ESR 32:71-88 (2017)  -  DOI: https://doi.org/10.3354/esr00784

Demographic characteristics of Australian humpback dolphins reveal important habitat toward the southwestern limit of their range

Tim N. Hunt1,*, Lars Bejder2, Simon J. Allen3, Robert W. Rankin2, Daniella Hanf1, Guido J. Parra1

1Cetacean Ecology, Behaviour and Evolution Lab, School of Biological Sciences, Flinders University, Sturt Road, Adelaide, SA 5042, Australia
2Cetacean Research Unit, School of Veterinary and Life Sciences, Murdoch University, South Street, Perth, WA 6150, Australia
3Centre for Marine Futures, School of Biological Sciences and Oceans Institute, University of Western Australia, Stirling Highway, Perth, WA 6009, Australia
*Corresponding author:

ABSTRACT: The paucity of information on the recently described Australian humpback dolphin Sousa sahulensis has hindered assessment of its conservation status. Here, we applied capture-recapture models to photo-identification data collected during boat-based surveys between 2013 and 2015 to estimate the abundance, site fidelity and residence patterns of Australian humpback dolphins around the North West Cape (NWC), Western Australia. Using Pollock’s closed robust design, abundance estimates varied from 65 to 102 individuals, and POPAN open modelling yielded a super-population size of 129 individuals in the 130 km2 study area. At approximately 1 humpback dolphin per km2, this density is the highest recorded for this species. Temporary emigration was Markovian, suggesting seasonal movement in and out of the study area. Hierarchical clustering showed that 63% of individuals identified exhibited high levels of site fidelity. Analysis of lagged identification rates indicated dolphins use the study area regularly, following a movement model characterised by emigration and re-immigration. These density, site fidelity and residence patterns indicate that the NWC is an important habitat toward the southwestern limit of this species’ range. Much of the NWC study area lies within a Marine Protected Area, offering a regulatory framework on which to base the management of human activities with the potential to impact this threatened species. Our methods provide a methodological framework to be used in future environmental impact assessments, and our findings represent a baseline from which to develop long-term studies to gain a more complete understanding of Australian humpback dolphin population dynamics.


KEY WORDS: Sousa sahulensis · Abundance · Survival · Emigration · Capture-recapture · Site fidelity · Residency


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Cite this article as: Hunt TN, Bejder L, Allen SJ, Rankin RW, Hanf D, Parra GJ (2017) Demographic characteristics of Australian humpback dolphins reveal important habitat toward the southwestern limit of their range. Endang Species Res 32:71-88. https://doi.org/10.3354/esr00784

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