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

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Hunt, Tim M
Bejder, L
Allen, Simon
Rankin, R W
Hanf, Damiella
Parra, Guido Jose
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Inter Research
© The authors 2017.
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The authors
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.
Open Access under Creative Commons by Attribution Licence. Use, distribution and reproduction are un-restricted. Authors and original publication must be credited.
Sousa sahulensis, Abundance, Survival, Emigration, Capture-recapture, Site fidelity, Residency
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.