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Last Updated: Thursday September 24 2009 07:04 GMT

Blue whales 'now sing louder'

A blue whale

Blue whales are being forced to sing louder to be heard over man-made noises like ships engines, scientists say.

The endangered mammal uses sonar, or sound waves, to find its way, find food, avoid predators and communicate.

But recently the increase ships using things like high-tech sonar and loud propellers has made it harder for whales to be heard.

Scientists reckon it could also be causing whales to become confused and beach themselves.

Blue whale tail

The research, which was done by the University of Zurich, recorded sounds of the blue whales 'talking' underwater off the coast of Canada over 11 days in 2004.

The recordings show the whales had to 'chatter' more often and for longer to communicate with each other, find food and find a mate.