Median pupping date, pup mortality and sex ratio of fur seals at Marion Island

Show simple item record Hofmeyr, G.J. Greg (Gordon John Gregory) Bester, Marthan Nieuwoudt Pistorius, Pierre Anton Mulaudzi, Tambu W. De Bruyn, P.J. Nico Ramunasi, Justice A. Tshithabane, Hendrik N. McIntyre, Trevor Radzilani, Phathu M. 2008-06-02T13:34:38Z 2008-06-02T13:34:38Z 2007
dc.description.abstract Modelling fur seal populations requires the accurate assessment of demographic parameters such as age-specific mortality. Owing to the highly variable mortality rates that pups are subject to, mortality of this age class is perhaps the most important factor determining the number of surviving individuals within each cohort. Early pup mortality,sex ratio and median pupping date were determined for sympatric populations of Subantarctic fur seals (Arctocephalus tropicalis) and Antarctic fur seals (A. gazella) at Marion Island, Southern Ocean. Mortality for this species was density dependent, varying from 0.8% at low density sites to 10.9% at high density sites. More accurate methods employed at low-density sites showed a substantially higher pup mortality at three weeks of 1.3-3.4% for Subantarctic fur seals. The same method yielded a mortality estimate at four weeks of age of 1.1-5.1% for Antarctic fur seals. Despite the underestimate inherent in island-wide counts for Subantarctic fur seals, these estimates are still useful for observing temporal and spatial patterns. Sex ratios were at parity for newborns of both species. The sex ratio of eightweek-old Subantarctic fur seal pups was also at parity, which is unusual for fur seal populations. The median pupping dates determined for Subantarctic fur seals and Antarctic fur seals did not differ substantially from previous estimates. en
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dc.identifier.citation Hofmeyr, GJG, Bester, MN, Pistorius, PA, Mulaudzi, TW, De Bruyn, PJN, Ramunasi, JA, Tshithabane, HN, McIntyre, T & Radzilani, PM 2007, 'Median pupping date, pup mortality and sex ratio of fur seals at Marion Island', South African Journal of Wildlife Research, vol. 37, no. 1, pp. 1-8. [] en
dc.identifier.issn 0379-4369
dc.language.iso en en
dc.publisher Southern African Wildlife Management Association en
dc.rights Southern African Wildlife Management Association en
dc.subject Arctocephalus gazella en
dc.subject Arctocephalus tropicalis en
dc.subject Density dependence en
dc.subject Marion Island en
dc.subject Median pupping date en
dc.subject Mortality en
dc.subject Sex ratio en
dc.subject Southern Ocean en
dc.subject.lcsh Puppies
dc.subject.lcsh Mortality
dc.subject.lcsh Sex ratio
dc.title Median pupping date, pup mortality and sex ratio of fur seals at Marion Island en
dc.type Article en

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