4 March 2011
Orcas are usually highly communicative killer whales, but researchers from St Andrews University have found out that they hunt in complete silence to avoid being overheard by their prey.
Click to hear the report:
Killer whales whistle to talk to each other and click to find their way around. It's the echoes from these clicks that help the animals to map their surroundings and to pinpoint the location of their next meal.
But while one type of killer whale eats fish, the other hunts marine mammals, including seals and porpoises. A shoal of salmon can't hear the clicking of an approaching killer whale, but the mammals, with their highly sensitive underwater hearing, can.
The researchers used underwater microphones to listen to killer whales hunting seals off the coast of Alaska. They found that the animals fell completely silent when they were hunting. But, somehow, they still managed to organise themselves into groups - often spreading out up to a mile apart, before coming back together and calling loudly to each other while they shared their catch.
The scientists now hope to attach satellite trackers to individual killer whales, to find out more about this stealthy behaviour.
Victoria Gill, BBC News
Click to hear the vocabulary:
make a loud, high sound
sounds which can be heard to repeat after the original noise has stopped
the area around a person or animal
- to pinpoint
to search and find
certain types of warm-blooded animals (e.g. humans, dogs)
large group of fish, swimming together
- fell silent
became completely quiet
- spreading out
separating to cover a wider area
food caught while hunting
moving about in a careful way, trying not to be seen