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Smart seal. Harbor seals learn to distinguish the calls of fish-eating whales from those of seal-eaters (spectrogram, inset).

Sound-Savvy Seals

Up there with sex and eating, recognizing predators is a top priority for any prey species. But because experience with hunters is often fatal, scientists thought it unlikely that animals would pick up the ability to recognize a predator. Now a group has found evidence that harbor seals learn to tell which killer whales are dangerous by eavesdropping on their conversations.

Animal behaviorist Volker Deecke of the University of St. Andrews in Fife, U.K., and his colleagues at the Vancouver Aquarium Marine Science Centre noticed that harbor seals seem to flee from the underwater calls of transient groups of whales that prey on seals and dolphins, whereas they ignore the calls of the familiar local resident killer whales, which feed exclusively on fish.

The researchers tested the observation by playing recorded calls of both groups at popular harbor seal hangouts in British Columbia to see how the seals would react. The calls of the mammal-eating whales caused almost half of the seals to bolt immediately, whereas the calls of the local fish-eating whales had almost no effect. When Deecke played the calls of harmless whales from Alaska, the seals again reacted strongly. Because they couldn't have learned to associate these unfamiliar calls with danger, Deecke thinks the seals slowly learn that the local whales are benign. This saves the seals from wasting energy evading harmless whales. The results, reported in the 14 November issue of Nature, could also help explain why transient killer whales vocalize so much less than residents do, Deecke says.

"It's suggestive to me that seals are pretty savvy," says marine biologist Ron Schusterman of the University of California, Santa Cruz. He suspects that the seals aren't just getting used to the friendly whales but might also be learning to associate the transient whales with danger: "I think there is something more complicated going on." A true test would be to see if younger seals that haven't had as much experience still react more to the safe whales, he says.

Related sites
Vancouver Aquarium Marine Science Centre
Killer whale vocalization