arnould-influencesonfecundity-2010.pdf (150.9 kB)
Influences on fecundity in Australian fur seals (Arctocephalus pusillus doriferus)
journal contribution
posted on 2010-04-01, 00:00 authored by J Gibbens, L Parry, John ArnouldJohn ArnouldRecovery of the Australian fur seal (Arctocephalus pusillus doriferus) population has been slower than that of other fur seals, perhaps due to nutritional constraints on fecundity. However, the population doubled in recent decades, suggesting that reproductive rates may have changed. Pregnancy rates and birthrates were estimated and the influences of maternal age, size, condition, and lactation status were investigated over 3 consecutive breeding seasons (2003–2005). Mid-gestation pregnancy rate, estimated from plasma progesterone concentrations, was 84% ± 3% (mean ± SE) and was negatively influenced only by age (P< 0.001). Birthrate, estimated from observations of females with newborn offspring during the breeding season, was 53% 6 3% (mean ± SE) and was influenced negatively by lactation status (P = 0.035). The difference between pregnancy rates and birthrates suggests that a high degree of late-gestation abortion occurs, especially in younger females. Lactation status was not influenced by any variables, and the high rate (86% ± 2%; mean ± SE) suggests that many offspring are suckled beyond the typical weaning period. Although relationships between reproductive rates and body condition were not found, the results are consistent with a nutritional stress hypothesis. The recent increase in population growth is not due to increased fecundity, which remains low compared to other otariids. Paradoxically, high pregnancy rates were observed in young females (3 years), suggesting that rapid maturity is adaptive for benthic foragers.
History
Journal
Journal of mammalogyVolume
91Issue
2Pagination
510 - 518Publisher
American Society of MammalogistsLocation
Lawrence, Kan.Publisher DOI
ISSN
0022-2372eISSN
1545-1542Language
engPublication classification
C1 Refereed article in a scholarly journalCopyright notice
2010, American Society of MammalogistsUsage metrics
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