Polar Biology

, Volume 24, Issue 5, pp 343–348

Temporal changes in fecundity and age at sexual maturity of southern elephant seals at Marion Island

  • P.A. Pistorius
  • M.N. Bester
  • S.P. Kirkman
  • F.E. Taylor
Original Paper

DOI: 10.1007/s003000000217

Cite this article as:
Pistorius, P., Bester, M., Kirkman, S. et al. Polar Biol (2001) 24: 343. doi:10.1007/s003000000217

Abstract.

Our objective was to examine the effect of variation in reproductive parameters on the demography of southern elephant seals at Marion Island. We used age-specific capture probabilities of breeding females in a Cormack-Jolly-Seber context to derive reproductive rates. We found that age at maturity declined and fecundity rates increased as the population declined, indicating a compensatory response. Fecundity rates ranged from 0.03 to 0.29 among 3-year-olds (mean=0.16), 0.18 to 0.50 in 4-year-olds (mean=0.40), and 0.28 to 0.50 in 5-year-olds (mean=0.45). We think that a relative increase in food availability, concomitant with the population decline, promoted earlier sexual maturity correlated with more rapid growth of juveniles when population abundance was lower. It is suggested that the relative importance of fecundity in population regulation in elephant seals has been underestimated. Moreover, it appears that the onset of sexual maturity may be the first demographic variable to change in response to a change in population density.

Copyright information

© Springer-Verlag 2001

Authors and Affiliations

  • P.A. Pistorius
    • 1
  • M.N. Bester
    • 1
  • S.P. Kirkman
    • 1
  • F.E. Taylor
    • 1
  1. 1.Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa