Caught on camera: The impacts of urban domestic cats on wild prey in an African city and neighbouring protected areas

Abstract

Domestic cats (Felis catus) have contributed to the extinction of indigenous species worldwide, but impacts in Africa are unstudied. We compare prey returned home from three questionnaire surveys (2009, 2010 and 2013/14) in Cape Town, South Africa, with footage from some of the same cats wearing animal-borne video cameras (KittyCams), to assess differences in actual predation vs. returns. Cape Town borders Table Mountain National Park (TMNP), so cats may prey on animals in a protected area. Urban edge (UE) and deep urban cats (DU) did not differ in predation rates, but the suite of species killed differed significantly. KittyCams revealed that most predation was nocturnal, and only 18% of prey recorded on video were returned home, thus cats kill 5.56 times more animals (averaged across all taxa) than returns data suggest. Reptiles constituted 50% of prey, but only 17% of returns; mammals constituted 24% of prey, but 54% of returns. Non-native species represented only 6% and 17% of animals killed by UE and DU cats, respectively, pointing to a high cost of cat predation for native fauna. Applying a correction factor of 5.56, the average domestic cat in Cape Town kills c. 90 (95% CI = 59, 123), animals.year−1. Thus, the approximately 300 000 domestic cats in Cape Town kill c. 27.5 million animals.year−1, and TMNP is likely to lose c. 203 500 animals to UE cats annually from within its boundaries. The scale of this predation necessitates conservation options to minimise impacts of cats on wildlife, particularly near protected areas.