Gulls' vicious attacks on whales

Whales off the coast of Argentina have acquired a new enemy – seagulls. The gulls have learned to feed on the whales by landing on their backs and just pecking away the skin and blubber – something never seen in any other part of the world.

The attacks around Peninsula Valdes were first noted about 35 years ago but systematic studies have only recently begun. The proportion of whales attacked annually has soared from 1% in 1974 to 78% today.

Sores on a whale's back (Mariano Sironi)

The gulls peck centimetres into the whales’ blubber. “You see big open sores, which we thought were pock marks of infection,” recalls Roger Payne from the Ocean Alliance. “Some are half a metre across and the edges look like thousands of bites."

Whale mother and calf from above (Mariano Sironi)

The gulls have learned to attack mothers and calves more often than other whales. In the last survey, 80% of attacks were on mother-calf pairs in what is an important breeding ground – one of few remaining – for the endangered southern right whale.

Marks on a whale's back (Mariano Sironi)

Recent years have seen a big increase in the number of dead whales, particularly calves. “The mothers spend less time nursing, and we’re seeing thinner calves,” says Roxana Schteinbarg, director of the Instituto de Conservacion de Ballenas.

Researchers speculate that the kelp gull population increased decades ago with the development of fish processing in the area. Waste from processing plants may have attracted gulls into the area, which then learned to get more food from whales.

The whales can spend a third of their time in evasive manoeuvres. “They had their last meal several months ago and won’t feed for several more months so they should be conserving their energy,” says Roger Payne, “but the gulls drive them crazy.”

“For years we thought shooting [the gulls] was impossible but maybe it’s something we have to do,” says Roxana Schteinbarg. Scientists fear the whales may go elsewhere – to their detriment, perhaps – if the problem can’t be solved.