Intraspecific allometry of neonatal size in the antarctic fur seal (Arctocephalus galapagoensis) |
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Authors: | D P Costa F Trillmich J P Croxall |
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Institution: | (1) Long Marine Laboratory, Institute of Marine Sciences, University of California, 95064 Santa Cruz, CA, USA;(2) Abteilung Wickler, Max-Planck Institut für Verhaltensphysiologie, D-8131 Seewiesen, Federal Republic of Germany;(3) British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, CB3 OET Cambridge, United Kingdom |
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Abstract: | 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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