University Of Tasmania
155982 - Extreme polygyny results in intersex differences.pdf (538.46 kB)
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Extreme polygyny results in intersex differences in age-dependent survival of a highly dimorphic marine mammal

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Developmental differences in vital rates are especially profound in polygamous mating systems. Southern elephant seals (Mirounga leonina) are highly dimorphic and extremely polygynous marine mammals. A demographic model, supported by long-term capture–mark–recapture records, investigated the influence of sex and age on survival in this species. The study revealed clear differences between female and male age-dependent survival rates. Overall juvenile survival estimates were stable around 80–85% for both sexes. However, male survival estimates were 5–10% lower than females in the same age classes until 8 years of age. At this point, male survival decreased rapidly to 50% ± 10% while female estimates remained constant at 80% ± 5%. Different energetic requirements could underpin intersex differences in adult survival. However, the species' strong sexual dimorphism diverges during early juvenile development when sex-specific survival rates were less distinct. Maximizing growth is especially advantageous for males, with size being a major determinant of breeding probability. Maturing males may employ a high-risk high-reward foraging strategy to compensate for extensive sexual selection pressures and sex-specific energetic needs. Our findings suggest sex-specific adult survival is a result of in situ ecological interactions and evolutionary specialization associated with being a highly polygynous marine predator.


Publication title

Royal Society Open Science



Article number









Institute for Marine and Antarctic Studies


The Royal Society Publishing

Place of publication

United Kingdom

Rights statement

© 2023 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License, which permits unrestricted use, provided the original author and source are credited.

Repository Status

  • Open

Socio-economic Objectives

Biodiversity in Antarctic and Southern Ocean environments