Adult female survival, population trend, and the implications of early primiparity in a capital breeder, the southern elephant seal (Mirounga leonina).

PISTORIUS, P.; BESTER M,; LEWIS, M.; TAYLOR, F.; CAMPAGNA, C. ; KIRKMAN, S.

JOURNAL OF ZOOLOGY

The Zoological Society of London

Año: 2004 vol. 263 p. 107 - 119

0022-5460

Adult female survival as a potential proximate factor responsible for observed changes in southern elephant seal Mirounga leonina populations was investigated. We compared the survival rate estimates from mark?recapturedata for female elephant seals from the Marion Island population (using program MARK) for two periods (pre- andpost-decline) during the past 15 years and with estimates from another population in southern Argentina, whichhad increased steadily during the same period. Survival of prime-age adult females increased significantly by 6.2%during the latter part of the decline at Marion Island, and the survival of adult females at the colony in southern Argentinawas 3.2% greater than at Marion Island after the stabilization.We thereby demonstrated the importance ofadult female survival in population regulation and emphasized the importance of monitoring adult females in order to understand population changes in southern elephant seals. In addition, we investigated whether reproductiveexpenditure early on in life reduces future reproductive potential in the population at Marion Island.We did this by estimating and comparing future survival and breeding probabilities of females primiparous at different ages. Thefuture annual survival and breeding probabilities of females breeding at a young age, was similar to those from females primiparous at an older age. There was also no reduced survival in the year following first breeding in young or older first time breeders. Reproductive expenditure in young primiparous females therefore did not entail future fitness costs relative to older primiparous females, and we found no evidence supporting the existence of various life-history strategies in terms of age of primiparity within a population of southern elephant seals.Mirounga leonina populations was investigated. We compared the survival rate estimates from mark?recapturedata for female elephant seals from the Marion Island population (using program MARK) for two periods (pre- andpost-decline) during the past 15 years and with estimates from another population in southern Argentina, whichhad increased steadily during the same period. Survival of prime-age adult females increased significantly by 6.2%during the latter part of the decline at Marion Island, and the survival of adult females at the colony in southern Argentinawas 3.2% greater than at Marion Island after the stabilization.We thereby demonstrated the importance ofadult female survival in population regulation and emphasized the importance of monitoring adult females in order to understand population changes in southern elephant seals. In addition, we investigated whether reproductiveexpenditure early on in life reduces future reproductive potential in the population at Marion Island.We did this by estimating and comparing future survival and breeding probabilities of females primiparous at different ages. Thefuture annual survival and breeding probabilities of females breeding at a young age, was similar to those from females primiparous at an older age. There was also no reduced survival in the year following first breeding in young or older first time breeders. Reproductive expenditure in young primiparous females therefore did not entail future fitness costs relative to older primiparous females, and we found no evidence supporting the existence of various life-history strategies in terms of age of primiparity within a population of southern elephant seals.