Scientists discover 'most important' blue whale colony

"What we are seeing is one of the biggest feeding and breeding sources, at least in the southern hemisphere," Ernesto Escobar, a spokesman for the Ballena Azul (Blue Whale) project, said. The project has been studying the animals in Chile for the past four years.

The research team has just returned from three months studying the whales in the Gulf of Corcovado, off the remote island of Chiloe in Chile's south, in association with the BBC, which will be showing the trip on its Planet Earth programme.

On the trip, 65 blue whales and 51 humpback whales were sighted "which confirms the existence of one of the most important whale habitats in Chile and the planet", Ballena Azul said in a statement.

"The population of blue whales in Corcovado shows us that a large number do not migrate to Antarctica," Mr Escobar said.

Blue whales are the biggest animals ever to have lived but were hunted to the brink of extinction during the first half of the 20th century until a ban in 1965. Whaling was especially savage in the southern hemisphere, where the International Whaling Commission estimates only 400 to 1,400 remain.

Despite finding of the Corcovado colony, the scientists also found a new peril. The waters off Chile are busy with fishing and tourist ships and rubbish from these, such as plastic bags, polystyrene, ropes and fuel, can be found in the same waters as the whale's food sources, meaning they could accidentally swallow them and die.

Conservation groups have been pressing the Chilean government to declare the area a protected zone, something Mr Escobar said was "now even more important".

Dr Bruce Mate, the director of the marine mammal programme at Oregon State University, who has developed satellite monitoring and radio tagging technology to track whales, has also been involved in the Ballena Azul project.

He said he and project leader, Dr Rodrigo Hucke-Gaete, expected to publish the findings of a tagging experiment in the next few months. The team tracked five whales for up to 203 days and found the longest single journey by one whale was 9,400km (5,840 miles). The five tagged whales together covered a distance of 26,000km, moving north to the Nazca ridge, some 25 degrees south of Ecuador.

Dr Mate said they had not tracked what happened when the animals moved south to see if they went as far as Antarctica.

But even so, he said he did not believe these Chilean whales were part of the Antarctic whale population, making it premature to talk of a change in migration patterns. "They probably don't go to the same places and speak in different local dialects," he said.

Dr Mate said they were also distinct from northern hemisphere whales, which migrate between the west coast of the US to around 8 degrees north of Ecuador.

Dr Mate said further study is needed to discover more of the blue whale's secrets, and protect them in future.

"It would be outrageously arrogant to allow them to disappear out of neglect," he said.