Getting the gull: baiting trick spreads among killer whales.
The innovative killer whale lives in MarineLand, an attraction in Niagara Falls, Canada, and behavioral biologist Michael Noonan happened to videotape the orca's early ambushes. As Noonan kept track, other orcas in the park also started baiting gulls this way.
The spread of this trick might be an orca version of people learning from each other, proposes Noonan, a researcher at Canisius College in Buffalo, N.Y. His records offer a rare look at the path of a tradition, he reported last week in Snowbird, Utah, at the annual meeting of the Animal Behavior Society.
"There's nothing else so well documented in cetaceans," says Bennett G. Galef Jr., a social-learning specialist at McMaster University in Hamilton, Ontario. He finds the new orca behavior "plausible" as an example of cultural learning but notes that it hasn't been confirmed by experiments.
Earlier studies of marine mammals, as well as primates, birds, and a few other animals, have suggested that animals sometimes pass along newly developed behaviors. Young orcas seem to learn ways of hunting, vocal quirks specific to their pod, and, perhaps, aspects of baby care. Observing the spread of a tradition has been difficult in the wild.
Noonan set up his orca watch at MarineLand more than 8 years ago to study the orcas' calls. By lucky accident, he says, he was there for the start of the gull baiting. Gulls lurked around the park, ready to snatch fish at feeding time, and occasionally an orca snapped up a careless bird for a meal or entertainment. However, Noonan says that for the first 4 years of his observations, he saw no systematic baiting of gulls by orcas.
Then, Noonan's camera array captured images of a young male leaping out of the water and spitting partially eaten fish onto the surface. The orca dropped back but stayed within striking distance of the mess. When a gull swooped down for a snack, the orca lunged.
For the 3 months after Noonan first observed the trick, only this young male baited gulls. Then, the cameras picked up his younger half brother spitting fish and ambushing birds. Later, two adult females started the activity.
The pattern of youngsters and females being the first to adopt a fashion fits other records of cultural transmission. "I hate to stereotype, but your granddad is the stodgiest one in the family," says Noonan.
Recently, he notes, one of the adult males has started what may be a variant of the strategy. That orca picks up fish from the pool's drain and spits them undigested onto the water's surface.
James Ha of the University of Washington in Seattle studies orcas in the wild. He says that he has seen the killer whales catching and playing with gulls. Now, he plans to look for gull baiting.
The baiting behavior has been a mixed blessing for the park, says Noonan. It's scientifically exciting, but visitors don't always react well to orcas dangling gulls from their months.
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|Date:||Aug 20, 2005|
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