Whom to Blame – Cats or Rats?

Trophic roles of black rats and seabird impacts on tropical islands: Mesopredator release or hyperpredation? (2015) Ringler et al., Biological Conservation, 185.

Feral cats are responsible for the decline of many endemic species worldwide. But will removing them boost rat populations, causing more potential harm? (Image Credit: Brisbane City Council, CC A 2.0)

Guest post by Bart Peeters

THE CRUX

For centuries, rats have been portrayed as carriers of diseases and death; whereas our feline friends, worshipped by the ancient Egyptians, will definitely make your YouTube video go viral (a quick Google search of “cat video” shows 1 310 000 000 results). Both have been introduced, either accidentally or deliberately, to islands where endemic species have evolved and adapted to an environment without these generalist predators. So how do you know if eradicating one of them will make things better for the native wildlife?

Before taking radical conservation actions, it may be a good idea to understand how feral cats (the apex predator), rats (the mesopredator) and their common prey are affecting each other. Namely, if you kill all the cats, will there be more rats to prey on seabirds? On the other hand, will killing all the rats really reduce the predation by cats on seabirds?