Domestic Cats as Invasive Alien Species Worldwide

Domestic cats have been recognized as one of the world’s worst non-native invasive species. Originally domesticated in the Middle East, they have spread globally, causing significant ecological harm. In the United States alone, outdoor cats kill approximately 2.4 billion birds annually, while in Australia, they are responsible for the deaths of about 377 million birds and 649 million reptiles each year.

Globally, cats have contributed to the extinction of at least 63 species, including birds, mammals, and reptiles. Their impact is particularly severe on islands where native species are ill-adapted to mammalian predators. The presence of cats disrupts ecosystems by predation, competition, and disease transmission, affecting not just individual animals but entire populations.