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Last Updated: Wednesday, 6 April, 2005, 10:54 GMT 11:54 UK
Butterflies 'follow flightpaths'
Small tortoiseshell butterfly, Royal Society
Butterflies such as this small tortoiseshell were fitted with tiny radar transponders
Butterflies do not flutter aimlessly around the garden but instead follow precise flightpaths, scientists say.

A UK team of researchers made the discovery by tracking the insects with radar, using tiny transponders attached to the backs of butterflies.

This gave them information on the insects' flightpaths, speeds and foraging behaviour - some of which could guide conservation measures.

Details of the research appear in Proceedings of the Royal Society B.

If we can get the funding, we'd like to do a much bigger study on butterflies over several years
Juliet Osborne, Rothamsted Research
"We've never been able to see their flight tracks up to 1km before and it's showing us that they do seem to be quite directive in the way they're flying," said co-author Lizzie Cant of Rothamsted Research in Harpenden, UK.

The scientists tagged peacock (Inachis io) and small tortoiseshell (Aglais urticae) butterflies with transponders weighing just 12mg.

After checking that the devices did not affect their behaviour, the researchers released 33 insects into a large field being scanned by radar on the Rothamsted estate.

The flightpaths of individual butterflies were then tracked, some of them flying up to 1km from their release point. The researchers successfully recorded the movements of 30 of the insects they released.

Gone loopy

The results revealed these butterflies had two distinct types of flight pattern: fast, straight movement and slower, non-linear movement.

During straight flight, the butterflies zipped along at about 2.9m/s. During the slower type of flight, the insects foraged for nectar from flowers and flew in loops, with a speed averaging 1.6m/s.

Flying in loops seems to perform an orientation function, helping the insects identify flowers or hibernation spots.

The butterflies were able to identify and avoid unsuitable habitats such as dense trees from up to 200m away. They seem able to identify suitable foraging habitats from about 100m away.

"Finding out how butterflies choose where to go and how they use and feed in the landscape is going to prove very useful to conservationists," Dr Juliet Osborne, of Rothamsted, told the BBC News website.

"If we can get the funding, we'd like to do a much bigger study on butterflies over several years. This would give us information on how different species fly and how they're affected by different landscapes.

"If you're talking to farmers about whether they should have hedges and what kinds of crops they should have to increase biodiversity, the more we know about the different species, the better."

Lizzie Cant plans to repeat the experiment on rarer species such as the high brown fritillary (Argynnis adippe) and marsh fritillary (Euphydryas aurinia).

Radar tracking has previously been used to trace the movements of bumblebees and honeybees.

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