Like U.S. GIs during World War II, they're "oversexed and over here."
The gray squirrel — introduced to Britain from the United States in the 19th century — is now overrunning the countryside, out-breeding and out-eating its smaller British cousin, the red squirrel.
Conservationists said Monday they plan to test a contraception program in an effort to protect the indigenous species — who number only 160,000 — from the gray squirrels, 3 million strong and rising.
Scientists are experimenting with a "fertility control agent" used successfully in the U.S. and now being tried on a range of species, said a spokesman for the Scottish Executive, which is co-funding the research with the British government and the Forestry Commission.
Under the pilot project, contraceptives could be administered either in food or by injection.
"The project aims to test and adapt fertility control agents which have been used successfully in the U.S.," the spokesman said on condition of anonymity in line with government policy. "The materials are administered by injection, and recent formulations can render an animal sterile for a number of years with a single dose. "
The spokesman added that immuno-contraception would only be used in the wider population of squirrels if the pilot project proved successful.
Richard Wales, a conservationist with the group Red Squirrels in South Scotland, welcomed the project.
"Lethal control is currently the only way we have of controlling the grays, so it would be good to have an alternative such as contraception," he said.
Wales manages 23 woodlands across south Scotland where he nurtures a population of more than 35,000 reds.
Grays were first imported to Britain in 1876 when a pair was brought across the Atlantic as a wedding present. A fad for grays ensued, but many were released into the wild and the population has expanded rapidly ever since.
