Savage sea lion feast shocks scientists

By ANNE BESTON environment reporter

New Zealand sea lions dine out on their pups, to the surprise of Department of Conservation scientists.

DoC marine biologist Dr Ian Wilkinson and his team discovered the cannibalism during a study of the Hooker's sea lions early this year.

The scientists were amazed to see 300kg males attacking pups on shore, dragging them into the sea and eating them.

As the female sea lions called for their pups, the males killed the young in the water, ripped them limb from limb and ate them.

"It's fair to say we were shocked," said Wellington-based Dr Wilkinson.

"The male would come ashore, grab the pup, swim 50 to 100 metres with it, shake it around, kill it, then bite off chunks and limbs and eat them.

"When it was happening, we would see whole groups of seabirds gathering nearby.

"Then all of a sudden, you would see a pup come flying out of the water and watch the carcass splash down. It's never pleasant to see that sort of thing.

"I don't think anybody enjoys seeing animals kill other animals."

Cannibalism has been seen among Canada's grey seals and elephant seals in Argentina, but has not been documented before among the Hooker's sea lion.

In the 12 weeks of study during the breeding season at Dundas Island, the scientists recorded 24 cases of cannibalism.

The team saw a female trying to defend her pup. The male sea lion attacked her and she had to swim away.

Male sea lions are up to three times the size of the females.

The cannibalism will be investigated further when the team returns to the animals' Auckland Island breeding grounds early next year.

Dr Wilkinson said it was too early to say if the behaviour of the male sea lions was "psychopathic" or renegade behaviour by a small group of males or whether it was more widespread.

He said male sea lions could be killing up to 2 per cent of pups each year, which was a concern as the Hooker's sea lion is officially classed as threatened.

They are confined almost entirely to two breeding grounds at the Auckland Islands, 200km south of New Zealand.

Numbers are estimated at between 13,000 and 17,000.

"It's not good for the species as a whole, but maybe it's clever feeding strategy for the individual males involved," Dr Wilkinson said.

"It's difficult to speculate on why they do it - maybe because the pups are an easy source of food.

"Normally the adult males might have to swim up to 400m out to sea and dive to catch squid."

In 1998, a mystery virus or bacteria wiped out more than half the pups born that year. It also killed 20 per cent of female sea lions.

Dr Wilkinson said the organism responsible had been isolated and was being studied, but had still not been identified.

Cannibalism had been recorded in at least 100 species of mammals, including humans, Dr Wilkinson said.