The killer whale, which, in spite of its name is in fact a species of dolphin, is one of the most intelligent animals on the planet. The researchers have now found new signs of its high mental capacities - the orcas' behavior is not purely instinctive, they manifest "cultural learning".

The discovery was made by Michael Noonan, an animal behavior professor at the Buffalo, N.Y., college, during a study at Marineland at Niagara Falls in Ontario, Canada. He observed how orcas are catching gulls by attracting them with bait fish. After spitting the dead fish onto the water's surface the mammal sinks waits for an unfortunate gull to take the bait.

This behavior is learned from older brother to younger brother, Noonan has found.

"It looked like one was watching while the other tried," Noonan said of the whale's initial behavior.

"It was once believed that most animal behavior, from the food they ate to the places they slept, was based on instinct. This new discovery supports the growing view that animals like killer whales are very prone to learning by imitation, and that they are 'cultural' by nature."