Feral cats are a significant threat to native wildlife in Hawaiʻi. In addition to direct predation on nēnē and other native species, feral cats also spread the parasite Toxoplasma gondii, which can contaminate the environment and harm birds, mammals, and humans. Feral cats are known to prey on endangered species and are recognized as a major source of mortality for birds in the United States.

Toxoplasmosis is a particular concern for the conservation of endangered species like the nēnē, as well as the Hawaiian crow and monk seal. To address the threat of feral cats, it is important for pet owners to spay and neuter their cats, keep them indoors or safely contained, and microchip them for identification. Feral cats should not be fed and humane cat traps are available for loan from the Hawaiian Humane Society. Trapped cats can be brought to the society for spaying, neutering, and other health services, and should then be brought home as indoor pets, offered for adoption, or killed.