Modeling the effect of sterilization rate on owned dog population size in central Italy.

A spreadsheet population dynamics model was constructed to evaluate the impact of female dog sterilization on the domestic dog population for the province of Teramo, Italy. Baseline owned dog population structure as well as the annual number of births, adoptions, abandonments, and purchases were estimated based on regional managed kennel data in addition to a telephone questionnaire administered to members of the local population. Age- and gender-dependent death rates were based on domestic dog life tables. The model predicts that at the current female dog sterilization rate of 30%, the owned dog population will most probably continue to increase. After 20 years, a mean annual increase of 2.6% (median: 2.5%, 95% CI: -3.2% to 8.8%) is projected assuming that the average age at sterilization is 3 years. A sterilization rate of at least 55% is estimated to be needed to halt population growth if the current age structure for female dog sterilization is maintained. However, if the province of Teramo were to focus on sterilizing female dogs less than 1 year of age, the required sterilization rate to arrest population growth could be reduced to as low as 26%.