Cats are one of a suite of introduced species that have played a significant role in the extinctions and declines of Christmas Island fauna; these introduced species continue to exert pressure on many native species. In response, the Australian Government is undertaking actions to control the impacts of several introduced species; one of these actions is an island-wide cat eradication program. When several introduced species are present on an island, eradicating one species can cause changes to the populations of the remaining invasive species. For example, on other islands cat eradications have sometimes led to increased abundances of rabbits and rats, with knock-on consequences for native vegetation and fauna until the rabbits and rats were controlled. This project seeks to understand the likely impacts of cat control on invasive rats, and on the native species that rats prey on. The research will inform strategic management to optimise the outcomes from cat control on Christmas Island.