My research is a part of the South West Marine Research Program (SWMRP) in Bunbury, Western Australia. For a section of my thesis, I investigated if there were sex-specific differences in home ranges and abundance patterns of the local Indo-Pacific bottlenose dolphin population. To answer these questions we conducted year-round, boat-based, photo-identification surveys from 2007 through 2013.
Our interest in home ranges was partly sparked through the variation in bottlenose dolphin home range characteristics across geographic locations. We wanted to explore if males and females shared similar home ranges, like some bottlenose populations, or if males range further than females, like in Sarasota Bay. To analyse our data, we applied a new approach that accounted for absolute barriers such as land, and performed analyses on dolphins that were sighted ≥ 30 times, were of known sex and were within the adult age class throughout the duration of the study. Results indicated that adult males had a 99% probability of having larger home ranges than adult females, helping explain population dynamics.
Considering that males had larger home ranges than females, we then wanted to find out if the abundance estimates differed between the sexes. We therefore applied separate male and female abundance models, and found that the abundance estimates and temporary emigration rates for males and females differed and both were seasonally dependent. We found that during the warmer months, both males and females showed an increase in abundance, coinciding with the peak breeding season.
Our research would not have been possible if it was not for the
help from our dedicated assistants and funding bodies for the SWMRP: the Dolphin Discovery Centre, Bemax Cable Sands, BHP Billiton Worsley Alumina, Bunbury Port Authority, City of Bunbury, Cristal Global, Department of Environment and Conservation, Iluka, Millard Marine, Naturaliste Charters, Newmont Boddington Gold, South West Development Commission and WAPRES.
This article was published on page in the November 2014 issue of Nicks n Notches