No abstract

The social structure of coastal ecotype bottlenose dolphins, Tursiops truncatus, is largely unknown as they inhabit regions far from shore. This study reports on a community of bottlenose dolphins ≥ 27 km from Grand Bahama Island (May‐September, 1993–2002). Resident and non‐resident dolphins occurred in the area. Some dolphins traveled over 320 km between communities; others showed long‐ term site fidelity up to 17 yr. Average group size was 3–5, and was significantly larger with calves present and significantly smaller when traveling. The half‐weight index was used to determine coefficients of association (COA) for individuals of known sex annually and for pooled years. Permutation tests revealed non‐random associations and presence of preferred/avoided companions in all data sets. Annual COAs were low: female‐female χ= 0.31, male‐male χ= 0.30, and mixed‐sex χ= 0.26. Mother‐calf associations showed the highest values. Some males formed strong, long‐term bonds. Female COAs fluctuated with reproductive status. Using pooled data, COAs were lower and the same basic trends were evident. However, strong associations seen in the annual data were not evident in pooled data. Bottlenose dolphins that inhabit offshore, shallow water show many of the same social structure characteristics as in well‐studied coastal populations.

No abstract

No abstract

Atlantic bottlenose dolphins (Tursiops truncatus)are frequently observed in the coastal waters of Palm Beach County, Florida. In this study, mark-recapture surveys using photo-identification techniques were used to estimate population abundance of Atlantic bottlenose dolphins in this area for the first time. Surveys were conducted for 11 years, between 2005 and 2016, during which 384 individuals were identified and catalogued from distinctive nicks and notches on their dorsal fins. Each marked individual was documented an average of 2.4 times (range 1 to 19). Low resighting rates and a constant rate of encounter with previously unmarked individuals suggest that the population is open, comprising both residents and transients. The Jolly-Seber method was used to estimate population abundance. Estimates of abundance varied greatly in time with an overall average of 264 individuals and a 95% confidence interval of 162 to 366 (SE = 51.3), indicating a variable population size. As threats in the region continue to rise, such as overfishing, toxic algae blooms, and environmental pollutants, this understudied population may be vulnerable to decline. A better understanding of the population dynamics could facilitate more effective conservation action.