Scientists study what the cat brought in

Wildlife researchers have hired the services of some unusual helpers: 200 neighbourhood cats equipped with electronic tags. The animals have been recruited in an attempt to discover how much wildlife destruction is wrought by feline pets.

Some experts believe Britain's 9m cats could be killing more than 150m birds, mice, rabbits, moles and other creatures every year. For species such as the house sparrow - whose numbers are dwindling sharply - cat predation could be a serious threat. Others, however, say cats mainly kill sick, weak or old creatures and are not a major problem.

The Reading University project, led by Rebecca Dulieu, a biologist, has been set up to provide answers, using electronic tracking and computing analysis to monitor cat movements in unprecedented detail. "We know what cats do in our homes - they sleep," said Dulieu. "But we have virtually no idea of what they get up to outdoors, particularly at night. Now we can find out. We have found our cats are bringing back, on average, 4.8 dead animals a year. Most are mice but there are also rats, dormice and shrews. Birds make up about a third of the total. One cat even brought back a weasel."



The kill rate found by Dulieu would therefore suggest that British cats bring back about 40m creatures a year to their homes. However, previous studies have also indicated that only 30% of dead animals are actually returned to homes. Large prey, such as rabbits, are too heavy, while very small creatures are usually eaten on the spot, for example.

That analysis suggests, in turn, that the average cat's annual kill record must be closer to 16 - which in turn suggests that about 145m wild animals are perishing at the paws and claws of the nation's feline population every year. However, even that figure may be an underestimate. Some studies put the cat's kill return rate at about only 20% - which would raise their overall toll even further, to almost 200m. "The trouble is that we do not have enough reliable data about cats' outdoor activities, especially at dark," said Dulieu. "We could be overestimating or underestimating their kill return rate quite significantly.

"For the first time, cats will be fitted with data loggers that will show their movements, range and behaviour 24 hours a day. We will know when one kills an animal - typically by the way it plays with its prey. We will then be able to work out precisely how many animals a cat is killing every year, and from that estimate a national figure. It will be a pretty formidable number."