Utilization of matrix population models to assess a 3-year single treatment nonsurgical contraception program versus surgical sterilization in feral cat populations.

This study constructed matrix population models to explore feral cat population growth for a hypothetical population (a) in the absence of intervention; (b) with a traditional surgical sterilization-based trap, neuter, and return program; and (c) with a single treatment 3-year nonsurgical contraception program. Model outcomes indicated that cessation of population growth would require surgical sterilization for greater than 51% of adult and 51% of juvenile (<1 year) intact female cats annually, assuming an approximate 3-year mean life span. After the population stabilizes, this would equate to sterilizing approximately 14% of the total female population per year or having approximately 71% of the total female and 81% of the adult female population sterilized at all times. In the absence of juvenile sterilization, 91% of adult intact females would need to be sterilized annually to halt population growth. In comparison, with a 3-year nonsurgical contraception program, an annual contraception rate of 60% of female juvenile and adult intact cats would be required to halt population growth, assuming that treated cats were retrapped at the same rate after 3 years.