The influence of Feral Cats Felis catus on the distribution and abundance of introduced and endemic Galápagos rodents

Abstract

The impact of feral cats on the distribution and abundance of endemic and introduced rodents in the Galápagos Islands, Ecuador was assessed by sampling the rodent fauna of islands with and without cats. All islands where endemic rodents are known to have previously occurred were sampled. No new species of rodent or species considered extinct were recorded, but all species of endemic rodents believed to be extant were recorded. All islands sampled had rodents, but no endemic rodents were recorded on islands with cats. To examine whether endemic rodents had a potentially higher susceptibility to predation by cats compared to introduced rodents, the aversion of rodents to the scent of cats was tested by placing dried cat faeces on every second trap at each site trapped and the difference in trap success between endemic and introduced rodents compared. Introduced rodents on islands with feral cats were significantly less likely to enter traps with cat faeces compared to endemic and introduced rodents on islands without cats. This suggests that Galápagos endemic rodents may be more susceptible to predation by cats than introduced rodents because of the lack of an innate aversion to cats.