A contraceptive against the proliferation of gray squirrels

British scientists plan to use a contraceptive for gray squirrels to reduce the number of these rodents whose proliferation threatens the very existence of the national species, red.

The animal, imported from North America at the end of the 19th century to populate large estates, has gradually taken over from its English cousin and also threatens several species of trees.

As part of a government scheme, scientists plan to administer an oral contraceptive, in their food, to gray squirrels. The project, tested in the north of England and in Wales, proved to be rather conclusive.

Some 70% of gray squirrels ate what was in small boxes placed in their natural habitat and designed in such a way that other animals could not access them. The idea now is to insert in these boxes a contraceptive in addition to food.

For Gideon Henderson, scientific adviser to the Ministry of the Environment, this contraceptive device, less aggressive and more effective than beaten or poisoning campaigns, is promising.

“It will help red squirrels (…) to return to their natural habitats while protecting British forests and increasing biodiversity,” he said.

“Without effective management, red squirrels could disappear from parts of the UK,” points out Vanessa Fawcett, of The Red Squirrel Survival Trust.

For the moment, no contraceptive has been used in the trials, but according to the scientists, it will be effective in both males and females.

The population of gray squirrels is estimated at 2.7 million in the UK, a number that is constantly increasing. Conversely, the country only has 140,000 red squirrels, the majority in Scotland.

More frail, redheads also need more space per individual and are threatened by squirrel pox brought by grays, which are immune.

Gray squirrels also threaten the health and survival of young trees, as they strip bark, weakening them and causing them to die.

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