Behavioral effects of an immunocontraceptive vaccine on eastern fox squirrels.
Managing pest species in urban and suburban areas is challenging, and contraception may provide a socially acceptable and effective management option for many species. The immunocontraceptive vaccine, GonaCon, effectively inhibits reproduction in many species of wildlife, but the behavioral effects are not yet well understood. Contraceptive-induced changes in behavior could raise animal welfare concerns and alter survival and reproductive rates in populations. These vital rates frequently are incorporated in population models to predict the population-level efficacy of contraception. Thus, understanding the behavioral impacts of contraception is necessary to accurately predict population-level effectiveness of contraception and to protect animal welfare. We investigated the behavioral effects of GonaCon on eastern fox squirrels (Sciurus niger), a pest species that has invaded much of the western United States, caused widespread damages to human infrastructure, and threatened native western gray squirrels (S. griseus). We used field observations to measure time-activity budgets and dominance, open field trials to measure exploratory behavior, and mirror image stimulation to measure aggression because GonaCon could alter these behaviors. Contrary to our predictions, we failed to detect any significant effects of GonaCon on any of these behaviors. Our results, combined with a previous study finding that GonaCon is highly effective at inhibiting reproduction in fox squirrels, indicate that GonaCon may be a viable control method for fox squirrels and that behavioral changes affecting the demographic parameters are unlikely to undermine population models used to predict the effectiveness of GonaCon.