Managing feral cats on a university's campuses: how many are there and is sterilization having an effect?

Worldwide domestic and feral cat (Felis catus) numbers have increased. Concerns regarding high populations of feral cats in urban areas include wildlife predation, public nuisance, and disease. This study aimed to estimate the size of the feral cat population on 5 campuses of the University of KwaZulu-Natal, South Africa, to determine whether sterilization has an effect and to make management recommendations. The study used both the total count and mark-recapture methods to estimate the feral cat population on each campus. The study chose a noninvasive method of taking photographs to "mark" individuals and record those who were sterilized. The study estimated a total of 186 cats on all campuses and density at 161 cats km(-2). There was a negative relationship between sterilization and numbers. Sites with higher sterilization showed a lower proportion of younger cats. At the average sterilization of 55%, the population, according to predictions, would remain stable at fecundity, survival, and immigration rates reported by cat caretakers. However, caretakers underestimated cat abundance by 7 ± 37 SD%. Caretakers' feral cat sterilization and feeding programs appear to provide a service to the university community. Key management recommendations were to increase sterilization to 90% to reduce the population over the long term and to raise funds to support the costs incurred by voluntary cat caretakers.