'Extreme polygamy' may be pushing male elephant seals to an early grave

Embargoed until: Publicly released: 2023-03-22 11:01

Australia; TAS

user:CillanXC, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

Male southern elephant seals are more likely to die at a young age than female elephant seals and it could be that their 'extreme polygamy' is to blame, according to Australian scientists. The researchers monitored a colony of elephant seals on Macquarie Island and found that male elephant seal survival was around 5–10% lower than females of the same age until they reached about 8 years old, when the male survival took a turn for the worse and dropped to about 50% compared to around 80% for females. Male southern elephant seals can grow to reach nearly five times the weight of females and dominant males have large harems of females. The authors say that while their size difference might play a role - the timing of the drop in male survival suggests it might have more to do with their extreme polygamy.

Media release

From: The Royal Society

Extreme polygyny results in intersex differences in age-dependent survival of a highly dimorphic marine mammal

Royal Society Open Science

Southern elephant seals are highly polygamous marine mammals. The species is known for the extreme size difference between dominant males, who reach nearly four times the size of adult females. This study illustrated the differences between survival rates of male and female seals as they aged. Male survival rates were consistently lower until eight years of age. After that, male survival decreased rapidly while female survival remained constant. This difference may be due to the different energetic requirements of adults. Overall, this research highlights how sex-specific survival rates in southern elephant seals are shaped by ecological interactions and evolutionary specialisation.

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Journal/
conference: Royal Society Open Science

Research:Paper

Organisation/s: University of Tasmania, Australian Antarctic Division

Funder: S.V. was funded through a Tasmania Graduate Research Scholarship.

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