Who would have thought domestic cats can be a danger to other species?
[VICTORIA 14/03/2008] About 10 years ago I had an unnerving experience soon after one of the most thrilling ones. I was undertaking a biological assessment of Marianne Island in May 1998 with Steve Parr of the RSPB. On the first day we saw a Vev or Seychelles Paradise Flycatcher perched on a tree. This was the first time a Vev had been seen on Marianne since 1936. It was a fantastic discovery. But then I also saw a feral cat in a nearby tree. I feared the cat could after this rare bird.
Domestic cats have been responsible for the extinctions of at least 33 bird species worldwide. Most of these extinctions happened on small islands. On many small islands, endemic species have evolved in the absence of predatory mammals like cats and rats. They have major difficulties coping with predators when these are introduced either by accident or by design.
It is sometimes difficult to understand the precise impacts cats may have on populations of threatened species. The Paradise Flycatcher seems to cling on in the presence of cats and rats on La Digue. On smaller islands the impacts of cats can however be disastrous.
Cats have often been introduced to islands in an attempt to control rats which also have a major influence on island wildlife. Scientists say it is sometimes difficult to separate the negative effects of rats and cats on wildlife because on most islands both species are present.
The first settlers probably introduced cats to Seychelles. Cats have reduced the populations and distribution of several of our endemic species. In fact they are thought to have been responsible for extinctions of Magpie-robins on Aride and Alphonse islands as well as population declines on Fregate. Fregate became the last refuge of the species.
Cats have been removed from at least 48 islands around the world, including Fregate, Cousine and Denis islands in Seychelles, for the purpose of conservation of native island fauna. They were removed from Cousine in 1986 under a program funded by BirdLife International. There, cat density had reached an extraordinary 243 cats per square kilometers, three times the density recorded on most other islands of the world.
This shows just how rapidly cats can multiply in a small island situation. Removing cats even from relatively small islands is a major undertaking, requiring much skill, planning and resources. It also goes against the grain of people interested in animal welfare. But the rewards for conservation are huge. Islands like Cousin, Cousine and Fregate have a tremendous wealth of biodiversity, usually only possible in cat and rat free situations.[ENDS]