16 june 2009

Saving the Large Blue butterfly

Science | Environment

Large Blue butterfly
The extinct Large Blue butterfly was reintroduced into the UK in 1984

25 years ago the Large Blue butterfly was successfully reintroduced into the UK. To celebrate this landmark achievement an Oxford-led team has, for the first time, published the full story of how this was achieved in the journal Science.

The hope is that this information could help inform efforts to save other endangered insect species.

The Large Blue [Maculinea arion] became extinct in the UK in 1979 after decades of decline. However, before it became extinct Professor Jeremy Thomas, from Oxford University’s Department of Zoology and NERC’s Centre for Ecology & Hydrology (CEH), and colleagues studied its complex lifecycle.

Professor Thomas said: ‘For six years from May to late September I lived with the last UK colonies, measuring everything, including their behaviour, 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.’

As a result of this work the scientists found that the butterfly depended on a species of red ants [Myrmica sabuleti] for its survival. The team was able to pinpoint the cause of the Large Blue’s decline: changes in the grassland habitat, due to less grazing by livestock and wild animals, that led to a dramatic reduction in the population of red ants that the butterflies depend on. 

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.

Sir David Attenborough

Armed with this knowledge ecologists were able to restore the grassland habitat to its former state and, from 1983, Professor Thomas and co-author David Simcox from CEH began introducing Large Blue butterflies imported from Sweden to restored sites in the UK with the first native UK Large Blues emerging in 1984. In 2008 the butterflies occupied 30 per cent more colonies than they had in the 1950s, before the major decline began.

‘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,’ commented Sir David Attenborough. ‘It is, moreover, a tribute to the dedication of many practical conservationists who have skillfully recreated its specialised habitat in our countryside.’

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 woodlark, pale heath violet and the pearl-bordered fritillary.

A report of the research, entitled ‘Successful conservation of a threatened Maculinea butterfly’, is published online in this week’s Science.