Killer whales and chimpanzees both pass on "traditions" to other members of their group, according to two separate studies of feeding behaviour. The findings add to evidence that cultural learning is widespread among animals.
One study involved killerwhales at Marineland in Niagara Falls in Ontario, Canada. An inventive male devised a brand new way to catch birds, and passed the strategy on to his tank-mates. The 4-year-old orca lures gulls into his tank by spitting regurgitated fish onto the water's surface. He waits below for a gull to grab the fish, then lunges at it with open jaws. "They are in a way setting a trap," says animal behaviourist Michael Noonan of Canisius College in Buffalo, New York, who made the discovery, "They catch three or four gulls this way some days."
Noonan had never seen the behaviour before, despite three years of observations for separate experiments. But a few months after the enterprising male started doing it, Noonan spied the whale's younger half-brother doing the same thing. Soon the brothers' mothers were enjoying feathered snacks, as were a 6-month-old calf and an older male. Noonan presented the research this month at the US Animal Behavior Society meeting in Snowbird, Utah.
Wild dolphins off the west coast of Australia were the first marine mammals in which cultural learning was observed. They apparently learn from group-mates how to use sponges to protect their snouts while scavenging (New Scientist, 11 June, p 12). But the evidence from killer whales is much more conclusive because the process was observed from start to finish.
Some researchers have suggested that many purported examples of cultural transmission can instead be explained by individuals discovering the skill on their own rather than following another's lead. But because the gull-baiting behaviour is so unusual, "it would be hard to argue that it is individual learning", says ethologist Janet Mann of Georgetown University in Washington DC, one of the authors of the dolphin sponging study. Behavioural scientist Andrew Whiten of the University of St Andrews in the UK agrees, "This is a particularly clear set of observations."
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