 To date , little scientific data is available to assess the impact of cat predation on prey populations . Even well @-@ fed domestic cats may hunt and kill , mainly catching small mammals , but also birds , amphibians , reptiles , fish , and invertebrates . Hunting by domestic cats may be contributing to the decline in the numbers of birds in urban areas , although the importance of this effect remains controversial . In the wild , the introduction of feral cats during human settlement can threaten native species with extinction . In many cases , controlling or eliminating the populations of non @-@ native cats can produce a rapid recovery in native animals . However , the ecological role of introduced cats can be more complicated . For example , cats can control the numbers of rats , which also prey on birds ' eggs and young , so a cat population can protect an endangered bird species by suppressing mesopredators . 
