Abundance, survival and population growth of killer whales Orcinus orca at subantarctic Marion Island

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dc.contributor.author Jordaan, Rowan Keith
dc.contributor.author Oosthuizen, W.C. (Wessel Christiaan)
dc.contributor.author Reisinger, Ryan Rudolf
dc.contributor.author De Bruyn, P.J. Nico
dc.date.accessioned 2021-10-04T11:09:45Z
dc.date.available 2021-10-04T11:09:45Z
dc.date.issued 2020
dc.description.abstract Killer whales, Orcinus orca, are a cosmopolitan species with large ecological and demographic variation across populations. Population-specific demographic studies are, therefore, crucial in accurately assessing the status and trends of local killer whale populations. Such studies require long-term datasets and remain scarce, particularly in the Southern Ocean where detailed population specific studies have only been conducted at a single archipelago – Îles Crozet. Here, we analysed 12 years of capture–recapture data (comprising nearly 90 000 identification photographs taken from 2006 to 2018) of killer whales at subantarctic Marion Island (46°54′S, 37°45′E) to estimate the abundance, survival and growth rate of this population. Demographic parameters were estimated using multistate capture recapture models, and Pradel Survival-Lambda and POPAN single-state models implemented in the program MARK. Annual survival probability (0.98 [95% CI: 0.96–0.99]) was constant over time, and no important differences between sexes and age-classes (calves, juveniles, adults) were found. This estimate of survival suggests a life expectancy of approximately 48 years. Realised mean population growth rate (λ) was 1.012 (0.987–1.037) with an estimated population size of 54 (54–60) individuals and a mean calving rate of 0.13 (0.06–0.20) calves born per year per reproductive female. The survival and reproduction rates of killer whales at Marion Island are similar to those of killer whale populations in the eastern North Pacific, Norway and Îles Crozet. However, subtle differences in survival and reproduction rates are present. These are likely the result of local differences in resource abundances, historical impacts on social structure and/or stressors. Also, the presence and scale of fisheries (legal and illegal) in the area may provide opportunities for direct interactions with fishing activities impacting survival and reproduction rates. en_ZA
dc.description.department Mammal Research Institute en_ZA
dc.description.department Zoology and Entomology en_ZA
dc.description.librarian am2021 en_ZA
dc.description.sponsorship The Department of Science and Innovation (DSI) by the National Research Foundations’ SANAP and Thuthuka Funding instruments; the International Whaling Commission Southern Ocean Research Partnership; the Mohamed bin Zayed Species Conservation Fundand by a FILAMO Mobility grant. en_ZA
dc.description.uri http://www.wildlifebiology.org en_ZA
dc.identifier.citation Jordaan, R.K., Oosthuizen, W.C., Reisinger, R.R. et al. 2020, 'Abundance, survival and population growth of killer whales Orcinus orca at subantarctic Marion Island', Wildlife Biology, vol. 2020, no. 4, pp. 1-10. en_ZA
dc.identifier.issn 0909-6396 (print)
dc.identifier.issn 1903-220X (online)
dc.identifier.other 10.2981/wlb.00732
dc.identifier.uri http://hdl.handle.net/2263/82031
dc.language.iso en en_ZA
dc.publisher Nordic Council for Wildlife Research en_ZA
dc.rights © 2020 University of Pretoria. This is an Open Access article. en_ZA
dc.subject Abundance en_ZA
dc.subject Calving rate en_ZA
dc.subject Demography en_ZA
dc.subject Environmental variation en_ZA
dc.subject Fisheries en_ZA
dc.subject Killer whale (Orcinus orc) en_ZA
dc.title Abundance, survival and population growth of killer whales Orcinus orca at subantarctic Marion Island en_ZA
dc.type Article en_ZA


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