Your cuddly cat may be a killer

THE world population of the Stephen’s Island wren was wiped out by Tibbles, the lighthouse keeper’s cat.

Actually, there were a few other cats on the island and Tibbles may not be responsible for all of the carnage’ but are you harbouring a similar killer in your home? Recent research in the United States suggests that you may be.

Kerrie Anne Loyd and Sonya Fernandez of the University of Georgia wanted to assess the damage to wildlife wrought by house cats. Some cats present their victims to their owners but do all of them do this? Even it a cat does so, is everything it catches brought home? If your pussy never displays trophies, can you be sure he’s innocent?

What owners say about the behaviour of their pets is not reliable. You can’t interrogate cats, so the researchers resorted to ‘kittycams’.

Advertisements were placed in local newspapers in Athens, Georgia, asking owners who allowed their cat to roam outdoors to take part in a study. About 60 feline devotees volunteered. All of the cats were given a free health check. Then a collar was fitted to each of them and a miniature video camera attached to it. After the cats’ forays, their owners downloaded the footage from the kittycams.

The criminal activities in which the naughty pussies indulged were revealed for all to see. The experiment continued throughout all four seasons.

The cats, it turned out, were on the prowl for an average of five to six hours per day. Not all of them, however, proved to be delinquent; only 30% actually caught anything. These made a kill, on average, once every 17 hours in the field. The number of victims was 2.1 per cat each week, a much higher predation rate than previous thought. Only 23% of catches were taken home for display so, if you believe your pet is whiter than white because it doesn’t do this, think again.

Prey included rodents, frogs, lizards and small snakes. Bird kills accounted for 13% of the total. Loyd and Fernandez estimate, on the basis of these results, that cats kill around four billion animals each year in the US. Five hundred million of the victims are birds.

But house cats are only part of the problem. Feral, or ‘stray’, cats were not included in the Georgia study. Not being pampered and fed by doting owners, they have an even greater incentive to hunt.

Aaron Hildreth and colleagues at the University of Nebraska, in a report entitled Feral Cats and their Management, claim that there are about 60 million stray cats in America, although they don’t say on what this estimate is based.

Thirty-three bird species, they believe, have been rendered extinct worldwide by feral cats.

What light can the American studies throw on the Irish situation? There are no reliable estimates for the number of domestic cats here but we can hazard a guess based on British figures.

According to the Mammal Society, there are about eight million house cats in the UK. The estimate for feral cats is 800,000, with an unknown number of others which have ‘loose associations with households in urban areas’. The British cat population, therefore, is in the region of nine million. Cats, incidentally, are twenty times more numerous than stoats and there are 38 times more of them than foxes.

Assuming that cat owning patterns here are similar to those in the UK, we have 600,000 to 700,000 house cats in Ireland. The ISPCA claims that there are about 200,000 feral ones. The Irish feline population, therefore, may be close to nine hundred thousand. If the predation rate of an Irish cat is similar to that found in the Georgia study, almost four million birds are killed by cats here each year.

What can we do to reduce the slaughter? Studies in Britain show that cats wearing bell-collars kill fewer birds. Keeping cats in at night is also effective.

As to whether putting out food for birds increases the risk from cats, the jury is still out. Cats learn to target birds at feeders but, on the other hand, there are more avian eyes and ears in the garden to spot a predator and raise the alarm. Also, if food is made available at a cat-proof table, a bird need spend less time foraging on the ground, where it’s vulnerable to ambush by a cat.