Model helicopters have been deployed to sniff the breath of shy whales as the animals rise to the surface of the oceans.

Samples of breath captured by the remote-controlled helicopters are helping researchers to determine the health of whales in the wild.

The helicopters were fitted with sterilised Petri dishes before being flown into the air exhaled by whales through their blowholes as they surface.

Germs contained in the cloud of gases, water and mucus exhaled by the whales after holding their breath for up to 40 minutes are helping researchers to find out what diseases they carry.

Until Karina Acevedo-Whitehouse, of the Zoological Society of London, came up with the idea of using remote-controlled aircraft, it had been impossible to get samples from whales in their natural habitat.

She said that some creatures, notably grey whales, would swim close enough to research vessels so that she could lean out with a long pole fitted with Petri dishes to obtain samples. Others, especially blue whales, were usually reluctant to get too close to boats.

The smell of whale breath, she said, usually had an aroma of the sea. “It varies quite a lot,” she said. “It’s a very, very marine-type, not surprisingly. It smells like the ocean. But sometimes it’s pretty rotten. We’ve been pretty worried when the wind changes and you get completely drenched in it – they didn’t smell well.”

Sampling has been carried out on blue and sperm whales, both of which usually remain some distance from the researchers, and on pilot whales, grey whales and bottle-nosed dolphins.

Some testing took place off Gibraltar but mainly it was done in the Gulf of California off the Mexican coast.

Once individual whales or pods have been found, it is often possible to predict where they will next surface and when, allowing researchers to get a helicopter in position ready to dive through a whale spout.

The spouts tend to be longest in sperm whales, which can hold their breath for 40 minutes or more; blue whales exhale in several short bursts, each little more than a second long.

Mini-helicopters were chosen in preference to remote-controlled aircraft because they can hover over a position where a whale is expected to surface and are more manoeuvrable.

Laboratory analysis of the pathogens is still taking place and the results are expected early next year. Dr Acevedo-Whitehouse said: “We have extremely limited knowledge of the health of our wild, free-ranging whales. Our new technique gives us the opportunity to gain a fascinating and valuable insight into the pathogens affecting these extraordinary creatures.”

She added: “Scientists have always found it difficult to study diseases in whales because of their size. Most of the studies on whale pathogens have focused on dead, stranded or captive animals, which are hardly representative of the normal population.”

The research was carried out for the Zoological Society of London in collaboration with the Centro Interdisciplinario de Ciencias Marinas (Cicimar), part of the National Polytechnic University of Mexico.

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