OSLO—A blue butterfly died out in Britain 30 years ago because of disruptions to a life cycle that includes pretending to be an ant, according to a recently published study that points to smarter ways to protect wildlife.
Research into the large blue butterfly—now successfully re-introduced to Britain from Sweden—hints at how governments can use science to achieve U.N. goals of slowing a loss of animal and plant species, scientists said.
For decades, overzealous human collectors were blamed for dwindling numbers of the large blue until scientists found that wrong-minded conservation had let grass grow taller and made soils unsuitable for the red ants that its caterpillars eat.
"We discovered that the butterfly was much more specialized than anyone had thought," said Jeremy Thomas of Oxford University who led a study with British colleagues published in the journal Science.
"It only took the grass growing 0.4 to 0.8 inch taller for the species of ant it relied upon to be replaced by another," he said. Longer grass means more shade and can make the soil 3.6 to 5.4 degrees Fahrenheit cooler.
"To human beings the change looks like absolutely nothing. But when you are on the scale of insects, it makes a huge difference to the microhabitats where they live," he said.
The butterfly, which vanished from Britain in 1979, lays its eggs on thyme flowers and the caterpillars fall to the ground after hatching. They secrete chemicals and even make noises that make the red ants believe they are wayward grubs.
Gobble Grubs
The ants then mistakenly carry the caterpillars to their underground homes and keep looking after them even though the adopted intruders gobble ant grubs for 10 months before forming a chrysalis and flying away as adult butterflies.
In 1931, for instance, conservationists bought and fenced off an area in England to keep out butterfly collectors. But the fence kept out animals—such as cows and sheep—that kept the grass short. Myxomatosis among rabbits also let grass grow in some areas in recent decades.
Thomas said renewed grazing helped both the butterflies and other wildlife such as the pearl-bordered fritillary butterfly, the woodlark bird, and the pale heath violet flower.
The recovery of the large blue showed that better research into habitats, at risk from expanding cities or climate change, was a key to better conservation.
"The project tackled problems typical of many temperate butterflies that were disappearing from apparently suitable sites, and provided insights for quicker, cheaper approaches," the scientists wrote. The large blue butterfly and its relatives were selected in 1974 as one of three big test cases for conservation.
The other two were Queen Alexandra's Birdwing of Papua New Guinea, the biggest butterfly in the world with a 1-foot wingspan, and the monarch butterfly of North America, which migrates in millions to Mexico.
