Growth, Sexual Maturity and Food-Intake of Australian Indian-Ocean Bottle-Nosed Dolphins, Tursiops-Truncatus, in Captivity

Abstract

Body size and food intake of four female and three male captive Indian Ocean bottlenose dolphins, Tursiops truncatus, were recorded regularly over a 10-year period. Growth of three captive-born female calves was also recorded. Growth of females parallelled that of South African bottlenose dolphins, tending toward an asymptote of c. 240 cm at 16 years of age. Growth of males was characterised by a secondary growth spurt at puberty between the ages of 10 and 12 years. Wild-caught females were approximately 10% heavier for age than their South African conspecifics. The captive-born females were up to 50% heavier than their African counterparts. Growth rates of females and males were 2.1-2.6 cm per year and 2.0-2.6 cm per year, respectively, between the ages of 3 and 16 years. Females were known to be reproductively mature at 11-13 years of age when lengths were between 227 and 238 cm. DNA fingerprinting of offspring and potential parents revealed that one of the three males was reproductively mature at 233 cm and another at either 222 or 226 cm. One of the males was sexually mature at the beginning of its secondary growth spurt at 10 or 11 years of age. Food intake of dolphins increased significantly with decreasing water temperature. It is suggested that variations in water temperature and food availability may play a role in governing body-size differences between T. truncatus populations.