Butterflies know where they are going, scientists reveal

Butterflies make their way to flowers deliberately, researchers say. File picture / BOP Times

Their movements around the garden seem no more than delicate, random meanderings but butterflies can spot promising areas for nectar from up to 200m away and can purposely avoid places unattractive to them, scientists revealed yesterday.

Using radar tracking devices which are attached to the insect's back, scientists at the Rothamsted Research Institute in Harpenden, Hertfordshire, are the first to plot the exact path of butterfly flight.

Transponders, 16mm pieces of wire weighing just 12 milligrams (less than 5per cent of the insect's weight) were attached to 30 peacock and tortoiseshell butterflies, enabling their movements to be plotted accurately, via a radar dish, from up to 1km away.

Previously, the only way scientists had been able to monitor butterflies was by the naked eye - impossible from more than 100 metres - or by marking and collecting butterflies, a technique that only tells researchers if a butterfly is in an area and not why or how it got there.

But by use of the transponders, a radar tracking team relayed specific location details to field researchers who found themselves able to keep up with the butterflies as they fluttered through a field.

The insects were found to be undertaking fast, directed flights to potential feeding sites while between foraging missions, they undertook looping "orientation" flights.

"Though this does not establish what is going on in their brains, it does show how butterflies can see a potential area of forage and decide if it looks familiar or suitable," said researcher Lizzie Cant.

"They are intent on reaching forage and not just blown in by the wind."

When it comes to landscapes that are less desirable, a butterfly can evidently be just as decisive.

On one occasion, a number of the butterflies under examination were heading towards a tree line in the middle of a field. They wheeled away, en masse, to avoid it.

The harmonic radar technology used to track the butterflies was developed to observe the Tsetse fly in Africa, then used by Rothamsted scientists to observe bee flight in the UK.

Its application to monitor the flight patterns of a butterfly is compared by Rothamsted to watching the moving 'blips' on a ships radar screen.

Attaching the transponder is a delicate process, involving the removal of fine 'hairs' on the creature's back, applying a thin layer of paint onto which the transponder - mounted on a sticky pad - can be applied.

The findings contribute to a growing body of research that shows the movement of insects and birds to be more sophisticated than had been thought.

One of the birds whose flight has been recently analysed is the pigeon. Traditionally, its homing ability has been thought to rely on a map and compass mechanism that involves an internal clock and a compass direction related to the sun.

But recent work has shown that this is not enough, and that the creatures must also have a large-scale 'mental map' which gives them information about their current position in relation to the loft they return to.

Ms Cant said the research would enable conservationists to protect and conserve butterflies which, along with bees, are important pollinators of wild flowers.

"Butterflies provide a crucial service to plants in many ecosystems," said Ms Cant.

"This research will help us to understand a little more about how they survive in a countryside that is becoming more and more fragmented. The ideal application of this work would be to now use it with less common and endangered species."

- INDEPENDENT