Bermuda's chief rat-catcher is using a mouse to sniff out the Island's rodents.

It is virtually impossible to know how many rats are living on the Island at any one moment but it runs into many thousands even by the most conservative estimate.

However, the appliance of a high-tech computer programme to map and track the rats has helped reduce the rodent population by around 40 percent in the past four years.

But there isn't time for any back-slapping just yet amongst the Island's pest control officers because it appears some daredevil rats are outwitting the computer system, staying one leap ahead by scurrying up telegraph poles and trapezing along the wires.

The bad news ? if you are a rat ? is that the next version of the rat-catching computer system will also show the location of telephone and power lines so that these sneaky routes can be taken into account when the rat-catching team plan where to lay poison bait traps.

Finding out where the rats are, and even predicting their movements so poison traps can be laid before the rodents show up at a new hunting ground, has proven a potent weapon in the armoury of the pest control team.

With a few clicks of a computer mouse, Environmental Health Officer David Kendell and General Foreman Russ Furbert can call up an interactive map of the Island to locate the latest reported rat sightings.

Using the customised software, Mr. Kendell, Mr Furbert and the rest of the team can run time-lapse sequences that show the movement of families of rats as they scurry from neighbourhood to neighbourhood.

The computer maps are so detailed they show the location of sewers, garbage dumps and other geographical landmarks that can assist Mr. Kendell and his team as they review the data and predict the likely movement of the rats.

Poisoned bait can then be laid to head off the rodents.

Bermuda's Department of Health has found the Geographic Information System (GIS) invaluable in the battle to eradicate the rats. The "blind spots", such as telegraph poles and power lines, will be addressed when the computer software is next updated.

This week Mr. Kendell gave a tour of the system.

Calls from residents are logged on the system and then investigated by members of the pest control team who go out to scour the area looking for reasons why the rats are being attracted to it.

A survey form is produced and, working with the residents, a plan of action is drawn up to remove rat-attracting features.

"Once we get reports we take the information and see if there is a likely source that is attracting the rodents," said Mr. Kendell.

"With condominiums we often find the trash is not being disposed off properly. Everyone needs to be vigilant with their trash and put it in a proper metal bin with a lid.

"A rodent problem can be the manifestation of a human problem with contributing circumstances such as avocado and banana trees with fruit dropping onto the ground and not being cleared away, dog mess, or too much dog and cat food being put out which attracts the rats."

Mr. Kendell said: "We do a survey of the area looking for these factors and how rodents are getting onto a property. It is important that we talk to the resident and get them to help address the root cause of the rodent problem rather than simply going along and putting down rat poison."

Simply putting a lid on a trash can can be enough to discourage the rats.

When tackling a rodent problem the pest controllers are focusing on the available food supply for the rats, where they are living and any access they have to human occupied building.

Mr. Kendell said: "When rodents get into a property they are destructive. They eat through wires and can cause fires and are incontinent. It pays to block up holes around pipes and stop the rats getting in before they do real damage."

Since the start of the year, Mr. Kendell's department has laid 9,500 pounds of rat poison. That is less than in previous years and an indication that the rat numbers are reducing.

There have been calls from 1,100 people since January reporting rat sightings.

For every single rat seen there must be at least four more that are not spotted, according to Mr. Kendell, indicating a possible rat population on the Island of more than 5,000.

The GIS computer software has been effective in year-on-year reductions in the number of rat sightings. So far in 2005 there has been a 22 percent reduction in call-outs.

But the need for vigilance by residents continues.

Mr. Kendell's checklist includes removing any accumulation of trash, putting lids on trash cans and using metal bins because rats can gnaw through cheap plastic.

He also asks that residents supervise the feeding of pets and don't leave out excess food, and remove dropped or rotting food from trees.

The Department of Health's rat-tracking computer system is impressive, but Mr. Kendell added: "The technology only takes us so far, then it is up to the public."