical
and temperate conditions and sparse coastal beaches punctuated by
productive estuaries, presents an interesting yet little understood blend of
bottlenose dolphin life history patterns. Bottlenose dolphins on the Texas
coast have movement and social patterns similar to those of other coastal
bottlenose dolphir\s, yet the pattenis are not simply a duplication of findings
from other, better understood study sites.

With resp)ect to mass mortalities, the Matagorda Bay dolphin population
seems to be physically healthy (Sweeney 1992) and numerically robust,
occupying all surveyed regions of the bay. The resident dolphins are probably
susceptible to local anthropogenic cmd naturally occurring toxins. Post-1992
die-off population numbers appear not to have changed from earlier
estimates (Gruber 1981). However, statistical power to detect a decrease in
numbers between this and previous studies is probably low, given the erratic
survey effort and large confidence intervals. The handful of exeimples of
travel between Texas bays, in spite of the low level monitoring effort which
produced the observations, suggests to us that an individual Texas bay
ecosystem could recover numerically from localized dolphin mortalities.
These regional, within bay, dolphin populations do not appear to be truly
isolated.

33

These conclusions must be considered tentative, however. Despite the
indicated non-isolated nature of the population, nothing is yet known about
interactions between the apparently resident dolphins and the visitors, and it
is not known if the dolphins which died in spring 1992 were resident. If the
resident dolphins seldom mate with visitors, loss of all or most residents in
an area could have significant impact on the genetic (and perhaps cultural)
makeup of dolphins in the area regardless of numeric recovery. This study
raises several questions: Are there separate inshore/resident and
coastal/ transient bottlenose dolphin stocks on the Texas coast? If so, is there
genetic exchange? What sociobiological factors drive the two lifestyles, and
would an otherwise non-resident dolphin take up residenc}' in a depleted
bay?

The major ambiguities of population extent and size, social and
behavioral patterns, and characterizations of within-bay vs. gulf-coast
dolphins can only be answered by further work. We recommend:
(1) continued visual and photographic survey efforts, on a monthly basis, to
catalogue and reliably re-identify not only human-marked but naturally
identifiable dolphins throughout this and other Texas bay systems and along
the Texas gulf coast; (2) an intensive genetic study along the entire Texas
coast, to coordinate with the ongoing MMRP photo-identification work in the
bay systems of Galveston, Matagorda, Corpus Christi, and South Padre Island;
and (3) at least two more intensive NMFS-led physiology/radio-tracking
efforts to recapture some of the same dolphins for physiology and toxin level
follow-up. The second point is especially necessary for proper description of
population discreteness and size(s), and evaluation of the effects of mass
mortalities. The third recommendation will provide further data on sex and
age distributions, necessary for a fuller understanding of the sociobiology of
dolphins on the Texas coast.

34

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43

iti*

Louisiana

Texas/. .•>>;yV>i^ N^verton Bay
-Matagorda Bay
San Antonio Bay

^Corpus Chriati Bay

Gulf of Mexico

Sand Point

^t^ Maugorda Bay ^

Gulf of Mexico

San Antonio
Bay

Figxire 1 . Map of the Port O'Connor area of Matagorda Bay.

45

b.

Figure 2. Left and right sides of a dolphin dorsal fin (FB502) showing radio
package placement (a) and magnesium nuts (b).

46

Matagorda Bay

Gulf of Mexico

Figure 3. Example triangiilation for FB518 at 1045 hr, 11 August 1992, from
Home Base, in Port O'Connor, and a tracking vessel at the base of the western
Matagorda Ship Chaiuvel jetty. Shaded region indicates tt\e error polygcm
associated with the position of the dolphin. A ± 5° error range is indicated for
five-element antennas.

47

Matagorda Bay

Shading indicates the number
of surveys in which a region
was visited out of 6 surveys
total.

□ Surveyed 0 times.

□ Surveyed 2 times.
E Surveyed 3 times. /

g Surveyed 4 times.
Surveyed 5 times.
■ Surveyed 6 times.

Gulf of Mexico

Figure 4. Photographic survey effort. May 1992-June 1993. Surveys from July
1992-September 1992 are excluded because they are biased for radio tracking.
The May 1993 survey is excluded because it ended early due to inclement
weather.

48

Females and calv««

Dolphin

FB501
mFB503
cFBSOa

FB505
mFB507
cFBSO©
mFBSII
CFB513
mFBSIS
CFB517

FB519
mFB521
CFB520

FB523

FB525

FB527

FB52g

FB531

—

■1

■

■

1

--^

ll

■

^1

■

1

IB

T.

M

1

■■

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■

||H||||

^^^^H

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■ ^^H

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Survey

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g

- |g

s s & •

O -^ 2 2

c

3

- ? ^

>• I

Survey

? s

CM

s

^ o o

■ • * §

Figure 5. Sightings of freeze-branded dolphins across surveys, "m" and "c"
denote mother-calf pairs.

• FB517, calf of FB515, was found dead on 13 September 1992. Necropsy showed
that it died from an intestinal infarction unrelated to captxu^ or tagging stress
(TMMSN 1992).

49

si

• ■

r c

t^ >o w>

QC3*

r^

50

I

6 4/5

&3
■a s
era:

I

to 2.

51

1. H FB514, 19 yrs, n=9i'd"^
QFB515, 12yrs,C, «=i4 9

3. E3 FB518, n yrs, «=225 d
0 FB521, 31 yre, P, QniiZS 9

Rgure 6c. Summary reinges for radio tagged dolphins FB514 and FB515 (1),
FB511 and FB522 (2), and FB518 and FB521 (3), from radio teJenetry and
sightings. May 1992-June 1993, with informatiai on age and sex. T" denotes
a pregnant animal, "C" denotes "with calT. "«" refers to the nimxber of
positions used to determine the ranges.

52

• 23.00- 01 «)n=«
+05«)-08«)n=ll
oil.-00-13«)n=16
m 18.-00 - 2D100 n=10

Gulf of Mexico

Figure 7. Positions of FB518 by time of day, 15 June 1992-13 September 1992,
from radio tdemetry and sightings.

53

Matagorda Bay

Gulf of Mexico

Figure 8. Approximate noon positions for dolphin FB518, 15 June 1992-13
Septen\ber 1992, from radio tracking and sightings (two subsequent sightings
in bold), "n" = 53 positions.

54

.35
.3

i

w

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0*^

Day

Mean

27.9

SD

24.10

n

655

Medan

21

20 40 60

I * I » I — •— 1 — •— 1 — • I • I

80 100 120 140 160 180 200 220 240

Dive Duration (sec)

.35

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t

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TThhm

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27

f=^

» I * I ' I ' I * — I — * — I • I < I — •— T — • I • I — »— T"

0 20 40 60 80 100 120 140 160 180 200 220 240

Dive Duraticn (sec)

Figtire 9. Relative frequency histogrants of dive durations during day (a) and
night (b). Data are composed of concatenated 30-min samples, selected at
random, one from each dolphin, "n" refers to the number of individual
surfadngs, and is not a reference to any averaged 30-min sample.

55

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57

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>V> 52

19

8 9 10 11 12 13 14 15 16 17 18 19
Hour of Day

Figure 12. Mean group sizes by survey (a) and hour (b), error bars indicate 1
SD. Group sizes from 1200-1259 were significantly higher than those at all
other times except 13 hr, group sizes from 1300-1359 were significantly
higher than those at 9-11, 14, 16, and 19 hr (Fishers LSD).

58

P < 0.0001 , Kmskal-Wallis

I

c

«

N

Oi

a

I

Behavior

Figure 13. Mean group sizes by behavior, error bars indicate 1 SD.
Socializing occurred in sigiuficantly larger groups than other behaviors
(P < 0.005, Fisher's LSD).

59

n = 265 observations

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>

ra
1

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08
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T-»'

^J^

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n

40

80 120 160 200 240 280
Travel Direction (degrees
magnetic)

320 360

Figure 14. Histogram of observed travel directions.

60

1 13 km'^ photo survey "recaphore" area y-.-'-.V

Gulf of Mexico

Figure 15. Assumed minimum area occupied by estimated dolphin
population.

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67

Table 4. Mean half-weight index of association values for non-calf freeze-
branded dolphins seen at least five times.

Dolphin

In assoc.
with

Mean

SD

n

Min.

Max.

Median

FB502

Males

0.141

0.070

2

0.091

0.190

0.141

FB503

Males

0.131

0.045

3

0.100

0.182

0.111

FB504

Males

0.102

0.048

6

0.059

0.190

0.091

FB505

Males

N/A

N/A

0

N/A

N/A

N/A

FB507

Males

0.153

0.082

2

0.095

0.211

0.153

FBSll

Males

0.107

0.036

4

0.069

0.143

0.108

FB512

Males

0.144

0.054

2

0.105

0.182

0.144

FB514

Males

0.077

N/A

1

0.077

0.077

0.077

FB515

Males

0.084

0.033

3

0.057

0.121

0.074

FB516

Males

0.080

N/A

1

0.080

0.080

0.080

FB518

Males

0.083

0.020

5

0.059

0.114

0.080

FB521

Males

0.104

0.030

5

0.074

0.146

0.111

FB522

Males

0.106

0.022

7

0.069

0.125

0.114

FB538

Males

0.161

0.073

5

0.077

0.250

0.182

FB502

Females

N/A

N/A

0

N/A

N/A

N/A

FB503

Females

0.111

0.052

2

0.074

0.148

0.111

FB504

Females

0.092

0.024

4

0.057

0.114

0.098

FB505

Females

0.087

0.034

2

0.063

0.111

0.087

FB507

Females

0.127

0.023

2

0.111

0.143

0.127

FBSn

Females

0.067

N/A

1

0.067

0.067

0.067

FB512

Females

0.134

0.053

3

0.077

0.182

0.143

FB514

Females

0.148

0.055

3

0.111

0.211

0.121

FB515

Females

0.118

0.048

3

0.063

0.148

0.143

FB516

Females

0.286

N/A

1

0.286

0.286

0.286

FB518

Females

0.108

0.054

2

0.069

0.146

0.108

FB521

Females

0.071

0.005

2

0.067

0.074

0.071

FB522

Females

0.125

0.059

2

0.083

0.167

0.125

FB538

Females

0.094

0.034

3

0.074

0.133

0.074

68

Table 4, continued.

Dolphin

In assoc.
with

Mean

SD

n

Min.

Max.

Median

FB502

All

0.141

0.070

2

0.091

0.190

0.141

FB503

All

0.123

0.042

5

0.074

0.182

0.111

FB504

All

0.098

0.044

8

0.057

0.190

0.091

FB505

All

0.087

0.034

2

0.063

0.111

0.087

FB507

All

0.140

0.051

4

0.095

0.211

0.127

FB511

All

0.099

0.036

5

0.067

0.143

0.083

FB512

All

0.138

0.047

5

0.077

0.182

0.143

FB514

All

0.130

0.057

4

0.077

0.211

0.116

FB515

All

0.101

0.041

6

0.057

0.148

0.098

FB516

All

0.183

0.146

2

0.080

0.286

0.183

FB518

All

0.090

0.030

7

0.059

0.146

0.080

FB521

All

0.095

0.029

7

0.067

0.146

0.077

FB522

All

0.103

0.022

8

0.069

0.125

0.105

FB538

All

0.136

0.068

8

0.074

0.250

0.114

69

Table 5. Mean half-weight index of association values for same-sex and
opposite-sex associations among freeze-branded dolphins. Values are derived
from means of individuals shown in Table 4.

Pair

Mean

SD

Min.

Max.

n

Male-Male

0.110

0.032

0.080

0.160

8

Female-Female

0.098

0.026

0.070

0.130

6

Opposite-sex

0.129

0.056

0.080

0.290

12

Overall

0.119

0.027

0.090

0.180

14

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(14

u.

72

Table 7. Observed frequencies of behaviors in each habitat type.
Behavior Channel Bay Jetty Offshore Total

FBS

1

22

0

1

24

3.9%

Feed

104

50

19

0

173

28.4%

Socialize

20

32

3

2

57

9.4%

Travel

172

119

18

0

309

50.7%

Mill

6

15

3

0

24

3.9%

Unknown

10

10

2

0

22

3.6%

Total

313

248

45

609 100%

73

Table 8. Mean direction of travel for eight surveys.

Survey Mean direction 95%CI

(degrees magnetic)

May 1992

45

>90

14

July-August 1992

1

25

151

September 1992

342

>90

10

October 1992

8

50

12

December 1992

310

42

23

January 1993

10

45

24

March 1993

8

53

21

June 1993

283

62

10

74

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76

APPENDIX 1

SUMMARY INFORMATION FOR ALL DOLPHINS CAPTURED
(portions after Sweeney 1992)

Name

Sex Age* (yr) Comments

FB501 (RT3) F 17

FB502 (RTl) M 16

FB503 F 21

FB504 (RT2) M 18

FB505 (RT4) F

FB506

FB507

FB508

M

8

M 11

16

Tagged 10 July 1992. Initially
identified in May 1992 survey.

Tagged 9 July 1992. Initially identified
in May 1992 survey.

Tagged 10 July 1992. Pregnant (1st
trimester), lactating. Mother of
FB508.

Tagged 9 July 1992. Iititially identified
in May 1992 survey.

Tagged 11 July 1992. Pregnant (1st
trimester).

Tagged 9 July 199Z

Tagged 11 July 1992. Mother of FB509.
Pregnant (1st trimester). Initially
identified in May 1992 survey.

Tagged 10 July 1992. Calf of FB503. FB
looks Uke "500".

* From inspection of dental growth layer groups unless otherwise noted. Age data provided
by NMF5. Matagorda Bay dolphins nvay be smaller than other Gulf coast dolphins. Based
on length, age of these dolphins was underestimated. There was a discrepancy of 45 ± 7.40
(SD) years (younger) between length based estinutes and the nr»ore accurate GLG estimates.

77

Appendix 1, continued.

Name

Sex Age (yrs) Comments

FB509

FB510

M

2b

FB511 (RT5)

F

19

FB512

M

7

FB513

F

lb

FB514 (RIV)

M

19

FB515 (RT6)

F

12

FB516

M

10

FB517

F

2b

FB518 (RT8) M

11

Tagged 11 July 1992. Calf of FB507.
Initially identified in May 1992
survey.

Tagged 11 July 1992.

Tagged 12 July 1992. Mother of FB513.
Pregnant (1st trimester), lactating.

Tagged 11 July 1992.

Tagged 12 July 1992. Calf of FB511

Tagged 14 July 199Z

Tagged 14 July 1992. Mother of FB517.
Lactating.

Tagged 14 Jxxly 1992.

Tagged 14 July 1992. Calf of FB515.
"51" of left side of fin unreadable.
Dead: TMMSN ID# P0249.
Collected 13 September 1992. Last
seen 6 Sepembo" 1992. Died of
intestinal infarction (necrosis due to
twisted intestine) unrelated to
capture.

Tagged 15 July 1992.

No tooth collected. Age estimate based on length, from Sweeney (1992).

78

Appendix 1, continued.

Name

Sex Age (yrs) Comments

FB519

FB527

31

Tagged 14 July 1992. Possibly pregnant
(early).

FB520

M

2b

Tagged 15 July 1992. Calf of FB521.

FB521 (RT9)

F

31

Tagged 15 July 1992. Weak cross bar
on "2", left side of fin. Mother of FB
520. Pregnant (1st trimester),
lactating.

FB522 (RTIO)

M

8

FB523

F

34

FB524

M

11

FB525

F

S-ib

FB526

M

10

22

Tagged 15 July 1992. Initially
identified in May, 1992 survey.

Tagged 17 July 1992.

Tagged 17 July 1992.

Tagged 17 July 1992.

Tagged 17 July 199Z Middle bar of "6"
pocHT CH\ left side fin.

Tagged 17 July 1992. Pregnant (1st
trimester), lactating.

FB528

M

3-5"

Tagged 17 July 1992.

FB529

F

6

Tagged 18 July 1992.

FB530

M

22

Tagged 18 July 1992

FB531

F

3-tb

Tagged 18 July 1992.

79

ApjDendix 1, continued.

Name

Sex Age (yrs) Comn\ents

FB532

FB534

FB536

FB538

M

M

M

M

Rototag 412 M

21

10

11

2b

Tagged 18 July 1992.

Tagged 19 July 1992.

Tagged 19 July 1992. Brand looks like
"535"

Tagged 19 July 1992. Initially
identified in May, 1992 survey.

Tagged 10 July 1992. Not freeze-
branded.

80

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83

Bh

Port O'Connor, TX area
f 4krT>

FB503 Without calf, June 1993

Appendix 3a. Sightings of FB503 and calf, FB508, during the nine photo-
identification surveys. "C" denotes the capture location.

85

B509 without mother, June 1 993

App)endix 3b. Sightings of FB507 and calf, FB509, during the nine photo-
identification surveys. "C" denotes the capture location.

86

Port O'Connor,

Appendix 3c. Sightings of FB512 during the nine photo-identification
surveys. "C" denotes the capture location.

87

•FB516
nFB519

;:^^::.e^:i^^-i-;:-.-::-~s:-^^^^

88

Port O'Connor, TX area

■ V-?/vV-.;A-«vV---'" ■ ■ ■

•FB534
aFB536
ofB538

, I,-'. •% •\

Appendix 3e. Sightings of FB534, FB536, and FB538 (captured together),
during the nine photo-identification surveys. "C" denotes the capture
location.

89

Port OConnor, TX area

FB530, FB532

FB52

%

4kfn

^FB506

Appendix 3f. Capture locations of freeze-branded dolphins not seen during
the nine photo-identification surveys.

90

Port O'Connor, TX jirea
JN —

OlOJul
•11-16 Jul
D17-27JUI

° ° ^ *

Appendix 4a. FB501 radio-telemetered and sighted positions during
tracking period. From 27 July-6 September FB501 was out of range
(presumably in San Antonio Bay, positions not shown).

91

Port O'Connor, TX area

4 4 km
P'

•9-18 Jul
D19-28JU1

Port O'Connor, TX area
In ^^"^

029 Jul-7Aug
+ 8- I 6 Aug

Appendix 4b. FB502 radio-telemetered and sighted positions during
tracking period.

92

Port O'Connor, TX area
^^ 4 km

• 9- 14 Jul
a 15- 18 Jul

Appendix 4c. FB504 radio- telemetered and sighted positions during
tracking period.

93

Port O'Connor, TX area

•H-MJol
°'5-18JuJ
♦» 9- 23 Jul

App)endix 4d. FB505 radio-telemetered and sighted positions during
tracking period.

94

+ +

+

Port OX:onnor, TX area
♦ 4km

• 12- 17 Jul
ai8-22Jul
♦23-27 Jul
+28 Jul- 1 Aug

Appendix 4e. FB511 radio-telemetered and sighted positions during
tracking period.

95

Port O'Connor, TX cirea
^ 4 km

• 1 4- 1 8 Jul
a 19-23 Jul

♦ 24-28 Jul

+ 29 Jul- 1 Aug

App)endix 4f. FB514 radio-telemetered and sighted positions during
tracking period.

96

Port O'Connor, TX area
♦ 4 km

• 1 4- I 9 Jul
O20-24JuI

♦ 25-29 Jul
•l-30Ju1-3Aug

Appendix 4g. FB515 radio-telemetered and sighted posiHons during
tracking period.

97

Port O'Connor, TX area
km

• 15-29 Jul

□ 26 Ju1-4Au4

♦ 5-14Aug

Port O'Connor, TX area

^ 4km
fit

♦ 15-24 Aug
+25-31 Aug

1 -3 Sep no contact
X 4- 13 Sep

Appendix 4h. FB518 radio-telemetered and sighted positions during
tracking period.

98

Port O'Connor, TX area
^^ 4 km

• 15-21 Jul
D 22- 27 Jul

Port O'Connor, TX area
4^ 4km

«28Jul-2Au9
+3-10Aug

Appendix 4i. FB521 radio-telemetered and sighted positions during
tracking f>eriod.

99

Port O'Connor, TX area

•17-23 Jul
024-29JUI

Port O'Connor, TX area

|n>

o30 Jul-4Aug
+ 5-1 1 Aug

Appendix 4j, FB522 radio-telemetered and sighted positions during
tracking period.

100

■■■/••■> L

\V \'- \.^0^\T\ /•': '•'.' "■'-• ■•'.- ^V ^?^?*>'.* ^V ••*

Port O'Connor, TX area ■•■••V/-/^^^ ■■'&\v.^?5^ ^

• 23:00-01
005:00-08:

♦ 11:00-13:
+ 18:00-20:

00 n«0
00 n«2
00n=5
00 n=2

• 23:00-01:00 n-7
005:00-08:00 n«14

♦ 1 1:00-13:00 n»16
+ 18:00-20:00 n»18

Appendix 5a. Positions of FB501 (1) and FB502 (2) by time of day over the
radio-tracking period, from radio-telemetry and sightings.

101

Port OConnor, TX area
^^ 4km

• 23:00-01 00 n=5
0 05:00-08:00 n=9
*11:00-13:00n=17
+ 18:00-20:00 n=10

Port O'Connor, TX area

• 23:00-

•01

00n«2

□ 05:00-

08

00 n«4

♦ 11:00-

13

00n=7

+ 18:00-

20

00n=5

Appendix 5b. Positions of FB504 (1) and FB505 (2) by time of day over the
radio-tracking period, from radio-telemetry and sightings.

102

• 23:00-01.00 n-6
005:00-08:00 n»1

♦ 11:00-13K)0 n»10
+ 18:00-20:00 n*4

• 23:00-01:00 n«4
0 05:00-08:00 n>3

♦ I 1:00-13:00 n-6
+ 18:00- 20:00 n-5

Appendix 5c Positions of FB514 (1) and FB515 (2) (captured together) by
time of day over the radio- tracking p)eriod, from radio-telemetry and
sightings.

103

• 23:00-01:00 n»5
□ 05:00-08:00 n»4

♦ 1 1:00-13:00 n=7
+ 18:00-20:00 n=9

• 23:00-01:00 0=6
005:00-08:00 n=4
^1 1:00-13:00 n=12
+ 18:00-20:00 n»8

Appendix 5d. Positions of FBSll (1) and FB522 (2) by rime of day over the
radio-tracking period, from radio-telemetry and sightings.

104

Port O'Connor,

• 23:00-01.00 n=5
□ 05:00-08:00 n=5

♦ 1 1:00-13:00n=11
+ 18:00-20:00 n=7

Appendix 5e. Positions of FB521 (captured with FB518) by time of day over
the radio-tracking period, from radio-telemetry and sightings.

105

106

APPENDIX 6

SUMMARY OF OBSERVATIONS ON BIOPSY WOUNDS

Dolphin

Date

Days

Observations

elapsed

(length by height, mm)

1. FB502 (RTl)

9 Jul 92

0

Captured and biopsied. VHE> = B.

19 Dec 92

163

Small darkly pigmented sfX)t. By
contrast, radio bolt holes are
darker.

2. FB503

10 Jul 92 0

20 Mar 93 253
14 Jul 93 369

3. FB505(RT4) 11 Jul 92 0

21 Mar 93 253

Captured and biopsied. Pregnant
(1st trimester), lactating mother.
VHE = B.

Not noticeable.

Not noticeable

Captured and biopsied. Pregnant (1st

trimester). VHE = A.
Small, lighter spot (21.4 x 14.2). By

contrast, radio bolt holes are

darker.

4. FB507

5. FB509

11 Jul 92 0

20 Dec 92 162

20 Mar 93 252

11 Jul 92 0

Captured and biopsied. Pregnant (1st
trimester). Mother of FB509. VHE
= A.

Not noticeat4e (poor photo).

Small darker spot (15.1 x 5.0)

Captured and biopsied. Calf of
FB507. VHE = B. Fresh wound
appears oval and pink, several
nun deep. No other discoloration.

' Veterinarian Health Evaluation: A = "no health concerns", B = "would Ijenefit from repeat
evaluation", C = "would benefit from therapeutic intervention", D = "serious health
concerns" (Sweeney 1992).

107

Appendix 6, continued.

Dolphin

Date Days Observations

elapsed (length by height, mm)

20 Mar 93 252
6. FB511 (RT5) 12 Jul 92 0

23 Jul 92 11

21 Dec 92 162

7. FB514 (RT7) 14 Jul 92 0
24 Oct 92 102

20 Dec 92 159

16 Jun 93 337

8. FB515 (RT6) 14 Jul 92 0

6 Aug 92 23

12 Jan 93 112

Not noticeable.

Captured and biopsied. Pregnant (1st

trimester), lactating mother. VHE

= A.
VS^te to pinkish oval (20.5 x 9.8)

with band of darker than normal

skin (3.3 mm wide) at edges of

wound.
Normally pigmented scar tissue (?)

or not noticeable.

Captured and biopsied. VHE = B.
No sign of biopsy. By contrast, radio

bolt holes appear as small dark

spots surrounded by lighter halo

where stainless steel

washers /magnesium nuts were.
As above.
As above.

Captured and biopsied. Mother of
FB517. Lactating. VHE = A.

Pale gray halo (3.9 mm wide)
surrounding white oval (16.2 x
13.2) with darker spot in center
(3.6 mm diameter). No other
discoloration.

Appears to be spot of pigmented scar
tissue. By contrast, radio bolt

108

Appendix 6, continued.

Dolphin

Date Days Observations

elapsed (length by height, mm)

holes are very d«irk spots with
whiter halo fading into normal
skin.

9. FB516

14 Jul 92

0

12 Jan 93

182

10. FB517

14 Jul 92

0

13 Sep 92 61

11. FB518 (RT8) 15 Jul 92 0
26 Aug 92 42

12. FB520

15 Jul 92 0

13. FB521 (RT9) 15 Jul 92 0

23 Jul 92 8

Captured and biopsied. VHE = A.

No sign of biopsy.

Captured and biopsied. Calf of
FB515. VHE = C.

Collected freshly dead (TMMSN ID#
P0249). Died of intestinal
infarction unrelated to capture
(TMMSN 1992). Shallow,
diamond shap)ed indentation,
measuring 21x12 mm, normal
pigmentation (TMMSN 1992)

Captured and biopsied. VHE = A.
Small white spot (17.5 x 9.4).

Captured and biopsied. Calf of
FB521. VHE = A. Fresh wound
appears as deeply pink, oval (29.6 x
15.8) , several mm deep. No other
discoloration.

Captured and biopsied. Mother of
FB520. Pregnant (1st trimester),
lactating. VHE = B.

Oval wound (22.5 x 12.2), white to
pinkish with darker spot (4.0 mm
diameter) in center. Skin at edge

109

Appendix 6, continued.
Dolphin Date

Days Observations
elapsed (length by height, mm)

30 Jul 92

15

24 Aug 92

40

24 Oct 92

101

. FB522 (RTIO) 17 Jul 92

0

4 Aug 92

18

15. FB534

19 Jul 92
1 Aug 92

0
13

. FB536

19 Jul 92

0

14 Aug 92

26

7 Jul 93

353

. FB538

19 Jul 92

0

(2.7 mm wide band) darker on

ventral portion.
White spot (poor photo).
White spot fading into normal skin.

No other discoloration, no

apparent indentation.
Lighter gray spot (29.0 x 13.3).

Shallow indentation?

Captured and biopsied. VHE = A.

Diamond shaped white to pinkish
wound (37.2 x 22.1). Darker
pinkish horizontal band (12.1 x
5.6) in center. Along dorsal edge,
skin at edge of wound (3.2 mm
band width) is slightly darker than
normal nearby skin otherwise a
lighter gray halo fading into
normal skin.

Captured and biopsied. VHE = B.
Oval wound with white edges,

darker (pinkish) at center (poor

photo).

Captured and biop)sied. VHE = A.
White oval (32.7 x 18.6).
Darkly pigmented oval spot (14.4 x
8.5).

Captiired and biopsied. VHE = A.

110

Appendix 6, continued.

Dolphin Date Days Observations

elapsed (length by height, mm)

13 Jul 93 359 Normally pigmented spot (31.1 x

13.5) with lighter oval outiine. By

contrast, rototag hole has left a

small, very dark spot v^ith paler

halo fading into normal skin.

7 Nov 93 476 As above (10.5 x 6.2). Diamond

shaped outline of paler skin.

Comments re rototag as above.

Ill