Quantifying the presence of feral cat colonies and Toxoplasma gondii in relation to bird conservation areas on O'ahu, Hawai'i

Abstract Free‐ranging feral cats (Felis catus) are increasingly found in colonies loosely managed by people. These colonies increase cat densities and, hence, pose threats to wildlife via disease and predation, particularly in insular ecosystems where native species have smaller populations and reduced pathogen exposure compared to continental systems. Given such concerns, our objectives were to: (a) identify feral cat colonies on the island of O'ahu in the vicinity of important native bird sites; and (b) test for Toxoplasma gondii, a parasite‐causing disease (Toxoplasmosis) of concern to native birds, at cat colony sites. We identified 32 important native bird locations and surveyed public lands near these sites to determine presence of cat colonies. Where cat colonies were present, we collected feces and used molecular tools to identify the presence of T. gondii. We identified 25 cat colonies near an important bird area and collected feces at four of these colonies, with three testing positive for T. gondii. The presence of cats near a majority of native bird areas suggests that cats may impose a serious threat to bird species. Our finding of T. gondii at three of the four colonies where cat feces were collected raises serious health concerns for humans, birds, and many other terrestrial and aquatic organisms. Native birds in Hawai'i, including highly endangered species, are susceptible to both predation and T. gondii, and finding its presence in locations relatively near to important native bird areas provides further evidence that reducing free‐ranging feral cat numbers is critical for reducing impacts on birds.