Thesis (M.S.)--Naval Postgraduate School, 2002. / Thesis advisor(s): Thomas G. Muir, Steven R. Baker, Samuel H. Ridgway. Includes bibliographical references (p. 129-130). Also available online.

During long-term studies of dolphins, the number of individuals in the population being studied are constantly monitored using the technique of photo-identification. This constant monitoring makes use of different researchers over time. Therefore, measurement of photographic quality and individual distinctiveness for photo-identification analyses was incorporated in this dissertation to provide an additional data set for analysis. Researchers with differing levels of experiences did not obtain the same information from the same photograph and were unable to reliably quantify variables of photo quality and individual distinctiveness, but experienced researchers were found to be more adept than inexperienced researchers in counting notches on the dorsal fin of bottlenose dolphins. These results highlight the necessity for researchers to be trained in photo-identification techniques prior to carrying out their study. This study theodolite tracked dolphins off Durban from June 2004 to Feb 2005 to assess habitat utilization of bottlenose dolphins (Tursiops aduncus) in the Durban bay region. Dolphins were seen in all months surveyed and throughout the survey area. Temporal distribution of dolphins was skewed with 91% of dolphins seen before midday and 98% of sightings observed in water depths less than 30m. Six behavioural categories were recorded, including: social, fast travel, slow travel, feeding, resting and milling. The most dominant behaviour exhibited by dolphins was slow travel (46%) followed by feeding (27%). Resting was not observed at all. Of the feeding behaviour 88% occurred in the southern end of the bay whereas other behaviours occurred randomly throughout the survey area. Additional theodolite tracks were conducted during experimental boat approaches (before, during and after boat approaches) to determine potential short-term reactions of dolphins to dolphin watching boats. Two speeds of approach (slow ~ < 5 km/hr and fast ~ > 40 km/hr) and two distances of approach (20m and 80 m) were tested. The bottlenose dolphin groups did not change their behaviour in response to boat approaches during any of the periods of experimentation. Short-term changes in group speed, group size and spread were not statistically significant. Dolphin groups continued with their ‘normal’ behaviour and spent the same amount of time in the bay when compared to their distribution and behaviour in the absence of the experimental boat. These findings indicate that the experimental boat did not affect the behaviour of dolphins at either a slow or fast approach and even at a close distance. This is interpreted as being as a result of habituation of the dolphins due to their residency in a busy port. This work is crucial in developing guidelines for the development of a sustainable dolphin watching industry off Durban. / Thesis (M.Sc.) - University of KwaZulu-Natal, Durban, 2008.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1976. / Bibliography: leaves 113-121. / Microfiche. / vii, 121 leaves ill. 29 cm

Common bottlenose dolphins (Tursiops truncatus) are apex predators and indicators of localized ecosystem health. Accurate characterization of population demography is crucial to parameter predictions. However, descriptions of age growth investigations of odontocetes are limited to the postnatal life. In contrast, the modeled scenario for terrestrial mammalian growth has been described along a continuum of pre- and postnatal data. Few age distribution data exist for the western Gulf of Mexico despite the fact that life tables enable demographic comparisons among populations. The objective of this study was to characterize age, growth, and population-level behavior of bottlenose dolphins along Texas. This objective was accomplished by two discrete studies: age analysis, and population-level behavior. Teeth from 290 stranded individuals were extracted for the purposes of age determination. Curvilinear models (the Gompertz and the von Bertalanffy) were fit to postnatal length-at-age data. Fetal age was determined for 408 suspected fetal length records using validated fetal growth trends and empirical measurements from late-term fetuses. Growth analysis indicated that a Gompertz model fit length-at-age data better than a von Bertalanffy model. A postnatal Gompertz model explained less variation than a combined pre- and postnatal model (R2 = 0.9 and 0.94 respectively). The absolute growth rate and rate of growth decay tripled with the inclusion of fetal length and age data. In the second study, life tables were constructed for 280 individuals. Survivorship curves, mortality rates, intrinsic capacity for increase, and the population growth rate were calculated. Bottlenose dolphin mortality did not differ significantly by sex or age class. Survivorship was best characterized by a type III curve. Analyses indicated no substantial increase (r = -0.07), and that the population is not replacing itself in the next time-step (y = 0.93). Bottlenose dolphins conform to a number of eutherian mammalian trends: the production of precocial young, calving seasonality, and rapid fetal growth rate. Population level behavior suggests a population retraction possibly as a compensatory response to ecosystem perturbation rather than a population decline. Reproductive information will confirm population status and stability in the future. This study is the first to demonstrate a significant impact of cetacean fetal growth parameters on postnatal growth trajectory.

Thesis (M.S.)--University of North Carolina at Wilmington, 2002. / Includes bibliographical references (leaves : [49]-50).

The Indo-Pacific bottlenose dolphin (Tursiops aduncus) is a common top predator along the KwaZulu-Natal coast. There have been several dietary studies done on this species, most of which have classed this predator as an opportunistic feeder preying on the most abundant prey species in that area. In KwaZulu-Natal (KZN) a dietary study was carried out in 1990, but there have been no followup studies to examine potential changes in diet. A number of bottlenose dolphins get entangled in the shark-nets set off the KZN coast each year. These dolphins provide a valuable source of information about different aspects of the ecology of this population. The aim of this study was to examine the diet of bottlenose dolphins off the KwaZulu-Natal coast with particular emphasis on temporal change in diet composition. The contents of 102 stomachs of bottlenose dolphins (58 females, 44 males) accidentally caught in the shark nets between 1985 and 2010 were analysed, and compared to historical data from dolphins caught between 1975 and 1986. A total of 94 different prey species from 37 families (32 fish families, five cephalopod families) were identified in the stomach contents. Teleosts made up the most important prey group in numbers and weight constituting 84 percent and 67 percent, respectively, while cephalopods made up 15 percent of the number and 30 percent of the weight of the prey items. Multi Dimensional Scaling (MDS) indicated that there is no resource partitioning between males and females, but significant partitioning between juveniles and adults. Six prey species contributed more than 60 percent of the weight of all prey species in the diet. These species are the most important according to their calculated index of relative importance score and are, in order of importance: Sepia sp. (cuttlefish)., Pomadasys olivaceus (piggy), Trachurus delagoa (maasbanker), Scomber japonicus (mackeral), Loligo sp. (squid). and Pagellus bellottii natalensis (pandora or red tjor-tjor). When compared to historic data, no changes in the main prey species has occurred, but the piggy has decreased in importance (1976-1986 percent IRI=45; 2000-2010 percent IRI=22), while the maasbanker has increased (1975-1986, percent RI=4; 2000-2010 percent RI=20). Stable carbon and nitrogen isotope analysis performed on tissue from the teeth of T. aduncus caught in the shark nets between 1970 and 2010 showed that there has been no significant shift in trophic level (δ15N) or in primary prey source (δ13C) over this time. The isotopic signatures of different tissues from an individual were used to create a base line and describe the differences in tissue signatures. Blubber was found to be significantly different from skin and muscle, which were found to be isotopically similar. Skin from remote biopsies can therefore probably be used in place of muscle for isotopic studies of bottlenose dolphins, while caution should be taken when using blubber. Given that T. aduncus is still listed as “data deficient” by the International Union for the Conservation of Nature (IUCN), and the potential for climate change and expanding fisheries to alter the distribution and abundance of their prey species, long term dietary studies such as this are important in order for their effective conservation and management.

In an attempt to correlate genetic data with possible species delineation, this study investigates the presence of chromosomal variants between the North Atlantic bottle nose dolphin, Tursiops truncatus, and the North Pacific bottle nose dolphin, T. gilli. Blood samples were obtained from oceanaria in the United States. Location of capture was correlated with karyotype to compare chromosome morphology with geographic range.

The Eastern Scottish population of bottlenose dolphins (Tursiops truncatus) is the northernmost population of this species. The resident core of this population consists of 120 to 150 different individuals. This small size and its geographical isolation from other populations raises questions about its viability and whether the population has behavioural patterns that differ from those common to other populations of the same species. Microsatellite genetic diversity was low and mitochondrial DNA genetic diversity values were lowest in East Scotland compared to other populations worldwide and to neighbouring populations around UK waters. It has been well documented, from four different field sites worldwide, that male bottlenose dolphins form alliances with preferred male associates. These alliances can last for several years and the males involved show association coefficients similar to those of mothers and calves (0.8-1.0). These alliances appear to be of great importance in obtaining matings for the males. In the Eastern Scottish population males do not form alliances. No evidence of strong associations between individuals of either sex was found and there was no correlation between association and relatedness patterns. I suggest that the isolation and small size of the population together with reduced genetic diversity affects the pressure of kin selection for altruistic behaviours. There is no gain in competing or associating with close relatives for access to mates and it might be more important to avoid inbreeding by dispersing. Although evidence of gene flow between East Scotland and its neighbouring populations was not confirmed with Bayesian clustering analysis, a small set of individuals from Wales were found to be closely related to individuals from the East Coast of Scotland. In general the dynamics found in UK water populations resemble those of the Western North Atlantic with sympatric populations of coastal as well as pelagic individuals.

The population of bottlenose dolphins off the east coast of Scotland has been studied since the late 1980s, initially focused on the inner Moray Firth, where a Special Area of Conservation (SAC) was designated under the EU Habitats Directive. The population has since expanded its distributional range and currently ranges from the Moray Firth to the Firth of Forth. The main aims of this thesis were: (1) to estimate population parameters for this population using a 25 year individual recognition dataset, and (2) to increase knowledge of the distribution and abundance of dolphins in areas outside the SAC, especially to investigate areas of high use in St Andrews Bay. Apparent survival rate for adults and sub–adult dolphins was estimated at 0.946 (SE=0.005) accounting for temporary emigration caused by the population's range expansion. Sex-specific survival was estimated for males (0.951, SE=0.013) and females (0.956, SE=0.011) using multistate models to minimize bias caused by individuals of unknown sex. Using a newly developed approach, fecundity rate was estimated at 0.222 (95% CI=0.218-0.253) from an expected mean inter-birth interval of 4.49 yrs (95% CI=3.94-4.93). Total population size was estimated as ~200 individuals, after accounting for temporary emigration and for heterogeneity in capture probabilities. In St Andrews Bay, an area used regularly in summer by approximately half the estimated population, habitat use modelling identified the entrance to the Firth of Tay and waters around Montrose as high use areas for dolphins, whose presence was influenced by tidal current speed and direction. The results suggest that the conservation and management plan for this small and isolated population of bottlenose dolphins should be reviewed to adapt it to current knowledge, especially regarding the uncertainty around the potential impacts of offshore renewable energy developments off the east coast of Scotland.

Geographic variation in the whistle vocalisations of dolphins has previously been reported. However, most studies have focused on the whole whistle repertoire, with little attempt to classify sounds into biologically relevant categories. Common bottlenose dolphins (Tursiops truncatus) use individually distinctive signature whistles which are thought to help maintain contact between conspecifics at sea. These whistles may show a different kind of variation between populations than non-signature whistles. Here I investigate signature whistle use and variation in the two recognised species of bottlenose dolphins (T. truncatus and T. aduncus) from populations inhabiting the coastal waters of the North America, Scotland, South Africa, Tanzania, Japan, Australia and New Zealand, and one captive colony. I identified likely signature whistles (signature whistles types, SWTs) from acoustic recordings by combining two novel techniques: automated contour categorisation in ARTwarp (Deecke and Janik, 2006) and a specific bout analysis based on the timing of signature whistle production in T. truncatus termed SIGID (Janik et al. in press). Three ways of categorising the contours were tested and between 87 and 111 SWTs were identified in total. Repeated emissions of stereotyped contours were apparent in the repertoire of all T. aduncus populations using both automated and human observer categorisation, providing good evidence for signature whistle use in this species. There was significant inter-specific variation in the frequency parameters, looping patterns and duration of SWTs. Inflection points, duration and measures of SWT complexity showed high variation within populations, suggesting inter- and intra-individual modification of these parameters, perhaps to enhance identity encoding or convey motivational information. Using 328 bases of the mtDNA control region, I found high levels of population differentiation (FST and φST) within the genus Tursiops. These data do not support a link between mtDNA population differentiation and variability in call type. Instead, morphological variations at the species level, and learned differences at the population level, better explain the variation found.