Birth control for grey squirrels

The chubby grey squirrel can store more fat for the cold winters

Scientists at the Forestry Commission are trying to come up with a plan to make grey squirrels infertile.

The grey population is threatening the survival of the smaller red squirrel, competing for food and passing on a deadly disease.

It is hoped that lacing food with drugs that hamper fertility will bring the population under control.

The government has ruled out a national cull, citing the expense and questions about whether or not it will work.

Red squirrel risk

The work by the Forest Research division of the Forestry Commission is part of a three-year project to try come up with a successful method of oral contraception to be fed to the rodents without affecting other wildlife.

Brenda Mayle, one of the researchers involved, said the challenge is coming up with a food bait that the squirrels will be tempted to eat right away, rather than hide until later, as is their habit.

"Possibilities include wholewheat and smaller grains," Miss Mayle said, adding that peanuts and acorns have to be avoided in the search for a way to get the squirrels to ingest enough of the drug to be effective.

She added that any curb on the grey squirrel through contraceptives would only be one tool in the battle to contain the booming population - any breakthrough on the science side will not be ready for use for at least another five to 10 years.

"This is not the sort of thing we could do overnight," she said of the ongoing testing, which needs to find a way to deliver the drugs - which she did not identify - without endangering too many other animals.

"It is not an alternative to lethal options. The concept of eradication has come up a number of times, there have been bounty schemes, but that has been found to be ineffective."

The Department for Environment, Food and Rural Affairs, which is helping to fund the project along with Scottish Natural Heritage, has already stated that growth in the grey squirrel population has to be halted.

"The government is committed to preventing the further spread of grey squirrels, but eradication at national level is considered impracticable," a spokesman for Defra said.

Stand the cold

The explosion in the number of greys in recent years has led to fears that red squirrels could eventually die out in Britain.

Grey squirrels cope better with cold winter temperatures, mainly because they are larger and can store more fat.

The biggest concern with the grey is that it is a carrier of a virus known as squirrelpox, which is harmless in greys, but deadly for red squirrels.

Miss Mayle said despite some popular belief to the contrary, grey and red squirrels cannot crossbreed.

Ross Minett of Edinburgh-based Advocates for Animals said his group supports the idea of research into humane sterilisation but with conditions.

"We think it is an interesting idea and we welcome it being pursued," he said. "But we would expect it to be used as an alternative to killing."

Mr Minett said the ongoing regional culls are inhumane and ineffective.

Regional culls have been in place for some time in a bid to save the red squirrel, but no national eradication plan has been created, despite complaints that they are seriously damaging the countryside.