Objective: To examine demographic differences during a 1-year observational period between urban feeding groups of neutered and unneutered free-roaming cats following a trap-neuter-return procedure.
Design: Natural-setting trial. Animals-Free-roaming adult cats (n = 184) and kittens (76) living in 4 feeding groups in an urban region of Israel.
Procedures: Cats in 2 feeding groups were subjected to a trap-neuter-return (TNR) procedure. Cats in 2 other feeding groups were untreated. Data were collected on a weekly basis before and during feeding time over a 1-year period. Following individual cat identification, presence of adults and kittens was recorded throughout the year. Rates of immigration, emigration, and kitten survival were compared between neutered and unneutered groups.
Results: The number of adult cats in the 2 neutered groups increased significantly during the study period because of higher immigration and lower emigration rates than in the unneutered groups, in which the number decreased. In the neutered groups, annual presence of neutered cats was significantly higher than that of sexually intact cats. Kitten survival in the neutered groups was significantly higher than in the unneutered groups.
Conclusions and clinical relevance: Targeting the TNR method mainly at feeding groups in urban residential neighbourhoods may result in increased group size, as a consequence of 2 major changes in group dynamics: sexually intact cats immigrate into the neutered groups more readily and neutered cats reduce their emigration rates, possibly because of a reduction in reproductive and competitive pressures. To maintain a high proportion of neutered cats in such cat groups, persistent TNR campaigns are therefore necessary.