Large Blue butterfly officially saved – How did they do it?

Saving the Large Blue butterfly practices will aid rescue missions of other endangered insects, researchers say in the journal Science

June 2009. On the 25th anniversary of the large blue butterfly reintroduction to Britain, ecologists are, for the first time, publishing details of the decades of research that helped them rescue this rare butterfly.

Sir David Attenborough said: "The restoration of the Large Blue butterfly to Britain is a remarkable success story, illustrating the power of ecological research to reverse damaging environmental changes. It is, moreover, a tribute to the dedication of many practical conservationists who have skillfully recreated its specialised habitat in our countryside."

The research, by Professor Jeremy Thomas from the University of Oxford and the Natural Environment Research Council's Centre for Ecology & Hydrology with his colleagues, will be published online by Science at the Science Express website on 18 July 2009.

Success story

The large blue is now one of just three UK butterflies on course to meet the Convention of Biological Diversity's target to reverse species' declines by 2010. This rebound has closely followed the predictions generated by the model published today in Science. Professor Thomas explained: "There are few known examples of a model being able to predict the success of a conservation effort as well as ours did, for any insect. We are confident that this detailed information will help those attempting to bring other endangered species back from the brink."

Dependent on 1 ant species

The study shows how the large blue's extreme dependence on a single ant species led to the butterfly's demise - their habitat became overgrown, causing soil temperatures to drop and the ants to diminish. Before this discovery, butterfly collectors were generally blamed for the decline of this butterfly, also known as Maculinea arion.

Global flagships for butterfly conservation

In the 1970s, the International Union for Conservation of Nature selected three butterflies, including the large blue, as global flagships for the cause of lepidopteran conservation. These insects and others had been mysteriously disappearing for decades, despite attempts to save them.

While ecologists generally knew that the large blue had a complex life cycle, the butterfly's intense dependence on Myrmica sabuleti red ants only came to light once Thomas began studying Britain's last surviving large blue butterfly colonies.

Professor Thomas said: "For six years from May to late September I lived with the last UK colonies, measuring everything, including their behavior, how many eggs they laid, the survival of individual eggs, and how many caterpillars were in the plants. It was a bit like a detective story."

Thomas compiled this information into life tables, which show the number of new eggs and those that survived each year from 1972 to 1977 - which are now being published for the first time in the Science study.

Grass was too long

With these field data, Thomas and his coauthors explored the possible factors that could be causing the large blue's decline. They realised that the grass in the butterflies' habitat had grown too long, as farmers had gradually stopped grazing their livestock on these hillsides and a viral infection had killed many of the wild rabbits in the 1950s.

The soil on these overgrown grasslands was therefore too cool to support adequate numbers of M. sabuleti ants. Without enough ants to raise their young, the large blue butterflies dwindled. The researchers combined these ecological relationships into a numerical model, upon which future conservation efforts were based.

Grazing animals were the key

In the late 1970s, after 40 years of trying to save the large blue by fending off butterfly collectors, conservationists followed Thomas' recommendations and restored the butterfly's proper habitat by clearing scrub and reintroducing grazing animals in a project led by the Centre for Ecology & Hydrology (CEH).

From 1983, Thomas and co-author David Simcox from CEH began introducing large blue butterflies imported from Sweden into restored habitat sites. In 2008 the butterflies occupied 30% more colonies than they had in the 1950s, before the major decline began.

Restoring the large blue's habitat may also provide collateral benefits for other species that live there, the authors speculate in their study. On some of its conservation sites there have already been dramatic increases in rare birds, plants and other butterflies, such as the wood lark, pale heath violet and the pearl-bordered fritillary.

http://www.wildlifeextra.com/go/news/large-blue009.html