Behavioral Ecology and Sociobiology

, Volume 55, Issue 4, pp 349–362 | Cite as

Harem choice and breeding experience of female southern elephant seals influence offspring survival

  • Clive R. McMahon
  • Corey J. A. BradshawEmail author
Original Article


Female mammals can increase their lifetime fitness through modification of investment potential and by providing better rearing environments with improved breeding experience. We examined the relationships between reproductive fitness and the behavioural decisions that female southern elephant seals (Mirounga leonina) made during the breeding season. We examined whether mother age and breeding experience influenced reproductive success (measured as 1st-year survival probability), and whether there was a change in the choice of harem size with increasing age. Pups produced by young mothers had lower 1st-year survival probability than pups produced by older mothers. A significant increase in mean female mass with age required an analysis of both these effects on offspring survival. There was a significant positive effect of both female age and mass, and the interaction between the two, on 1st-year pup survival. The proportion of young mothers (<5 years old) decreased and the proportion of older mothers (>6 years old) increased with increasing harem size (harems surveyed from 1997 to 2001). Females chose larger harems in which to breed as they aged. Females demonstrated fidelity to breeding areas among successive breeding seasons, with older females displaying greater breeding-site fidelity than younger females. The mean number of previous breeding attempts per female within a harem (breeding experience) increased significantly with increasing harem size. Breeding females returned to breed later in the breeding season as they aged—we hypothesize that young, subordinate females gain a priority advantage by returning earlier. These results lend support to the hypothesis that there are fitness advantages, in terms of offspring survival, that are conferred to females that breed in successively larger harems with age. Potential mechanisms that select for females to improve their breeding conditions include improved mate selection and the avoidance of conspecific harassment in harems.


Reproductive success Mirounga leonina Pup survival Harem size Harem density 



This study was supported by the Antarctic Scientific Advisory Committee (ASAC), an Australian Research Council (ARC) Australian Postdoctoral Fellowship, a Natural Science and Engineering Research Council of Canada (NSERC) Postdoctoral Fellowship and a Sea World Research and Rescue Foundation grant to C.J.A.B. We are indebted to our colleagues of the 50th, 51st, 52nd, 53rd and 54th Australian Antarctic Research Expeditions (ANARE) to Macquarie Island who so ably assisted us in the field by marking seals and collecting resights in often miserable conditions. In particular, we thank H. Burton for his foresight in initiating the demographic program. R. Harcourt, M. Hindell, I. Field, K. Wertz and K. Wheatley provided helpful and insightful comments during writing of the manuscript. We also thank the Associate Editor, F. Trillmich, J. Reiter and an anonymous referee for helpful comments to improve the manuscript.


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Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  1. 1.Antarctic Wildlife Research Unit, School of ZoologyUniversity of TasmaniaHobartAustralia
  2. 2.Australian Antarctic DivisionKingstonAustralia
  3. 3.Antarctic Wildlife Research Unit, School of ZoologyUniversity of TasmaniaHobartAustralia

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