Study finds males, who can command a harem of up to 100 females, driven to gain weight as quickly as possible by foraging in areas full of  predators

Sex on the beach: pressures of extreme polygamy may be driving southern elephant seals to early death

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2023-03-22 13:30:03

Study finds males, who can command a harem of up to 100 females, driven to gain weight as quickly as possible by foraging in areas full of predators

A study of 14,000 southern elephant seals (Mirounga leonina) at Macquarie Island in the south-western Pacific, has found that while survival rates for males and females are roughly comparable for juveniles, male survival rapidly decreased after eight years of age, dropping to around a 50% survival rate, while female survival remained constant at 80%.

Southern elephant seals differ significantly in size: adult males can weigh up to nearly five times that of adult females. The size differences typically begin to emerge between three and six years of age, when the animals undergo maturation.

Sophia Volzke, the study’s first author and a PhD candidate at the University of Tasmania, said the largest and fattest male seals had a reproductive advantage.

“They can only get food from the ocean,” she said. “When they come on land [to breed] they’re competing with other males for access to females.

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