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.

Bottlenose dolphins of the Kvarnerić (NE Adriatic Sea) live in an area of increasing human impact, through tourism and small-scale fisheries. This thesis aimed to assess the status of the local population and to inform managers on factors affecting their distribution and abundance, using data from 1995-2003. Habitat modelling indicated a significant negative impact of proximity to the main ‘marine highway’ and to marine petrol stations. Evidence was found that dolphins may recently have reached a tolerance limit to the number of boats using the area and that they remember crowded areas from one year to the next. Dolphin presence was positively related to particular depths and trawling areas. Apparent adult survival rate was estimated to be significantly lower than for any other bottlenose dolphin population and first year calf survival was also low. A decreasing trend in fecundity rate was found. The population showed a considerable rate of non-random temporary emigration from the study area. The estimated size of the population was small and similar to two other European bottlenose dolphin populations (Moray Firth in Scotland and Shannon Estuary in Ireland). A significant decrease in abundance of about 39% from 1995 was estimated. PVA confirmed the importance of female adult survival to population viability and indicated that the current rate of human-induced mortality is unsustainable. Local extinction risk within three generations was estimated to be high (35%). Applying the IUCN Red List Criteria, the Kvarnerić population should be listed as Endangered under Criterion C and E. This study gives an important insight into the ecology of Adriatic bottlenose dolphins and indicates the need for a regionally and locally synergistic approach to conserve this population.

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.

The ranging behaviour, habitat preferences, genetic structure, and demographic parameters of bottlenose dolphins living in the Azores were studied using data collected from 1999 to 2004. Only 44 dolphins out of 966 identified were frequently sighted within and between years and showed strong site fidelity. The remaining individuals were either temporary migrants from within or outside the archipelago, or transients. Estimates of home range size were three times larger than previously reported for this species, possibly as a result of the lower availability of food resources. Mitochondrial DNA sequences showed very high gene and nucleotide diversity. There was no evidence of population structuring within the Azores. The Azorean population was not differentiated from the pelagic population of the Northwest Atlantic, suggesting the "unproductive" waters of the Atlantic do not constitute a barrier to dispersal. Population size, survival and temporary emigration rates were estimated using open-population models and Pollock's robust design. A few hundreds of dolphins occur in the area on a given year, though the majority should use it temporarily, as suggested by the high emigration rates. Bottlenose dolphins preferentially used shallow areas with high bottom relief. Temporal and spatial persistence of dolphin-habitat associations documented in this study further supports the idea of a close relationship between certain bathymetric features and important hydrographic processes and suggests the occurrence of prey aggregations over these areas may be, to some extent, predictable. Several results of this study suggest there are no reasons for concern about the status of this population. Yet, the resident group may be negatively affected by increasing pressure from the whale watching activity. Although the proposed Marine Park constitutes important habitat for resident dolphins, at present, the area is clearly insufficient to satisfy their spatial requirements and its conservation value may be limited.

The bottlenose dolphins of Fiordland, New Zealand, live at the southern limit of the species' worldwide range. They are exposed to impacts from tourism and habitat modification, particularly in Doubtful Sound, and their conservation requirements are presently unclear. Dolphin abundance was estimated in Doubtful Sound using photo-identification census and capture-recapture techniques (56 individuals; 95% CI: 55-57), detecting a decline of 34-39% over 12 years among adults and sub-adults (>3 years old). The cause of this decline was investigated via demographic modelling in Doubtful Sound and a comparative assessment of population status in Dusky Sound. Capture-recapture modelling of photo-identification data compiled since 1990 yielded a constant adult survival rate marginally lower than prior estimates for wild bottlenose dolphins ([phi]a(1990-2008) = 0.9374; 95% CI: 0.9170-0.9530). Survival of calves (<1 year old) declined to an unsustainable level that is thought to be the lowest recorded for wild bottlenose dolphins ([phi]c(2002-2008) = 0.3750; 95% CI: 0.2080-0.5782) coincident with the opening of a second tailrace tunnel for a hydroelectric power station. Reverse-time capture-recapture modelling detected declines in recruitment (f(1994-2008) = 0.0249; 95% CI: 0.0174-0.0324) and population growth ([lambda](1994-2008) = 0.9650; 95% CI: 0.9554-0.9746) over time consistent with the decline in calf survival (<1 year old) and a separate reduction in juvenile survival (1 to 3 years old) reflecting cumulative impacts. Dolphin abundance was estimated in Dusky Sound using photo-identification census and capture-recapture techniques (102 individuals, 95% CI: 100-104) providing no evidence of interchange with Doubtful Sound. A comparative assessment of health status between Doubtful and Dusky Sounds revealed skin lesioning was more severe in Doubtful Sound, particularly among females, and newborn calves appeared to be smaller and were born over a shorter period: factors that may contribute to the low levels of calf survival in Doubtful Sound. The Fiordland bottlenose dolphins were assessed under IUCN Red List regional criteria. The small size of the population (205 individuals, 95% CI: 192-219) combined with the projected rate of decline in stochastic matrix models (average decline 31.4% over one generation) resulted in a recommended classification of Critically Endangered.

Coastal dolphins are often exposed to habitat degradation and direct interactions with humans. Major factors that influence dolphin distribution, critical for conservation concerns, are still poorly understood even for the bottlenose dolphin, the best-studied cetacean. To establish the environmental conditions that best predict occurrence of bottlenose dolphins and high feeding densities in Galveston Bay, I conducted a total of 367 boat surveys in five locations of the estuary, totaling 3,814.77 km of search effort. I counted groups of dolphins and measured surface water temperature, salinity, turbidity, total number of boats, shrimp vessels, and number of seabirds. Using geospatial tools, these data -- along with location, distance to the Gulf of Mexico and water depth -- were analyzed on a 500- m resolution grid. Temporal factors at daily and seasonal scales were also examined. Occurrence was modeled using a Generalized Additive Model and core feeding densities (i.e., feeding densities above 2 SD of the mean) were modeled with a Generalized Linear Model. A total of 1,802 dolphins in 262 groups were detected, 56.87% of which were feeding. I found that all factors except warm/cold seasons and turbidity were useful to predict dolphin distribution, which was related non-linearly to most predictors. Fewer variables were relevant in predicting core feeding densities. These were, in decreasing order of relevance, distance to the Gulf of Mexico, surface water temperature, depth, number of boats, and warm/cold seasons. Feeding was highly clustered and the main core areas, less than approximately 3 km2 wide, were stable across time of day and season. The majority of the occurrences (86.2%) and feeding groups (94%) were situated in two bay locations - Galveston Ship Channel (GSC) and Bolivar Roads (BRD) - that amounted to only one- fifth of the surveyed area. Compared to conditions in GSC and BRD when no dolphins were sighted, feeding cores weredeeper and more seabirds were observed. This fine-scale study of bottlenose dolphin distribution may contribute to a better understanding of habitat requirements for coastal dolphins. It also may provide information needed to minimize potential negative impacts to this population caused by human activities.

Thesis (M.A.)--University of Hawaii at Manoa, 2004. / Includes bibliographical references (leaves 125-135). / vii, 135 leaves, bound ill. 29 cm