Search

ABSTRACT 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. © 2015 The Wildlife Society. [ABSTRACT FROM AUTHOR]

Anthropogenic stress on natural systems, particularly the fragmentation of landscapes and the extirpation of predators from food webs, has intensified the need to regulate abundance of wildlife populations with management. Controlling population growth using fertility control has been considered for almost four decades, but nearly all research has focused on understanding effects of fertility control agents on individual animals. Questions about the efficacy of fertility control as a way to control populations remain largely unanswered., Collateral consequences of contraception can produce unexpected changes in birth rates, survival, immigration and emigration that may reduce the effectiveness of regulating animal abundance. The magnitude and frequency of such effects vary with species-specific social and reproductive systems, as well as connectivity of populations. Developing models that incorporate static demographic parameters from populations not controlled by contraception may bias predictions of fertility control efficacy., Many population-level studies demonstrate that changes in survival and immigration induced by fertility control can compensate for the reduction in births caused by contraception. The most successful cases of regulating populations using fertility control come from applications of contraceptives to small, closed populations of gregarious and easily accessed species., Fertility control can result in artificial selection pressures on the population and may lead to long-term unintentional genetic consequences. The magnitude of such selection is dependent on individual heritability and behavioural traits, as well as environmental variation., Synthesis and applications. Understanding species' life-history strategies, biology, behavioural ecology and ecological context is critical to developing realistic expectations of regulating populations using fertility control. Before time, effort and funding are invested in wildlife contraception, managers may need to consider the possibility that many species and populations can compensate for reduction in fecundity, and this could minimize any reduction in population growth rate. [ABSTRACT FROM AUTHOR]

ABSTRACT Continued range expansion of introduced eastern fox squirrels ( Sciurus niger) in the western United States could lead to widespread damage to agricultural crops, facility infrastructures, and displacement of the native western gray squirrel ( S. griseus). Because traditional management alternatives may not be feasible in many areas, public interest in the use of immunocontraceptive to control local populations has increased. We evaluated the efficacy of GonaCon™ immunocontraceptive vaccine for controlling eastern fox squirrel reproduction in Davis, California. We administered GonaCon to 33 male and 26 female fox squirrels, and a control substance to 33 males and 24 females. We subsequently compared the reproductive status, health, and serum concentrations of testosterone and progesterone of our treated and control populations. In our treated population, we also measured serum concentrations of antibodies to gonadotropin-releasing hormone (GnRH). To determine potential side effects of the vaccine, we recorded body weight and body condition of all animals, examined injection sites during each recapture, and observed the treated squirrels in the field for signs of discomfort and impaired mobility. Over 17 months, none of the recaptured GonaCon-treated females ( n = 20) reproduced, compared to 12 of 15 control females. Treated males and females developed sufficient antibodies to GnRH to suppress reproduction, suggesting that GonaCon has the potential to be 100% effective in inhibiting reproduction in both sexes. We also observed a reduction in physical signs of reproductive activity for males ( P < 0.001) and in hormone levels of both females ( P < 0.001) and males ( P < 0.001). Control and GonaCon-treated animals did not differ in body weight but vaccinated squirrels had poorer body condition scores and exhibited severe injection site abscesses. The abscesses may have been caused by the GnRH conjugate used in GonaCon. In our study, GonaCon was effective in reducing eastern fox squirrel reproduction. Changes in the conjugate or its preparation may reduce the severity of associated injection site reactions. © 2013 The Wildlife Society [ABSTRACT FROM AUTHOR]