It's a technique more commonly used to track big game in the wild. But yesterday scientists undertook the intricate task of attaching gossamer thin tags to delicate butterflies.

It's a technique more commonly used to track big game in the wild.

But yesterday scientists undertook the intricate task of attaching gossamer thin tags to delicate butterflies.

Experts from Helsinki University joined forces with the Norfolk Wildlife Trust to carry out a series of tests using specially imported Glanville Fritillary butterflies.

Carried out at East Wretham Heath, near Thetford, the tests were designed to improve the university's knowledge of the species and provide an insight into declining numbers.

Daryl Stevens, the trust's field officers for the Brecks, said: "The butterflies were imported from Finland and had tiny copper wires attached along their bodies using a special glue.

"Obviously the butterflies are very fragile so it was a time consuming operation.

"They were then released and radar equipment was used to track their movement and how they distribute.

"The scientists will now go away and study the results and hopefully develop a better understanding which will allow them to improve the species' survival."

The heath, which is popular with bird spotters and walkers, was selected because the radar equipment required a flat environment to track the tiny insects.

Glanville Fritillarys - recognisable by its orange, black and white "checkerspot" pattern - generally occupy grassland and coastal landslips and are found throughout Europe but are now rare in the UK.

Numbers have declined in recent years because of coastal protection measures. There are only a handful of core breeding areas and it is regarded as a vulnerable species. It spends most of its life as a black, spiny caterpillar.

UK records suggest a distribution which once went as far north as Lincolnshire. However, by the middle of the 19th century the Glanville Fritillary was known only from the Isle of Wight and the coast of Kent between Folkestone and Sandwich. It became extinct in Kent by the mid 1860s.