Mutant rats in Gloucestershire are becoming increasingly resistant to common poisons, a university has discovered.
Scientists at Huddersfield University say that about 75 per cent of rats in the west of England have built up a resistance to the most commonly sold poisons.
Dr Dougie Clarke, head of biological sciences at Huddersfield University, said: "Some pest control companies are still using the same rodenticides - Bromadiolone and Difenacoum - in areas where there are resistant rats and things need to change.
"We're wiping out the normal susceptible rats and we're going to be left with resistant rats only in this area so alternatives have to be found so we're not using these poisons."
Experts believe the rise could be down to the incorrect dosages of poison being given, which are too low. Rats which are resistant to the poison get fattened up by the bait and those that survive then mate with other resistant rats, allowing a generation of rats resistant to existing poisons to build up.
Although the research is not complete, the scientists said within 10 years all rats in the Gloucestershire, Wiltshire and Bristol areas could be resistant to poisons.
