Free-roaming cat populations must be managed for a variety of reasons, such asreducing predation on wildlife and mitigating nuisance behaviours. Thesepopulations can be controlled through trap-neuter-return (TNR) programs orculling, and the effectiveness of these programs is often measured usingchanges in the population size or number of sterilised cats. Culling andsterilisation impact cat population dynamics in different ways, consequently,the long-term impact of these methods will vary. For example, these differentmethods may impact the numbers of cat births, deaths, and immigrations andthese may have more long term influence overall than the obvious shorter termmanagement impact. This US study used population modelling to estimate thecumulative impact of different culling and TNR methods on a hypothetical catpopulation over a 10-year period.
Using a previously developed computer model, the population dynamics of thehypothetical population of cats was simulated under different controlscenarios. The population size was initially 50 cats, and the following sixmanagement scenarios were simulated for a 10-year period: no action, culling25% of cats every 6 mths,
culling 50% of cats every 6 mths, sterilising 25% of cats every 6 mths, orsterilising 75% of cats every 6 mths. The simulation was run 1000 times foreach scenario, and the average cat population and the cumulative number ofdeaths for each strategy was calculated. All kitten deaths and culled adultcats were considered preventable deaths, as they could have potentially beenreduced through population management.
The cumulative number of preventable deaths over 10 years was highest when nomanagement action was taken, as this method would allow populations toincrease to the point where kitten survival was impacted. The lowest number ofpreventable deaths occurred when the high-intensity (75%) sterilisationprogram was implemented, as it quickly suppressed reproduction. In conclusion,with sufficient intensity, TNR programs offer significant advantages in termsof minimising preventable deaths and reducing population size in cats.Thoughtful choice of management strategies can ensure that suffering andpreventable deaths are minimised in free-roaming cat populations.
Boone JD et al (2019) A long-term lens: Cumulative impacts
of free-roaming cat management strategy and intensity on
preventable cat mortalities. Frontiers in Veterinary Science 6:238.
S ource: RSPCA Science Update October
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