An increasing number of Britain’s rats are mutating to become immune to commonly sold poisons, scientists have warned. Research from Huddersfield University found 75 per cent of rats in Bristol, Gloucestershire and Wiltshire built up poison resistance, with the most serious mutations being seen in Bath and Wiltshire.
Experts say the rise is down to an incorrect use of poisons, where people have used dosages that are too low.
Rats which are resistant to the poison are fattened up by the bait, with survivors going on to mate with other resistant rodents. This allows a generation of rats that are resistant to existing poisons to build up.
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 solely with resistant rats in this area, so alternatives have to be found to these poisons.”
Wildlife experts are also concerned about the risk to other animals – especially cats – which may hunt the rats. The study aims to survey areas across the country and test samples from 600 rats. So far researchers have tested around 300 rats. Dr Clarke said that it is likely that all rats in Gloucestershire, Wiltshire and Bath could be resistant to poisons within ten years.