Birth demographics of bottlenose dolphins, Tursiops truncatus, in Doubtful Sound, Fiordland, New Zealand -: preliminary findings

Bottlenose dolphins (Tursiops truncatus Montagu) in Doubtful Sound (45degrees30'S, 167degrees00'E), New Zealand, live at the southern extreme of the species' worldwide range. Demographics of this population were observed from 1994 to 1999. Sixteen of 18 live births occurred from December to February. This is a short birthing period for bottlenose dolphins; populations in tropical regions calve during 10-12 months of the year. Nine calves were born to a population of 65 animals in 1999, a birth rate (13.8%) twice that of the average for 1995-97 (5.6%). Average calving interval during the observation period was 3 years (SD = 1.15) with a range of 2-5 years. Apparent survival rate of calves to Year 1 was 80.0%. Birth rate, calving interval, and mortality of calves are comparable to other bottlenose populations worldwide. Parturition appears to become strongly seasonal with increasing latitude in bottlenose dolphin populations.