Ranging and diving behaviour of two ‘offshore’ bottlenose dolphins, Tursiops sp., off eastern Australia

Abstract

This paper describes a study of the ranging and diving behaviour of two ‘offshore’ bottlenose dolphins, Tursiops sp., in the waters off south-east Queensland, determined using satellite-linked time-depth recorders attached to two animals. Animal 1's tag transmitted for 30 days, Animal 2's for 143 days. Immediately after tagging, Animal 1 swam south, reaching a point 146 km south of the point of tagging, then swam generally northwards until the tag ceased working. Animal 2's observed range covered 778 km², with a core area of 86 km². The greatest north–south distance between all locations for Animal 2 was 43 km. The manner in which maximum dive depth was related to dive duration was analysed using constrained principal curves. These analyses indicated that for both animals, short dives were to less than 5 m, and there was no clear relationship between dives of greater duration and depth. These dolphins appear to behave differently from ‘offshore’ bottlenose dolphins studied elsewhere.