Intraspecific allometry of neonatal size in the Antarctic fur sea (Arctocephalus galapagoensis)

• Published in: Behavioral Ecology and Sociobiology
• Main Authors: Costa, D.P., Trillmich, F., Croxall, J.P.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Springer 1988
• Subjects: Antarctic; The Antarctic; Antarc*; Antarctic Fur Seals; Arctocephalus gazella; Polar Biology
• Online Access: http://nora.nerc.ac.uk/id/eprint/521544/; https://link.springer.com/article/10.1007%2FBF00295105

Intraspecific allometry of pup mass as a function of maternal mass was analysed in Antarctic fur seals (Arctocephalus gazella), a highly dimorphic species. The allometric exponent was 0.6, much lower than in interspecific comparisons. Slopes were the same for mother-son pairs as for mother-daughter pairs, but adjusted means were significantly higher for the former, indicating higher reproductive effort of mothers of sons. The correlation of maternal mass with pup mass explained 59% of the variance in female pup mas but only 18% of that in male pup mass. Females appeared to produce sons which were as big as possible. Relative pup mass decreased with increasing maternal mass indicating a lower reproductive effort of bigger and presumably older mothers, contrary to expectations from life history theory. Sex ratio of pups showed no relation to maternal mass.