Annual cycle of the southern elephant seal Mirounga leonina (Linn.) at Marion Island

Abstract

The annual cycle of southern elephant seals, Mirounga leonina, was studied at Marion Island (46°54'S, 37°45' E), between August 1973 and December 1976. Data on the breeding and moulting haul-out of different age and sex classes were obtained by conducting once weekly censuses in a selected study area. The haul-out sequence, characterized by a high degree of synchronization and annual regularity was similar to that occurring at other breeding grounds. Photoperiod, in particular the mean monthly increase in day length, appeared to act as an obligatory proximate factor initiating the haul-out to breed and onset of hair growth. Temperature and radiation appeared to act as obligatory ultimate factors initiating the haul-out to moult.