Heaviside‟s dolphins, Cephalorhynchus heavisidii, are among the least known cetaceans. They are endemic to the coastal waters along the west coast of southern Africa. The occurrence, behaviour and group dynamics were investigated for these dolphins in Table Bay, South Africa during the summer of 2008 and 2009. Markrecapture photographic identification techniques, modelling techniques and Geographical Information System (GIS) were used to analyse the data. The dolphins were observed primarily in a well-defined 7 km2 area on the south side of Table Bay along a 3 km east-west stretch of coast known as Granger Bay, and within 2 km from shore. They used this area heterogeneously; for the array of behaviours observed, all core areas (50 % kernels) were located in Granger Bay with very little overlap of areas used for milling, socialising, resting and travelling. Milling and socialising were exhibited more often than travelling and resting. Foraging was never observed in areas close to shore, which supports earlier studies suggesting that these dolphins forage primarily offshore. Of the 95 identified individuals, 24.2 % of the individuals were seen only once and 73.7 % of the individuals were sighted less than five times while two individuals were seen 11 times. Groups varied in size from one to 26 animals with a median of five animals. Many of the potential dyads were never seen and those observed had generally weak measure of association. The group structure appears highly dynamic, with great lability in group sizes and membership, suggesting a fluid social system with mostly weak inter-individual bonds. Individuals in Table Bay display low site fidelity, at least in the short-term. The observed pattern of area use and behavioural preferences indicate that coastal management strategies should consider the ecological and behavioural needs of Heaviside's dolphins to appropriately safeguard this species as a valuable component of South African natural treasures and legally protected taxa. Further continuing research is needed to build on this initial study to better understand the processes that shape the population structure and group dynamics of Heaviside's dolphins, and to provide further detail on habitat preferences and areas used, both in Table Bay and environs. / Dissertation (MSc)--University of Pretoria, 2011. / Zoology and Entomology / Unrestricted

Heaviside's dolphin (Cephalorhynchus heavisidii) is a poorly studied coastal delphinid with a limited inshore distribution off the west coast of southern Africa where it is sympatric with the similar sized dusky dolphin (Lagenorhynchus obscurus). It is exposed to an unknown level of bycatch particularly in near-shore set-net fisheries and is also potentially impacted by the growing boat-based whale watching industry in South Africa. In this thesis I describe the results of a study investigating the distribution, movements, behaviour and abundance of Heaviside's dolphins in the near-shore environment of the Western Cape of South Africa as a precursor to assessing its potential vulnerability to anthropogenic threats. Data were gathered using three different approaches in the field; diurnal shore based observations, boat based photo-ID surveys along ~390 km of coastline and satellite telemetry. Data were collected for dusky dolphins where feasible. Heaviside’s dolphins exhibited a strong pattern of resting inshore during daytime and foraging offshore at night that was presumed to be related to the movement of juvenile hake (Merluccius capensis) closer to the surface at night. In addition, despite near-shore observations failing to indicate feeding, dolphins were consistently found to be more abundant along regions of the coast which over the long term had higher levels of small hake available offshore. In contrast the near-shore distribution of dusky dolphins varied considerably between years possibly due to the very near-shore environment being at the edge of their habitat. A tendency for dusky dolphins to move offshore during upwelling conditions was observed from shore in St Helena Bay, the site of a strong predictable upwelling cell. However this was the only location in which very large groups of animals (50-500) were seen during coastal boat surveys suggesting this pattern may have been area specific and feeding strategies may vary throughout their range. Sympatric appears to be mediated by differences in overall range and prey type and size differentiation. Heaviside’s dolphins were found to have small home ranges and show a high degree of site fidelity over several years, at least during summer months. Dolphins fitted with satellitelinked transmitters used only limited home ranges (~876 to 1990 km2) which scaled positively with body size within the ~50 day tracking period, while photographically identified animals did not disperse significantly further than this over 3 years. The maximum coastwise displacement observed for an individual (88.4 km after 1 year) was considerably less than the 390 km length of the overall study area, and equivalent to the maximum coastwise movement seen during satellite-tagging (83.1 km). This suggests that measured home ranges may be stable over several years, although the number of resighted individuals (n = 76) was small and (as data collection was restricted to summer months) seasonal differences in movements or migrations cannot be ruled out. Associations among photographically identified animals did not differ from a random mixing of individuals, suggesting that this species has a fission-fusion type social structure at least over the short term. The abundance of Heaviside's dolphins was calculated from photo-ID mark-recapture data at three spatial scales using Chapman’s modified Petersen estimators. The proportion ofdistinctively marked individuals in this species is low (14 - 17%) reducing sample sizes and introducing a large extrapolation factor, both of which contribute to an increase in the variance of any resultant population estimate. Using resightings after one year, the total number of animals over the whole 390km study area was calculated to be 6345 (CV = 0.26, CI = 3573 – 11 267) while using same-season re-sightings the total number of animals using a 20km long section of coastline in the centre of the study area was calculated as 527 (CV = 0.35, CI = 272 – 1020). These estimates may be significantly biased downwards by the effects of heterogeneity in the capture probability of individuals which it was not possible to account for analytically due to small sample sizes. Sympatry of Heaviside's and dusky dolphins appears to be mediated by differences in the overall range and in the type and size of prey consumed. From a conservation point of view, our findings for Heaviside's dolphins are encouraging in that they indicate a relatively large population size, although their strong site fidelity does make them more vulnerable to localised impacts than a more widely ranging species like dusky dolphins and this needs to be considered during management of the population. / Thesis (PhD)--University of Pretoria, 2009. / Zoology and Entomology / unrestricted