Abstract:
Life history theory predicts a change in reproduction success with age as energy
resources are limited and must be allocated effectively to maximise reproduction and
survival. In this study we use three reproductive performance measures; maternal
expenditure, offspring weaning mass and first year survival to investigate the role
maternal age plays in successful reproduction. Long-term uninterrupted life history
data available for Marion Island’s southern elephant seals and mass change
estimates from photogrammetry data allow for assessment of age related
reproduction performance and trade-offs. Known-aged adult females were
photographed for photogrammetric mass estimation (n=29) and their pups weighed
at weaning during the 2009 breeding season. Maternal age and proportional mass
loss positively influenced pup weaning mass. In turn first year pup return rates (as a
proxy for survival) were assessed through the intensive mark-recapture program.
Pup survival increased with female age and weaning mass. Pups of young females
aged 3 to 6 years have a lower 1st year survival probability compared to pups of older
and larger females.
