Age-specific growth, survival, and population dynamics of female Australian fur seals

Abstract

Postsealing population recovery rates of fur seals and sea lions have differed markedly, perhaps owing to habitat type. Australian fur seals ( Arctocephalus pusillus doriferus Wood Jones, 1925) employ a benthic foraging mode similar to sea lions, and have exhibited similarly slow population recovery. Nonetheless, the population doubled in recent decades, suggesting a recent change in demographic rates. In the present study, the frequency and size of known-age females (n = 297) were used to create body growth and survivorship models. These were compared with models obtained in the 1970s before the recent population increase. Body growth, which is relatively rapid in comparison to other fur seal species, remains unchanged since the 1970s, suggesting that density-dependent effects are absent despite the population increases. Adult survival rates (weighted mean: 0.885) have increased greatly since the 1970s and are the likely mechanism of the recent increases. Total population abundance was estimated to be 4.5 times that of pups. Australian fur seals display high survivorship, rapid body growth, low fecundity, and low population growth rates; all are characteristics typical of benthic foraging sea lions rather than other fur seals.