Estimating free-roaming cat densities in urban areas: comparison of mark-resight and distance sampling

Abstract

Obtaining reliable population estimates is imperative in managing wildlife populations, particularly when attempting to implement nuisance control measures. Free-roaming cats ( Felis catus ) impact wildlife worldwide through predation, competition and disease transmission. Ideally, measures of controlling free-roaming cat populations should be evaluated a priori, which requires obtaining population estimates for use in population control programs (e.g., euthanasia, trap/treat/neuter/release). We compared mark-resight and distance sampling abundance estimates of free-roaming cats in an urban landscape, where limited public access to habitat frequently hinders the use of probabilistic sampling designs and associated sampling methodologies. We marked a subset of free-roaming cats (n = 52) with radio-collars in Caldwell, Texas to aid in obtaining our estimates. From road surveys (n = 20) conducted in August 2005, we found mark-resight estimates (N = 744, 95% CI 518-1,135) were significantly different (p = 0.008) to distance sampling estimates (N = 296, 95% CI 262-333). Study results suggest that distance sampling provides wildlife managers a viable alternative for estimating free-roaming cat populations in urban areas where minimal cost and training influence policy decisions regarding the implementation of monitoring and population control measures.