Why male elephant seals are being worn out by sex

By Mark Waghorn via SWNS

Male elephant seals are being worn out by sex, according to new research.

They defend harems during the breeding season, while forgoing food and the duties that come with serving up to 50 females are costly.

They die younger than less randy peers - although it is worth it for them genetically, say scientists.

The marine mammals have to guard partners and their pups - as well as the beach they live on from rivals.

They can also incur injuries during fights with other males.

And because they stay on land during the breeding season, the five ton creatures don't eat for three months while expending energy patrolling and mating with all the females in their group.

Lead author Dr. Kyle Lloyd, of Pretoria University in South Africa, said: "These breeding seasons are quite chaotic.

"There's lots happening - the beaches are so busy and the males are working hard."

He spotted males with the most females were losing weight and body condition over the breeding season in Marion Island in the Indian Ocean.

His team examined 34 years' worth of records for the population based on annual tagging and counting campaigns - including the life histories of 324 breeding males.

They found dominant males usually survive to an age of eight to ten years - and died younger when their harems were bigger.

This was particularly true for males that had their first harem at a younger age - starting at about five years old.

By contrast, females generally live at least 20 years, reports New Scientist.

If the males had large harems year after year they might father up to 200 pups.

But the study in Animal Behaviour found their chance of survival got lower each year.

Lloyd said: "That cost just got worse and worse. But in evolutionary terms that cost is worth it.

"The males have already passed on their genetic material."

Southern elephant seals live in sub-Antarctic and Antarctic waters that feature brutally cold conditions but are rich in the fish and squid they feed on.

They breed on land - and get their name from the trunk-like nose males develop as they become sexually mature.

Fights between dominant males and challengers can be long, bloody, and extremely violent, with the loser often suffering serious injury.

Southern elephant seals are open ocean predators and spend much of their time at sea. They only come to shore to reproduce and to molt their fur. The rest of the year is spent feeding at sea.

They have few predators but killer whales, leopard seals, and some large sharks are known to feed on them.

Historically, southern elephant seals were hunted to very low numbers because of the value and volume of their blubber, which was rendered into oil.

Commercial hunting ceased in 1964 because numbers were too low to be worth the long trip to the Southern Ocean.

Since that time, populations have rebounded and the southern elephant seal is considered a species of least concern.