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Last Updated: Friday, 10 September, 2004, 06:45 GMT 07:45 UK
Waging war on the super rats
Greig Watson
BBC News Online, East Midlands

A rat in a house
Rats are drawn to sheltered areas with plentiful food
They carry a myriad of diseases, can breed five times a year and probably live close to you.

For many people, the UK's 60m common (or Norwegian) rats inspire a unique hatred and the immediate response to any trace of their presence are trays of vividly coloured poison.

But these "rodenticides" are becoming less effective and their impact on the wider environment increasingly regarded as unacceptable.

Now more sophisticated methods are being pioneered to understand how rats live, breed and can be controlled.

Mark Lambert, from the Central Science Laboratory, said the present methods of control leave a lot to be desired.

Using traditional rodenticides is cheap and easy but not necessarily the most effective thing to do.

"People would just put down the poison and forget about it, which would kill rats but did not address many other problems.

"Firstly, a lot of rats might die but if the habitat remains, there is a good chance other rats will reoccupy it.

Formidable Enemy
Rats on a farm
Rats are great opportunists and breed phenomenally fast
Mark Lambert, Central Science Laboratory
"If you keep putting down poison, it will eventually get into the environment and into the food chain, endangering other species.

"And there is also the classic problem of rats becoming resistant to the poison."

Mr Lambert said individual rats do not develop resistance but are either born with it or not.

With extended exposure to poison, resistant rats breed while others die off, leaving a resistant population.

"So to tackle this, we went back to basics. Rats are great opportunists and breed phenomenally fast. So why isn't everywhere overrun with them? Why are some places still relatively rat free?

"Once we had an idea why rats favour some places and not others, we could replicate an environment which the rats didn't like."

Mr Lambert began to concentrate his attention on farms.

Wide, grassy field margins were seen to favour small mammals, like common shrews and bank voles, and is a habitat less attractive for rats.

Growing problem

These borders also have other environmental benefits, creating buffer zones to absorb pesticide run-off, and attracting rat predators such as the barn owl.

Mr Lambert also found that to avoid predators, rats tend to avoid open spaces whilst on the move.

Removing cover around farm buildings, by clearing debris, machinery and stockpiled materials, led to reduced rat activity and survival.

Professor Robert Smith from the University of Leicester and chair of the Rodenticide Resistance Action Group, said: "Resistance to rodenticides has again emerged as a problem in some parts of England.

Environmental Impact
High levels of poison have been found in Red Kite
They (the poisons) get into the food chain and can kill other wildlife
Tony Stephens, Rentokil
"Rodenticide manufacturers have not come up with any new compounds and government departments seem to have other priorities.

"Mark's research has shown that good housekeeping by farmers pays dividends in keeping rats down, which is good for both the farmer and consumers of food produced by British farmers."

A survey found significant traces of rat poison in over 60% of the rare red kites and about 40% of barn owls.

Hygiene firm Rentokil has pledged to reduce its use of traditional rat poisons by 75%.

Tony Stephens, a biologist at Rentokil, said: "Our advice is that prevention is better than cure.

"Proof your building, filling holes and don't leave food out. Use a wheelie for rubbish and if you don't have one of those, leave bags out for as short a time as possible.

"Rat populations are not just becoming resistant to the poisons, it's a question of the poisons becoming less suitable.

"They get into the food chain and can kill other wildlife. Businesses, especially pubs and restaurants, don't want to use poisons.

"There is a real need to come up with alternative, holistic approaches.

"Rodenticides will still be used, but as part of a package, which looks at habitat, food sources and other types of traps."

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26 Aug 04  |  Manchester
Residents demand action over rats
03 Jun 04  |  Cumbria
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01 Mar 04  |  Health
Rat poison threatens birds of prey
17 Feb 03  |  England


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