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

dc.contributor.authorJordaan, Rowan Keith
dc.contributor.authorOosthuizen, Wessel Christiaan
dc.contributor.authorReisinger, Ryan Rudolf
dc.contributor.authorDe Bruyn, P.J. Nico
dc.contributor.emailrowan.jordaan@up.ac.zaen_ZA
dc.date.accessioned2021-10-04T11:09:45Z
dc.date.available2021-10-04T11:09:45Z
dc.date.issued2020
dc.description.abstractKiller 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.departmentMammal Research Instituteen_ZA
dc.description.departmentZoology and Entomologyen_ZA
dc.description.librarianam2021en_ZA
dc.description.sponsorshipThe 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.urihttp://www.wildlifebiology.orgen_ZA
dc.identifier.citationJordaan, 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.issn0909-6396 (print)
dc.identifier.issn1903-220X (online)
dc.identifier.other10.2981/wlb.00732
dc.identifier.urihttp://hdl.handle.net/2263/82031
dc.language.isoenen_ZA
dc.publisherNordic Council for Wildlife Researchen_ZA
dc.rights© 2020 University of Pretoria. This is an Open Access article.en_ZA
dc.subjectAbundanceen_ZA
dc.subjectCalving rateen_ZA
dc.subjectDemographyen_ZA
dc.subjectEnvironmental variationen_ZA
dc.subjectFisheriesen_ZA
dc.subjectKiller whale (Orcinus orc)en_ZA
dc.titleAbundance, survival and population growth of killer whales Orcinus orca at subantarctic Marion Islanden_ZA
dc.typeArticleen_ZA

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