Evolution of the population of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in the Cockburn Sound, Perth, Western Australia, from 1993 to 2013

Supervisor: Lars Bejder (Cetacean Research Unit, Centre for Fish, Fisheries and Aquatic Ecosystem Research, Murdoch University, Western Australia)
Indo-Pacific bottlenose dolphins (Tursiops aduncus) inhabite the Cockburn Sound, an inlet on the coast, south of Perth, Western Australia. Since decades, the Cockburn Sound has been subject to human activities inducing habitat change, and direct human-dolphin interactions, such as illegal provisioning, have been reported. Four different boat-based researches have been conducted since 1993. Using photoidentification, ~200 individuals were identified in 1993-7 (n = 246 surveys), 191 individuals in 2000-3 (n =221 surveys), and 158 individuals in 2008 (n = 37 surveys) within the Cockburn Sound. Since 2011, 41 days of survey were conducted in the Cockburn Sound and a total of 118 individuals were observed (65 adults, 12 adults/sub-adults, 16 sub-adults and 25 calves). From them, 39 individuals were confirmed to be present from 2008, including 3 from 2000-3 and 21 individuals from 1993-7. Findings suggest that there were considerable changes in the population structure since 1993 and a decline of the number of individuals in the population due to 1) direct and indirect human-dolphins interactions; and/or 2) an underestimation of the population. Results also demonstrated that dolphins conditioned to food provisioning could increase their home range, change their association patterns and increase also their risk of injuries. This study shows the interest to have a sustainable balance between human and bottlenose dolphins needs and the value of long-term studies to well define appropriate management toward the conservation of the Indo-pacific bottlenose dolphin population inhabiting the Cockburn Sound.

Keywords: bottlenose dolphin, Tursiops aduncus, photo-identification, population, human-dolphin interactions, provisioning, conservation