Contraceptive vaccines may be used to control the number of wild boar in the English countryside. The animals, which until recently had been extinct in Britain for at least 400 years, have been steadily rising in number in three main locations after a series of escapes from farms, and there is increasing concern that they may damage crops, spread disease and attack other animals – or even people. A big male can weight 400lb and has razor-sharp tusks.
A two-year government study reported earlier this year that wild boar did not present a national threat and there was no need for a national campaign of eradication – but it did recognise that local communities and landowners might want to deal with animals in their area.
As part of continuing research into how to tackle them, scientists have been giving contraceptive injections to female wild boar in the feral population in the Forest of Dean in Gloucestershire and then radio-tracking them to see if the contraceptives have any unwanted side effects – such as making them more aggressive.
The contraceptives are known to be effective – it is the side effects that are the subject of the tests. The experiment, which has been going on for two years, has just been extended for a further three, and if it is successful, could be extended to other wild or feral animals, said a spokeswoman for the Department of the Environment, Food and Rural Affairs (Defra).
The obvious candidate would be the grey squirrel, the American import that has driven the native red squirrel out of most of England, but Defra said it was too early to talk about which other species might be considered.
The Forest of Dean boar population is the second largest, consisting of about 100 animals. It has hit the headlines more than once with encounters between boars and people. In January this year, a boar was shot in the playground of Ruardean primary school, after it turned on a forest ranger, while in nearby Cinderford, in 2004, a boar thought to have escaped from an abattoir charged through a supermarket and knocked down an old woman before fleeing into the countryside.
The largest boar population, on the Kent/Sussex border and is thought to number more than 200 animals. It appears to have started when fences of several boar farms were blown down during the great storm in October 1987. The smallest is centred on Powerstock Common in west Dorset, and is thought to consist of fewer than 50 individuals.
However, all the populations are steadily expanding and, after the Government report earlier this year, Rob Guest, from the Forestry Commission, said he thought culling was an option that would have to be considered. "I think what is clear – because of the potential for the population to explode – there is going to have to be some sort of management," he said.
The current experiment is being carried out by researchers from the Central Science Laboratories who catch boar sows humanely in big cage traps that have been baited. They are recaptured from time to time for blood tests. The injections could prevent the sows from having up to 15 piglets at a time.
"It is important there are effective and humane methods available to resolve conflicts between wildlife and humans," Defra said, "Fertility control is one such method, and currently between six and 12 wild boar are being radio-tracked as part of a study to test the effectiveness of immuno-contraceptive vaccines on wild animals.
"Whilst it is preferable for the wild boar being tracked not to be shot, if these individual boar are causing damage on private land, landowners can control them. All we ask is that if a wild boar involved in the study is shot, the landowner returns the radio collar to the Central Science Laboratory."
*Birth control for wild animals, especially invasive non-native species that harm their new environments, is definitely on the agenda. The Forestry Commission is in the middle of a three-year trial to see if contraception can be made to work with grey squirrels. One of the challenges for researchers is to come up with a bait that squirrels will to eat immediately, rather than squirrel away for later, as is their habit.
In Australia, syringes on poles have been used to inoculate koalas with contraceptives without them even leaving their trees. In 2004 authorities in Australia's capital, Canberra, used contraceptives hidden in grass to limit the number of kangaroos in the city.