Sharks may be colour blind

A new study suggests sharks may be colour blind, challenging the long-held belief they were mainly attracted to yellow.

The joint study by researchers at the universities of Queensland and Western Australia says it is the contrast that is important, not the colour itself.

They say more studies need to be done but the advice is to avoid wearing brightly coloured costumes when swimming in the ocean.

Sharks were thought to be mainly attracted to yellow, based on tests carried out by the United States navy.

Australian researchers measured light-sensitive cells in the sharks' eyes to determine whether they could see colours.

"We looked at a number of different species and we found that in all cases they are probably colour blind," UWA associate professor Nathan Hart said.

"They have only a single type of cone photoreceptor in the eye, which is what we use for our sense of colour, but we have three - red, green and blue.

"They only have a single one, sensitive to green, so effectively they're colour blind. It is just like looking at a black-and-white TV."

Professor Hart says it is likely sharks are attracted to any bright colours.

"They were probably attracted to [yellow] because it would have had a very high contrast against the surrounding water," he said.

"That's why they [life jackets] are made yellow, so that people can spot people who are floating in the water."

Professor Hart says swimmers should wear "more muted colours or colours that match the background in the water better" but more tests are needed.

"Now we've actually worked out what the sharks can see, we can start thinking a little bit more deeply about this sort of question," he said.

The findings have been published in the international journal The Science Of Nature.
 

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