LONDON – This week marks the 25th anniversary of the large blue butterfly’s reintroduction to the UK. To celebrate, decades of research carried out by lead researcher Jeremy Thomas from the University of Oxford, and the Centre for Ecology and Hydrology in Wallingford will be published for the first time this week.
Barnaby Smith from the Centre for Ecology and Hydrology, told The Epoch Times, “It’s one of the very few, if not the only, conservation story in the world where they actually had scientific evidence [from the research] to get it right first time, rather than trial and error or guesswork.
“We haven’t really had a chance to do enough monitoring, to see what’s going on with the lifecycle or the countryside management that needs to take place to keep those species alive and happy and increase the numbers, but with this species, they had all that so this is very much a science- led conservation story.”
Since the 1950s, the population of the large blue butterfly, Maculinea arion, steadily declined until they were extinct in Britain in 1979.
“What happened with the large blue, they were lucky enough to catch the tail end before it became extinct ... and monitored exactly what was going on and isolated the two or three very important things they needed to do with the landscape to reintroduce it. Although it did become extinct, we were able to bring it back five years later and build up what’s now in the UK, a thriving colony of butterfly.
“The butterfly itself actually uses one distinct species of red ant to go from caterpillar to butterfly, so the first thing you have to do is create a landscape with the right kind of grass height and grazing with red ants. Once you’ve got the red ants back, you can reintroduce the large blue butterfly.”
Prior to this discovery, it was thought that the butterfly collectors had caused the population to decrease rather than their complete dependence on red ants. Thomas revealed that adult blue butterfly females lay eggs on thyme flowers in the summer. The hatched caterpillars fall to the ground and secrete chemicals mimicking those of red ant grubs. The red ants, attracted by the chemicals, will then carry them into their underground nests, where they will stay for ten months and feed them until they become butterflies.
Thomas said, “From May to late September [1979], I was living with the last UK colony, measuring everything, including their behaviour, how many eggs they laid, the survival of individual eggs, how many caterpillars were in the plants. It was a bit like a detective story.”
They realised that the grass in the butterflies’ habitat had grown too long, as farmers had gradually stopped grazing their livestock on the hillsides. In addition, a viral infection had killed many of the wild rabbits in the 1950s. Eventually, the overgrown grass caused soil temperatures to drop and ant numbers to diminish, which in turn affected the large blue butterflies.
“Human beings are so much larger than insects... what to us is an imperceptible change in habitat can have devastating consequences for a species like the bizarre and beautiful large blue butterfly. A difference of a centimetre in grass length can change the soil temperature by 2 or 3°C. If you’re the size of an ant or butterfly that difference is massive,” said Thomas.
Starting in 1983, the researchers began introducing large blue butterflies imported from Sweden into restored habitat sites such as Collard Hill, a National Trust reserve in Somerset. 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 decline by 2010. The next step is to revive other populations in Europe.
References
Successful Conservation of a Threatened Maculinea Butterfly. Science, June 18th, 2009.
