Evaluation of euthanasia and trap–neuter–return (TNR) programs in managing free-roaming cat populations

Global estimates of the number of domestic cats (Felis catus) are >400million. Issues associated with freeroaming cats are of global importance because of animal-welfare and public-health concerns and impacts on native wildlife throughpredation, competition anddisease transmission. In theUnitedStates, proposedcontrol solutions formanagingurban free-roaming cat populations include euthanasia and trap–neuter–return (TNR) programs. We evaluated control methods using a demographic populationmodel for a 25-year period,with parameters estimated fromanunmanaged, free-roaming cat population inTexas.Wemodelledeuthanasia andTNRat 25%,50%and75%implementation rates anda50 : 50combination of euthanasia and TNR at 25%, 50%, 75% and 100% implementation rates for 0%, 25% and 50% maximum immigration rates. We compared final population size, total number of cats treated and treatment effort relative to population reduction. Population decreases were comparable among euthanasia, TNR and a 50 : 50 combination for all treatment rates when the immigration ratewas0%;however, theywere higher for euthanasia at 25%and50%maximumimmigration rates. Euthanasia required higher treatment effort than TNR. Our results indicate that immigration must be prevented and high (>50%) treatment rates implemented to reduce free-roaming cat populations.