Cats and small island conservation

Domestic cats have been in the news recently in Europe. Conservationists have been trialling some new techniques to try to limit the depredations of pets and feral cats on different wildlife species. There is no dispute about the volume of wildlife killed by cats, but what is not always clear is the extent to which this results in population declines of the species they are killing. Most species are able to tolerate the impact of this depredation, because they are evolved to cope with it.
The situation is different in small islands, especially those in which evolution has taken place in the absence of cats, or any other land mammals for that matter. It is plain that cats and small-island conservation do not mix. Worldwide, domestic cats have been responsible for the extinction of at least 33 bird species. This has often happened on small islands, with domestic cats becoming semi-wild, or feral, and finding the local birds and other wildlife easy prey.

Cats on the islands of Seychelles have dramatically reduced the range of and have been responsible for the extinction of species endemic to our islands. It has been suggested that the feral cat was the cause of the extinction of Magpie-robins on Aride and Alphonse islands, as well as serious declines on Fregate, which became the last refuge of the Magpie-robin. On Aldabra, feral cats have been observed to take turtle hatchlings.

Across the world, domestic and feral cats have now been removed from at least 48 islands, including four in Seychelles: Fregate, Cousine, Aride and D’Arros. They were removed from Cousine in 1986, helped by funding from BirdLife International and the support of the Seychelles Government and the island’s owner. On Cousine, cat density had reached an extraordinary 243 cats per square kilometre, three times the density that has been recorded on most other islands of the world.

The experience of Cousine Island has shown just how rapidly cats can multiply in a seabird island situation, spelling doom for the native and endemic birds, reptiles and other animals. Removing cats even from a relatively small island like Cousine is a major undertaking, require much skill, planning, resource and commitment. But the rewards for conservation are great, and Cousine has been testimony to that.

For successful cat removal on larger islands, it is now recognised within conservation circles that new and more efficient techniques used in combination with current techniques will likely be needed. This presents new challenges for conservation, for which the lessons learned from Cousine and other islands will stand us and our colleagues elsewhere in the world in very good stead.

In Seychelles, the SSPCA provides a free cat neutering service, for pets and strays. This service is invaluable both for animal welfare and for conservation, and provides at least some level of control of the ecological impact of cats.

Nature Seychelles, published on Regar Newspaper, 26 September 2005.

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