From the Antarctic: Brutal, selfish lives of seals hook zoologist

By SIMON COLLINS at Scott Base

Scientists studying Antarctic seals have found a violently competitive society where the males mutilate each other's genitals and half the pups die before they are a year old.

The Weddell seals are one of the most individualistic species on Earth, says Canadian-born zoologist Kathryn Wheatley.

She and two assistants catch the seals with a bag and lift them into a chain block to weigh and tag them and take blood samples.

Unlike almost every other species, mothers who are still breast-feeding do not even react when their pups are picked up to be weighed.

"They don't care about each other at all. They warn each other away from their space," Ms Wheatley says.

"The mothers do sacrifice a lot for their pups, storing up fat before giving birth and then fasting for about two months so they can stay with their pups constantly while they are breast-feeding.

"Mum loses a third of her weight, typically 4 to 4.5kg a day. The pup gains 2 to 2.5kg," Ms Wheatley says.

But some first-time mothers abandon their pups before they are weaned.

Ms Wheatley describes the sad sight of abandoned pups going from seal to seal on the frozen sea ice where they breed, looking for their mothers. Eventually they die.

"The mothers get better with practice. But when they stop breast-feeding, even the best mums often just dive under the ice and swim away.

"You often see the pups stay around for about a week till they realise mum's not coming back," Ms Wheatley says.

"A lot don't even teach their pups how to dive and forage. It is literally sink or swim."

As she describes it, the males are worse. Trails of blood leading from almost every hole in the McMurdo Sound seal colony she is studying are the marks of wounded male seals.

A single dominant male takes over at each colony by attacking any other male who ventures into the territory, mauling especially their tails and their penises to knock them out of contention for the females.

The losers crawl, bloodied and mutilated, to the surface.

Ironically the dominant male, after getting the colony's females pregnant, has to stand guard underneath his air hole to fight off other males throughout the breast-feeding season. With no time to feed himself, he quickly loses weight and usually dies within a year.

Ms Wheatley's careful studies show that pups also usually die within a year unless their mothers have stored enough fat to pass on to them.

"That one probably won't survive," she says, pointing to a small pup. Its mother weighs a mere 280kg.

Early death also awaited a snow-coated pup crying for its mother, who had so little spare fat that she had gone off to catch more fish in the middle of the breast-feeding months.

Ms Wheatley says the mothers seem to need to weigh 400 to 450kg when they give birth for pups to survive. Some weigh up to 600kg.

From examining their excrement, she has learned the seals eat mainly a deep-water Antarctic silverfish called Pleuragramma, diving for up to an hour and swimming up to 7km underwater on a single breath.

They dive as much as 700m down, avoiding the bends by breathing out just before they plunge so that there is no air in their lungs. They store large amounts of oxygen in their body tissues instead, taking advantage of their bulk.

Ms Wheatley clearly cares for the seals, calling them "my girls" and walking a few hundred metres from the shipping container she lives in to check on all 62 breeding mothers in the colony every day.

She did not choose to study seals, but studied at a university in Canada where researchers were trying to find a contraceptive injection to halt a seal population explosion.

She got a job helping with the research, and was hooked. The contraceptive, incidentally, was never used.

Ms Wheatley moved her seal studies to Macquarie Island, southwest of Stewart Island, and then to Antarctica as part of a doctoral project for the University of Tasmania.

She is philosophical about her seals' rather nasty and short lives.

"The 50 per cent death rate keeps them at a steady population," she says.

And the first-time mums who abandon their pups do it because they simply do not have enough blubber to keep the pups alive.

"They take a long-term view," Ms Wheatley says. "They cut their losses this year so that they can build up their own condition and have pups successfully in the future."