By David Alderton

A U.K. university is investigating the impact of cats on local wildlife. Zoologists at the University of Reading examined the hunting behavior of 200 cats in different areas of the town. Their estimate is that the typical urban cat is responsible for killing 16 creatures a year.

By extrapolating this figure across the entire U.K., they have reached the conclusion that Britain’s feline population annually kills 92 million small creatures.

It is feared that cats could be having an adverse impact on the numbers of some bird populations as a result. The population of house sparrows (Passer domesticus), for example, has fallen by 60 percent since the mid 1980s, but most ornithologists believe that other factors are primarily responsible for the decline of these birds.

Further research is employing the latest technology, however; GPS tracking and data logging the cats in the survey will give better insights into their hunting habits.

Blaming cats for the decline of native wildlife is very easy, of course, but around the other side of the world, a very different story has emerged. Macquarie Island lies in the sub-Antarctic region of the Southern Ocean, south of Australia, and extends over an area of some 48 square miles.

Sailors visiting the island in the 1800s abandoned cats, and a feral population soon grew up alongside rabbits—another introduced species. The island is also home to a number of unique native species, including a race of the red-fronted kakariki (Cyanoramphus novaezelandiae), as well as penguins, and is listed as a World Heritage site.

Myxomatosis reached the island in the 1970s and began to decimate the rabbit population, which had provided the mainstay of the cats’ diet. At this point, the cats started to prey increasingly on other wildlife, so scientists decided to eradicate them. This cost $400,000 and took about 20 years, with the shooting of the island’s last 160 cats in the winter of 2000.

At this point, the rabbit population on Macquarie Island was under 10,000. Since then, however, their numbers have soared to more than 130,000 today, as the survivors developed immunity to the virus causing myxomatosis. They have now stripped rare plants, altering a third of the vegetation on the island, while their burrowing activities have changed the landscape, too.

Albatross breeding grounds on the upper slopes have subsided, with resulting landslips affecting penguin colonies on the beach below. The number of rats and mice brought here on ships and controlled in the past by cats has increased dramatically, too, eating the seeds of plants and exacerbating the damage caused by the rabbits.

This has now forced scientists to rethink. Dana Bergstrom, an ecologist from the Australian Antarctic Division, is advocating that a “broad ecological view” is necessary in such cases in the future, rather than concentrating on the removal of a single species.

The cost of this misjudgment and safeguarding the future of the island’s wildlife is now likely to add up to $20 million. Detailed planning is underway for the elimination of both rabbits and rodents during the winter of 2010. Helicopters will drop poisoned baits over the entire island initially, after which teams of hunters with dogs will seek to eliminate any survivors.

Back in the U.K., just as the Reading survey appeared, it emerged that rodent numbers were at a record high. The initial investigation was carried out over only a two-month period in the summer, when young birds and animals are most numerous and susceptible to predation, which almost certainly distorted the data. The unfortunate aspect of scientists making such claims, however, is that this can often lead to animal sadists targeting cats, as has occurred in the past when the media reported on this topic.

What is undeniable is that cats do vary significantly in their hunting instincts and abilities. Persians (and other breeds reared in catteries for many generations) are far less likely to have any interest in hunting. At the other extreme, a farm cat taught by its mother is likely to remain a formidable hunter throughout its life.

In Australia, promotion of Ragdoll breeds is one way to help safeguard the continent’s unique fauna, since such cats are reputedly disinclined to hunt. In some areas, curfews have been proposed, with owners being responsible for keeping their cats indoors overnight, when they would otherwise most likely to be hunting.

Retailers can play a part in helping to deter cats from preying on wildlife by promoting sales of items such as collar bells and ultra-sonic devices that emit a high-pitched sound, which some cats find unpleasant, so they avoid the bird-feeding areas. <HOME>

David Alderton is a freelance writer in the United Kingdom.