Year of the rat: Meet the verminators

Britain now has more of them than people – and your four-legged foes might soon be popping round for a bite. Sophie Morris visits the verminators whose hi-tech arsenal has got rodents on the run

(AP)

Andy Brigham chuckles as he reaches for a crude wooden apparatus that was used to kill rats in centuries past. It is not dissimilar to a guillotine, but with a shutter designed to flatten the whole rodent rather than simply severing its head, and is a grim device, but one that clearly amuses Brigham.

As a zoologist, Brigham has found a niche that, it's safe to say, few aspiring scientists dream of. As the man responsible for designing and selecting the potent products in Rentokil's arsenal, he is the terminator, or rather exterminator, of rats, mice, bedbugs, cockroaches and all kinds of other creepy-crawlies across the world.

Over the next few months, you might just find yourself in need of one of Brigham's devices. There are now more brown rats in Britain than there are humans. The latest estimates suggest there are 80 million of them – an alarming 39 per cent rise since 2000. The flooding in the past year has left many sewers cracked, and now the rodents are coming in from the cold.

If these figures seem apocalyptic, they can be explained by the rampant breeding capacity of rodents: an initial coupling can generate up to 2,000 creatures in just one year. And yes, they do carry all sorts of diseases – salmonella, tuberculosis and Weil's disease among them. Moreover, 7 per cent of household fires are caused by electrical cables that rats have chewed through.

Around the walls at Rentokil HQ are traps and baits of all kinds, live rats and mice in cages, stuffed stoats, weasels, moles and even a coypu from South America (which looks a bit like a small beaver). The ambience is not a little creepy.

Replacing the wooden trap on the shelf, Brigham brings down his latest weapon in the war on rats. Dubbed the "Radar" (Rodent Activated Detection And Riddance), this white box, about two feet long, is the most hi-tech weapon Brigham has so far developed. As a rat enters the trap through one of the holes at either end, it is detected by pressure-sensitive pads. Doors spring shut, covering both holes.

Next, the "despatch" – to use Brigham's preferred term. Rather than using edible poisons, the trap releases a dose of carbon dioxide, harmless to humans, but enough to suffocate the rat. "The CO2 has a narcotic effect on the rodent, which puts it to sleep very quickly," explains Brigham. "It changes the pH of the blood, which causes the body to shut down, which usually takes about 15 seconds, and then it dies within a minute. They feel something, but it's momentary."

Carbon dioxide is not only humane, it is also green, in that it eliminates the need for toxic bait, which can find its way into water sources or the food chains. More importantly, with the Rat Radar, the problem is contained, smell-free, and without mess. You won't have the problems of dead rats decomposing beneath the floorboards, as you can get with traditional baits.

Finally, and this is the really clever part, the trap sends a text message or email to Rentokil, notifying them that there's a rodent to be collected.

Another version exists for mice – though, adding to its hi-tech credentials, the Mouse Radar Mk II detects the mouse through two light beams rather than pressure pads, since a mouse's paw is so light.

Both Radar systems are generally used for commercial jobs in highly sensitive environments – such as food factories. They can be used in homes, but they will add a few hundred pounds to the cost of the job. Still, give it a few years and they'll be standard-issue from Rentokil, who see the technology as one way to keep ahead of the competition, or "Bulgarian with a bucket of bait", as the company's managing director, Jeb Kenrick, describes it.

But catching and killing is only half the battle. "The first and most important step," says Kenrick, "is detecting the infestation. Traditionally, that has involved someone walking round the premises, looking for evidence of rats." Therein lies the problem. Aside from the odd bold one, rodents don't hang around when they hear footsteps.

As is often the case with invention, the solution came from an existing problem. "One of the most common problems that security experts encounter," says Kenrick, "is that the burglar alarms for commercial premises or large blocks of flats are triggered by pests."

That got Brigham and his colleagues thinking. Could they produce an infrared detector, similar to the ones fitted to security lights, but capable of picking up rats and mice? By adjusting the sensitivity levels of existing technologies, Rentokil has created just such a system. These devices are the cutting edge of Rentokil's equipment, and they might already be fitted beneath the aisle of your local supermarket, or in the factory where your lunchtime sandwich was made. Kenrick suggests that it may be three to five years before they have enough of the detectors to offer them on domestic call-outs, but they would be perfect for lofts, the gaps beneath kitchen cupboards, or under the floorboards.

If you're tempted to go down the DIY route, there are a few things you ought to know. First, the myth that poisoned rats will go outside to die are just that – ask around and someone is sure to have vivid recollections of the hideous smell of decomposing rat, and the hassle involved in tearing up floorboards. And anyone with children, cats, dogs or rabbits clearly need to be careful. Kenrick explains that poisons intended for rodents should never be fatal to humans – once the rat-killing aspect for poisons is developed, a separate step in the design process is dedicated to making humans vomit. Consumption may result in a nasty throwing-up episode, but getting the poison out of your system might just save your life. "Still, it's not something that I'd want my children – who are four and six – to go through," he adds. "To pets, though, rat poison can be fatal, or do serious damage."

Now, the most common way of trapping rats is with a bait of specially formulated paste, which is placed inside a plastic box to discourage other pests having a nibble. The paste was developed because, while messier than a solid block of bait, both rats and mice are more likely to sample a bit. Still, new blocks made with bromatrol – a blue, rodenticidal concentrate – have been developed too, using a waxy formulation that is proving quite palatable. Rats have to eat most poisons three, four or even five times before they have the ultimate desired effect. A new development called "One Kill" is now available, although, naturally, it carries a higher risk and is mostly only ever used in cases of severe commercial infestation.

The other DIY alternatives include standard cartoon-style guillotine traps, which are considered highly ineffective because the rodent will often not approach the trap for days. You can increase the potency of these by placing them against skirting boards, and by using chocolate rather than cheese. Sticky boards have been banned in some European countries, because they are perceived to be cruel. More pertinently, they present some gruesome challenges: how to deal with a rat stuck to a board without splattering guts up the walls, or how to catch a three-legged rat that has chewed through its own leg to win its freedom.

One product Rentokil turned down was the Nooski, an invention from New Zealand, which lassoes a rodent with a rubber band, strangling it. Although the developers point out that it kills most targets within 30 seconds – much quicker than many products on the market – it would take some plastic band to kill a 22-inch-long rat, the largest that Paul Donnelly, who works for Rentokil pest control in central London, has ever heard of.

After 10 years in the business, Donnelly has learnt that, hi-tech developments notwithstanding, some jobs call for nothing more than brute strength. One involved a lone rat in a woman's kitchen. During his visit, the client, holding her newborn baby, became hysterical. Donnelly simply stepped on the rat and took it back to his office for incineration. But please don't try this at home. At least, not in your slippers.

How to keep them at bay

1. Don't attract mice or rats with food – where possible, store food in plastic or metal containers.

2. Regularly clean under cookers, fridges and cupboards.

3. When setting traps for mice, do not use cheese as bait – rodents actually prefer chocolate! Be careful when using household bait, as this can also encourage rodents to enter the home.

4. Seal up any holes, both inside and outside the home. A typical house mouse is able to enter a home through a hole that is the diameter of a ballpoint pen (6mm across).

5. Ensure any household refuse stored outside is kept in closed bins. Do not put meat into compost heaps and use squirrel-proof bird feeders.

6. Do not leave food outdoors for your pets for long periods. All residue should be cleaned away from bowls, as this will provide an additional food source for rodents.

7. Flooding can cause rats to come up from sewers through broken pipes. Ensure all pipe-work is in good working order.

8. Clean and maintain drains regularly to avoid infestations, and unblock gutters and water gullies.

9. Check outside decking for mice or rat nests. Dry, outdoor areas are a popular nesting place for rodents and need to be checked regularly.

10. If you have a problem in your house, seek professional treatment immediately to prevent large-scale infestations. Rat and mice colonies spread quickly.