Canadian scientists have observed a case of learning and culture in a killer whale. A four-year-old orca in a marine park in Ontario has found a way not just to provide fresh fowl for supper, he has shown other young whales how to do the same thing.

The precocious predator made a practice of regurgitating his fish supper and then lurking just below the water's surface. The moment a gullible gull touched down for a free meal, the creature lunged.

According to New Scientist today, within a few months the whale's younger half-brother began trying the same trick. Then a six-month-old calf and an older male at Marineland in Niagara Falls started doing the same thing.

"They are in a way setting a trap," animal behaviourist Michael Noonan of Canisius College in Buffalo, New York, told the magazine. "They catch three or four gulls this way some days."

The capacity to innovate and then transmit the innovative technique - in a word, culture - was once supposed to be one of the things that separated humans from other mammals. The others were language and tool use.

But biologists observed that animals could communicate, and that great apes had a capacity to understand and even use human language. Then other biologists began observing sophisticated tool use, not just in primates but in sea otters and birds such as crows.

A British team has also recorded a range of cultural traditions within chimpanzee groups. Today's report suggests killer whales, too, can learn and pass on their learning.

"I'm not surprised," said Phil Hammond of St Andrews University, in Scotland. "It is the sort of thing killer whales ... are known for doing: coming up with inventive ways of catching their prey."