THE DIET OF CATS, FELIS-CATUS, ON CHRISTMAS-ISLAND, INDIAN-OCEAN

Cats, Felis catus, were taken to Christmas Island (10 degrees 25'S,105 degrees 40'E) in the Indian Ocean at the time of first settlement in 1888 and a feral population became established soon thereafter. In 1988 a wide range of vertebrate and invertebrate animals was present in the diet of these feral cats, but flying-foxes, Pteropus melanotus, fruit pigeons, Ducula whartoni, and introduced rats, Rattus rattus, together constituted 80% of their food intake by weight. Of the guts examined, 45% contained R. rattus, and this species accounted for 31% of food intake by weight. Less than 10% of cat guts contained P. melanotus and D. whartoni, but the large body weights of these species meant that by weight they made up 21% and 28% respectively. Mus musculus was found in 27% of guts examined, although it contributed only 2% by weight. It is likely that the large numbers of feral cats present in vegetative regrowth on mined areas are related to the ease with which all four primary prey species may be caught there. No evidence was found that cats are having a deleterious effect on native species and they may well be beneficial in stabilising the numbers of R. rattus, which itself can be a serious predator of nesting birds.