Britain’s most endangered butterfly thriving after decades of conservation efforts
The Large Blue butterfly which was declared extinct in 1979 is now flourishing again
Sarah Knapton, science editor
27 AUGUST 2016 • 12:01AM
The large blue butterfly which became extinct in Britain in the 1970s is finally thriving again following decades of conservation efforts.
Although overall butterfly numbers have slumped across the country this year because of the wet weather, the Large Blue has bucked the trend with the highest numbers seen for at least 80 years.
If the surge continues, Britain’s most endangered butterfly could soon return to its pre-extinction peak and be removed from the International Union for the Conservation of Nature red list of threatened species. It is currently the only UK butterfly on the list.
Large blue numbers have soared in the south-west England, and around 60 per cent of the population now lives at Gloucestershire Wildlife Trust’s Daneway Banks and Somerset Wildlife Trust’s Green Down, where decades of grassland management has finally paid off.
Some 10,000 butterflies have already been recorded this year and they have laid more than a quarter of a million eggs in the thyme and marjoram flowers, raising hopes of huge numbers in the coming years.
“This is fantastic news for this globally endangered butterfly whose extraordinary life cycle makes its conservation very challenging,” saidGloucestershire Wildlife Trust’s chief executive Roger Matlock.
“Scrub clearance and careful grazing of wildflower-rich grasslands is key to ensuring a future for this beautiful insect. This special management also helps a huge diversity of wild plants and other insects to thrive.”
Conservationists first noticed that the large blue was in decline in the early 1900s and by the 1950s only 100,000 adults remained in Britain. Despite efforts to save the species it was pronounced extinct in Britain in 1979.
But in 1984, scientists discovered that the butterfly can only survive in the nest of one species of red ant called Myrmica sabuleti.
The caterpillars produces scents and songs that trick red ants into believing they are one of their own grubs, and they are carried underground into the ants nest and placed with the ant brood.
They then spend the next 10 months feeding on the grubs before pupating in the nest the following year and then emerge to crawl above ground as butterflies.
However in the 20th century countryside management changed to leave grassland much taller than it had been, leaving the red ants struggling to survive. The loss of the red ants mean the butterflies also could not survive and their numbers plummeted.
But conservation efforts to restore grassland have allowed populations to re-establish and in the last year alone, numbers have risen by up to 74 per cent in some areas. Professor Jeremy Thomas, chairman of theRoyal Entomological Society’s Conservation committee and chairman of the Joint Committee for the Restoration of the Large Blue Butterfly, added: "The success of this project is testimony to what large scale collaboration between conservationists, scientists and volunteers can achieve.
“Its greatest legacy is that it demonstrates that we can reverse the decline of globally threatened species once we understand the driving factors."
Managing the grasslands to support the large blue is also helping other lost species to return to the south-west, including fly, frog and musk orchids. The Downland villa beefly – not recorded in the UK for 50 years prior to 2000 has also been breeding rapidly in Daneway in the past two years.
At Green Down in Somerset meadow brown and marbled white butterflies had their highest and second highest recorded numbers respectively in decades of recording.
Mark Green, the reserves manager for Somerset Wildlife Trust, added: “The amazing numbers of large blues recorded this year show what can be achieved through close partnership working and landscape scale conservation land management, underpinned by sound science.
“Large blue numbers had declined significantly two years ago, due to unfavourable weather conditions. But, thanks to the project partners creating and maintaining a number of well-connected core sites, the butterfly has now bounced back to record numbers.
“I feel proud to play a part in this highly successful project, which gives me hope that we can reverse the declines of other vulnerable species.”
Large Blue ©Keith Warmington