Effects of sterilization on movements of feral cats on Catalina Island in California, USA

With the threats that feral cats impose on wildlife, including being opportunistic predators, competing with native predators, and often carrying zoonotic disease, population management of feral cats is immensely necessary. Trap-neuter-release (TNR) is a current popular method of management; however, due to little comprehensive documentation of the effects of TNR programs on wildlife, their success are difficult to assess.

To assess the effect of sterilization on cat movement, Darcee Guttilla and Paul Stapp tracked the movements of sterilized and intact cats on Catalina Island in California, USA. Evaluating fourteen sterilized cats, half male and half female, and thirteen intact cats, five males and eight females, Guttilla and Stapp found that home range sizes differed significantly only between males and females and not between intact and sterilized cats. Similarly, home ranges of males overlapped with the home ranges of other cats of both sexes significantly more than the homes ranges of females overlapped with each other. Females also traveled farther than males on average, but not enough data existed to determine significance, as demonstrated in (b) below.

In light of the results of this and other studies, Guttilla and Stapp suggest the TNR may do nothing to alleviate predation-related threats to wildlife. However, since diseased cats are not reintroduced into the colony after trapping, TNR does reduce some zoonotic disease threats.

Guttilla, D. A., & Stapp, P. (2010). Effects of sterilization on movements of feral cats at a wildland-urban interface. Journal of Mammalogy, 91(2), 482-489.

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