Summary
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.
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Costa, D.P., Trillmich, F. & Croxall, J.P. Intraspecific allometry of neonatal size in the antarctic fur seal (Arctocephalus galapagoensis). Behav Ecol Sociobiol 22, 361–364 (1988). https://doi.org/10.1007/BF00295105
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DOI: https://doi.org/10.1007/BF00295105