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RESEARCH ARTICLE
Contents Vol 54(1)

Maternal strategies of the New Zealand fur seal: evidence for interannual variability in provisioning and pup growth strategies

Simon D. Goldsworthy
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South Australian Research and Development Institute (SARDI) – Aquatic Sciences, 2 Hamra Avenue, West Beach, SA 5024, Australia. Email: goldsworthy.simon@saugov.sa.gov.au

Australian Journal of Zoology 54(1) 31-44 https://doi.org/10.1071/ZO05041
Submitted: 8 August 2005  Accepted: 5 January 2006   Published: 23 March 2006

Abstract

Maternal attendance, nursing behaviour, pup growth and weaning age were investigated in the New Zealand fur seal (Arctocephalus forsteri) at Kangaroo Island, South Australia. Foraging trips to sea increased throughout lactation (5.9–9.8 days), while the duration of shore attendance bouts (1.7 ± 0.7 days) remained unchanged, resulting in time ashore declining from 24% to 14% throughout lactation. Mothers with sons made longer foraging trips than mothers with daughters throughout lactation and, as a consequence, maternal time ashore was less for sons (21%) than for daughters (28%). Pups maintained an overall sucking-rate of 1.4 h day–1 throughout their mothers’ lactation, by sucking more frequently and for longer periods as their mother became less available. Because mothers with daughters were ashore more frequently, the overall sucking-rate of females (1.7 h day–1) was greater than that of male pups (1.1 h day–1). The growth patterns of male and female pups from two cohorts were similar, but males grew faster and weaned heavier in one of the years. Age at weaning was ~285 days (9.4 months). This study indicates some significant differences in the nature of maternal expenditure in male and female pups, and the growth strategies used by pups both within and between years.


Acknowledgments

I am indebted to the many volunteers who assisted in the field, and to staff of the National Parks and Wildlife Service on Kangaroo Island, particularly to Terry Dennis and Anthony Maguire. The manuscript was improved by comments from John Arnould, Ian Boyd, Rob Harcourt, Mark Hindell, Mary-Anne Lea, Tony Lee and Peter Shaughnessy. Mike Cullen, Gerry Quinn and Mark Hindell provided statistical advice. The following provided financial support for this project: the Wildlife Conservation Fund – South Australia, CSIRO/Monash Collaborative Research Fund, CSIRO Institute for Natural Resources and the Environment Post-graduate Project Award, Australian National Parks and Wildlife Service, the M.A. Ingram Trust, the Victorian Institute for Marine Sciences and the Museum of Victoria. All animal procedures were undertaken with approval from the South Australian Parks and Wildlife Service (Permit number SA-89024).


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