Bunbury is located approximately 170km south of Perth and is the fastest growing regional center in Australia.
Its waters are home to a population of Indo-Pacific bottlenose dolphins (Tursiops aduncus) that MUCRU researchers have been studying since 2007.
The local dolphin population is subject to increasing pressures as the city expands, including coastal development, increased shipping, targeted boat-based dolphin tourism and a general increase in human activities on the water, e.g., fishing and boating. This has resulted in increased threats, such as entanglement in fishing gear, vessel strikes, poor water quality and illegal food-provisioning. The local dolphin population has also recently experienced an unusual mortality event. It is therefore important to continue long-term data collection to inform management and industry to minimize human impacts on the population.
For my PhD, I am focusing on population dynamics and predictive habitat modelling of the dolphin population. Along with my assistants, I conduct year-round boat-based photo identification surveys. Our study area covers 520 km2 and it is divided into six zones that extend 10 km2 offshore. Over the past 18 months, I have conducted 164 surveys and encountered 374 dolphin groups where we have catalogued more than 440 individuals.
To investigate the abundance of the Bunbury dolphin population, the survey has been designed to allow input into Pollock’s Robust Design model, which takes into account the temporary immigration of animals. Previous research by Dr. Holly Raudino (nee Smith) estimated that the abundance reached a high of about 139 individuals in autumn, whereas it dropped to a low of about 65 individuals in winter. I aim to further explore this trend by determining the seasonal abundance for adult females and males separately. To date, we have over 230 confirmed sexes through either DNA biopsy sampling, viewing of the genital area or the presence of a calf consistently in baby position.
The lower abundance of dolphins in the study area during winter might be explained by seasonal differences in adult male ranging patterns. We have recently expanded the study area, in order to investigate the seasonal movements and home ranges of dolphins, particularly of adult males. Excitingly, in winter 2012 we sighted adult males up to 10km offshore in deeper and warmer waters.
It appears that adult male dolphin home ranges differ from females and the use of their environment changes seasonally. Generally, dolphin habitat preferences are influenced by the physical environment, food availability, protection from predators and suitability as a calving ground. Documenting critical areas and exploring factors that may influence habitat use are important for conservation and management efforts. Before analysing data, in 2013 I will be attending Duke University to receive training in habitat modelling. My field work will also be finalized in 2013 and I aim to submit my thesis in 2014.
This research is made possible through funding from the South West Marine Research Program’s non-profit and industry partners, including, 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 pages 22-23 in the January 2013 Nicks n Notches.