A spatial agent-based model of feral cats and analysis of population and nuisance controls

Abstract

Free-roaming feral cats are common in areas of concentrated human habitation, and can pose considerable threats of nuisance and damage to native ecosystems. Trap-neuter-return (TNR) and trap-vasectomy-hysterectomy-return (TVHR) are two humane methods for the reproductive control of feral cat populations. Both TNR and TVHR render a cat infertile, but cats that have undergone TVHR continue to produce hormones that drive mating behaviors. We built a stochastic agent-based computational model for simulating the survival, reproduction, and movement of individual feral cats and the use of TNR and TVHR to modify cats’ reproductive abilities and behaviors. Daily movement of cats between colonies is implemented based on the distance between colonies and landscape properties (e.g. rural, urban). Spatially targeted TNR and TVHR policies are evaluated using two management goals: (1) reduce total population size and (2) reduce nuisance attributed to feral cats. Nuisance includes spraying and noise, both of which are associated with un-neutered males, as well as population abundance. Results indicate that both TNR and TVHR have the potential to greatly reduce population size. Effectiveness of each control depends on the capture rate, number of colonies targeted, size of each colony, and movement of individual cats between colonies. Results show that on average TVHR performs moderately better than TNR at reducing population size, but TNR substantially outperforms TVHR in reducing multiple nuisance measures.