Polyamorous male seals are dying earlier than they would normally as they try and keep up with a harem of around 100 females, research shows.
A study of 14,000 southern elephant seals at Macquarie Island in the south-western Pacific, found that although survival rates for males and females are roughly comparable for juveniles, male survival rapidly decreased after eight years of age.
Their survival rate dropped to around 50%, while female survival remained constant at 80%.
Adult males can weigh up to almost five times that of adult females, the study which was published in the Royal Society Open Science journal, shows.
Study author Sophia Volzke from the University of Tasmania said the largest and fattest male seals had a reproductive advantage.
“They can only get food from the ocean. When they come on land [to breed] they’re competing with other males for access to females.
“They need to have fat resources stored to be able to fight other males and survive on land without eating anything for weeks or months at a time.”
She added that the species exhibits “extreme polygyny” in which a small proportion of the largest and most dominant males – known as beachmasters – control harems of breeding females.
“One huge beachmaster can have a harem of up to 100 females,” she said.
“Once the harems get that big they might allow for a younger male to be an assistant beachmaster.
“It depends on how big the harem is and the geography of the beach – if you have a really long beach, you’re more likely to have a bunch of small harems."
The researchers believe males try to gain weight as quickly as possible in order to compete and this results in lower survival rates.
