Age distribution of breeding female Antarctic fur seals in relation to changes in population growth rate

I. L. Boyd, N. J. Lunn, P. Rothery, J. P. Croxall

Research output: Contribution to journalArticlepeer-review

Abstract

The age distribution of breeding female Arctocephalus gazella at Bird Island, South Georgia, in 1988 was compared with the age distribution of a sample obtained in 1971-1973. The mean age in 1971-1973 was 7.41 (SE 0.26) yr and in 1988 it was 6.93 (SE 0.20) yr. After correction for age-dependent arrival time at the pupping beach in 1988, the mean age was 6.22 (SE 0.14) yr, which was significantly lower than in 1971-1973. Indicators of population size suggested that population growth at Bird Island had declined to <3% annually by 1988 compared with rapid growth (17%) in 1958-1972. Exponential models fitted to the frequency distribution of age-classes >5 yr and corrected for the rate of increase of the population gave adult survival rates of 0.66 (SE 0.03) and 0.88 (SE 0.02) for the 1988 and 1971-1973 samples, respectively. The reduced apparent adult survival rate in the 1988 sample was probably caused by emigration brought about by high densities of females on the pupping beaches. There are few signs that the fur seal population at South Georgia is close to carrying capacity. -Authors

Original languageEnglish
Pages (from-to)2209-2213
Number of pages5
JournalCanadian Journal of Zoology
Volume68
Issue number10
DOIs
Publication statusPublished - 1990

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