Modeling white-tailed deer Odocoileus virginianus population control by contraception

Large populations of white-tailed deer Odocoileus virginianus present conservation problems in suburban landscapes because of limited population control options. We used the GAPPS II modeling system to simulate temporal effects of contraception on deer population control and the interaction between contraception and uncertain immigration rates. Contraception rates less than 50% of female deer curbed population growth with a long (30 year) planning horizon, but did not reduce the size of the population. A minimal contraception rate of 50% was necessary to reduce population size, but even with contraception rates > 50% a 5–10 year planning horizon was necessary to see significant population declines in a closed population. Variability among simulations with the same contraception rate was high and suggests difficulty in detecting population changes in the field. This difficulty could pose management problems because contraception is most economically applicable for smaller populations. For an open population, population size was a non-linear function of contraception and immigration rates. Contraception does not seem a viable option for an open population unless a landscape-level conservation strategy is implemented to control metapopulation growth.