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Age and reproductive maturity of New Zealand fur seals (Arctocephalus forsteri) in southern Australia


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McKenzie, J, Page, B, Shaughnessy, PD and Hindell, MA 2007 , 'Age and reproductive maturity of New Zealand fur seals (Arctocephalus forsteri) in southern Australia' , Journal of Mammalogy, vol. 88, no. 3 , pp. 639-648 , doi: 10.1644/06-MAMM-A-150R1.1.

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New Zealand fur seals (Arctocephalus forsteri) are common in the Australian-New Zealand region, but vital
demographic data are lacking. Accurate determination of the age of individuals is critical to the study of agespecific
life-history parameters. A cross-sectional sample of female and male New Zealand fur seals was caught
and animals were individually marked on Kangaroo Island, South Australia, between 2000 and 2003. Seals were
aged through examination of a postcanine tooth, which was removed from each animal. Annual formation of
cementum layers was confirmed and accuracy in age estimation was determined by examination of teeth removed
from individuals of known age. Indirect methods of assessing reproductive maturity based on characteristics of
mammary teats indicated that females 1st gave birth between 4 and 8 years of age, with an average age at reproductive
maturity (ARM) of 5 years. No females were observed to breed beyond 22 years. Age of 1st territory
tenure in males ranged from 8 to 10 years. Variation in ARM between individuals appears to be related in part to
body size and condition. Classification of mammary teat status in combination with techniques for aging live
animals provided a means of assessing ARM in the absence of extensive longitudinal data.

Item Type: Article
Authors/Creators:McKenzie, J and Page, B and Shaughnessy, PD and Hindell, MA
Keywords: age estimation, Arctocephalus forsteri, cementum, longevity, reproduction
Journal or Publication Title: Journal of Mammalogy
Publisher: Allen Press
ISSN: 0022-2372
DOI / ID Number: 10.1644/06-MAMM-A-150R1.1
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