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Wildlife managers and the public have expressed considerable interest in the use of contraception to help manage the populations of wild horses and burros (Equus caballus and E. asinus). Field testing has shown that two preparations of the porcine zona pellucida (PZP) vaccine, a simple emulsion (ZonaStat-H) and PZP-22 (which supplements ZonaStat-H with a controlled-release component) effectively prevent pregnancy in individual mares and can substantially reduce population foaling rates. To determine whether some PZP preparations might have secondary effects that harm treated mares or their foals, we examined the effects of PZP-22 vaccinations and the follow-up boosters of either PZP-22 or ZonaStat-H on adult female body condition, foaling season, and foal mortality in two wild horse herds in the western USA, Cedar Mountains Herd Management Area, Utah (CM; 2008–2015), and Sand Wash Basin Herd Management Area, Colorado (SWB; 2008–2014). At both sites in every study year, summer body condition scores improved faster in mares without foals than mares with foals (p < 0.001; CM, n = 234; SWB, n = 172), but PZP treatments did not affect mare body condition apart from their contraceptive effects. Births to mares treated with PZP within the previous three years were delayed and spread out over the foaling season, but foal mortality rates through the first and second year were low, unrelated to date of birth, and virtually identical for the foals of PZP-treated and untreated mothers (all comparisons n.s.; CM, n = 775, SWB, n = 640). Thus, in these two populations, we found no evidence that changes in reproductive timing associated with PZP treatments were harmful to either mares or foals.

Simple Summary: Because the ethical foundation for the management of free-roaming horses and burros is very muddled, debates over approaches to their management, including fertility control, focus almost exclusively on practicality. In the U.S., this tendency is reinforced by the federal laws that govern public lands management, which center decision-making processes on calculations about how to divide yield among users. Inevitably, outside market forces bias these decisions towards overuse, which ultimately harms the land. In our view, the land and all its inhabitants, including free-roaming horses and burros, wildlife, and people, will only thrive if the pressures of commercial use are removed, and if management is guided by ethics of care, which have rich and diverse cultural origins. Application of care ethics will specifically provide more clarity to horse and burro management, including the selection of appropriate fertility control agents. To be effective and publicly acceptable, management of free-roaming horses and burros in the United States and elsewhere needs a consistent ethical framing of the animals and the land they occupy. In the U.S., the two laws that largely govern wild horse and burro management, the 1971 Wild Free-Roaming Horse and Burro Act and the 1976 Federal Land Policy and Management Act ("FLPMA"), rest on conflicting foundations, the former based on an ethic of care and the latter on largely utilitarian principles. These conflicts specifically fuel debates over the selection of appropriate fertility control agents for horse and burro management. Because land-use and management decisions are largely controlled by the FLPMA, and because the ethical treatment of animals is typically considered under conditions established by their use, both the larger debate about equids and land management and the specific debate about fertility control are dominated by cost/benefit calculations and avoid broader ethical considerations. In our view, the long-term health and ethical treatment of free-roaming horses and burros, the lands they occupy, and the wildlife and people they share it with will require the replacement of the resource-use model with a more holistic, care-based approach. [ABSTRACT FROM AUTHOR]

Wildlife managers and the public have expressed considerable interest in the use of contraception to help manage the populations of wild horses and burros ( Equus caballus and E. asinus ). Field testing has shown that two preparations of the porcine zona pellucida (PZP) vaccine, a simple emulsion (ZonaStat-H) and PZP-22 (which supplements ZonaStat-H with a controlled-release component) effectively prevent pregnancy in individual mares and can substantially reduce population foaling rates. To determine whether some PZP preparations might have secondary effects that harm treated mares or their foals, we examined the effects of PZP-22 vaccinations and the follow-up boosters of either PZP-22 or ZonaStat-H on adult female body condition, foaling season, and foal mortality in two wild horse herds in the western USA, Cedar Mountains Herd Management Area, Utah (CM; 2008-2015), and Sand Wash Basin Herd Management Area, Colorado (SWB; 2008-2014). At both sites in every study year, summer body condition scores improved faster in mares without foals than mares with foals ( p < 0.001; CM, n = 234; SWB, n = 172), but PZP treatments did not affect mare body condition apart from their contraceptive effects. Births to mares treated with PZP within the previous three years were delayed and spread out over the foaling season, but foal mortality rates through the first and second year were low, unrelated to date of birth, and virtually identical for the foals of PZP-treated and untreated mothers (all comparisons n.s.; CM, n = 775, SWB, n = 640). Thus, in these two populations, we found no evidence that changes in reproductive timing associated with PZP treatments were harmful to either mares or foals.

In a joint program, Innolytics and the USDA National Wildlife Research Center collaborated in the development of nicarbazin as an avian contraceptive, initially for resident Canada geese and subsequently for feral pigeons. Unfortunately, the introduction of the original goose product, OvoControl G, in 2005, was a commercial failure. Political and social barriers as well as goose reproductive biology effectively thwarted attempts to establish the new technology with any meaningful market success. The introduction of the pigeon contraceptive has been less difficult and the new technology continues to gather momentum. Nevertheless, given the focus on instant results and gratification, contraceptive technology for birds – which works over time – continues to be challenging, and broad market acceptance remains elusive. Especially for short-lived and rapidly reproducing species, however, the market continues to replace outdated or ineffective techniques with the safer and more effective contraceptive tools.

To be effective and publicly acceptable, management of free-roaming horses and burros in the United States and elsewhere needs a consistent ethical framing of the animals and the land they occupy. In the U.S., the two laws that largely govern wild horse and burro management, the 1971 Wild Free-Roaming Horse and Burro Act and the 1976 Federal Land Policy and Management Act (“FLPMA”), rest on conflicting foundations, the former based on an ethic of care and the latter on largely utilitarian principles. These conflicts specifically fuel debates over the selection of appropriate fertility control agents for horse and burro management. Because land-use and management decisions are largely controlled by the FLPMA, and because the ethical treatment of animals is typically considered under conditions established by their use, both the larger debate about equids and land management and the specific debate about fertility control are dominated by cost/benefit calculations and avoid broader ethical considerations. In our view, the long-term health and ethical treatment of free-roaming horses and burros, the lands they occupy, and the wildlife and people they share it with will require the replacement of the resource-use model with a more holistic, care-based approach.

Fox squirrels are an emerging urban, suburban, and agricultural vertebrate pest in California. They cause a diversity of damage to vegetation and property. Multiple introductions of fox squirrels into California have led to a rapid expansion of their range in the state. Fox squirrels at the University of California, Davis increased from none to an estimated 1,609 between 2001 and 2009. Damage due to the dense population of fox squirrels is increasing. There are several population control options available, but social considerations may limit the viable options to non-lethal methods. This paper provides an overview of the impacts of the introduced fox squirrel in California and on the University of California, Davis campus.

Tree squirrels (Sciurus spp.) are highly successful immigrants to urban and suburban areas in North America and Europe, causing both economic and ecological damage. Control of such invasive populations is challenging but of increasing importance to local managers. We studied an invasive population of fox squirrels (S. niger) and applied an immunocontraceptive vaccine in an experimental study of demographic control. Here we integrate our data into a simple stage-structured population model to simulate population reduction under 2 treatment levels (60 and 80% of females, respectively) for vaccines lasting from 1 to 5 years. Contraception can be an effective means of reducing fox squirrel populations if the vaccine is effective for ≥2 years or if ≥71% of the females are treated. Over a 15-year period, fewer individuals require treatment at a treatment rate of 0.8 versus 0.6 due to a declining population size. This study illustrates how a simple population model may guide local resource managers in the design of control strategies for invasive species.

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]

Tree squirrels (Sciurus spp.) are highly successful immigrants to urban and suburban areas in North America and Europe, causing both economic and ecological damage. Control of such invasive populations is challenging but of increasing importance to local managers. We studied an invasive population of fox squirrels (S. niger) and applied an immunocontraceptive vaccine in an experimental study of demographic control. Here we integrate our data into a simple stage-structured population model to simulate population reduction under 2 treatment levels (60 and 80% of females, respectively) for vaccines lasting from 1 to 5 years. Contraception can be an effective means of reducing fox squirrel populations if the vaccine is effective for ⩾2 years or if ⩾71% of the females are treated. Over a 15-year period, fewer individuals require treatment at a treatment rate of 0.8 versus 0.6 due to a declining population size. This study illustrates how a simple population model may guide local resource managers in the design of control strategies for invasive species. [ABSTRACT FROM AUTHOR]

Wildlife management actions can alter fundamental behaviors of individuals and groups, which may directly impact their life history parameters in unforeseen ways. This is especially true for highly social animals because changes in one individual's behavior can cascade throughout its social network. When resources to support populations of social animals are limited and populations become locally overabundant, managers are faced with the daunting challenge of decreasing population size without disrupting core behavioral processes. Increasingly, managers are turning to fertility control technologies to supplement culling in efforts to suppress population growth, but little is quantitatively known about how either of these management tools affects behavior. Gonadotropin releasing hormone (GnRH) is a small neuropeptide that performs an obligatory role in mammalian reproduction and has been formulated into the immunocontraceptive GonaCon-B™. We investigated the influences of this vaccine on behavior of feral horses (Equus caballus) at Theodore Roosevelt National Park, North Dakota, USA, for a year preceding and a year following nonlethal culling and GnRH-vaccine treatment. We observed horses during the breeding season and found only minimal differences in time budget behaviors of free-ranging female feral horses treated with GnRH and those treated with saline. The differences observed were consistent with the metabolic demands of pregnancy and lactation. We observed similar social behaviors between treatment groups, reflecting limited reproductive behavior among control females due to high rates of pregnancy and suppressed reproductive behavior among treated females due to GnRH-inhibited ovarian activity. In the treatment year, band stallion age was the only supported factor influencing herding behavior (P<0.001), harem-tending behavior (P<0.001), and agonistic behavior (P=0.02). There was no difference between the mean body condition of control females (4.9 (95% CI=4.7-5.1)) and treated females (4.8 (95% CI=4.7-4.9)). Band fidelity among all females increased 25.7% in the year following vaccination and culling, despite the social perturbation associated with removal of conspecifics. Herding behavior by stallions decreased 50.7% following treatment and culling (P<0.001), while harem-tending behavior increased 195.0% (P<0.001). The amount of available forage influenced harem-tending, reproductive, and agonistic behavior in the year following culling and treatment (P<0.04). These changes reflected the expected nexus between a species with polygynous social structure and strong group fidelity and the large instantaneous change in population density and demography coincident with culling. Behavioral responses to such perturbation may be synergistic in reducing grazing pressure by decreasing energetically expensive competitive behaviors, but further investigation is needed to explicitly test this hypothesis. [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]

Abstract: Feral horses on Shackleford Banks Island, North Carolina, are managed by the National Park Service in order to reduce their impact on the fragile barrier island ecosystem. Management techniques include removal of young horses and immunocontraception of many of the mares using Porcine Zona Pellucida immunocontraceptive. This immunocontraceptive reduces the number of horses that need to be physically removed from the island, but there is concern that the contraception may be influencing the social behavior of the contracepted mares. We investigated the effect of immunocontraception on harem stability by tracking the number of harem changes of each adult mare through the breeding season over two seasons. In both seasons the mares that had been treated with the immunocontraceptive changed harems significantly more than mares never treated (2007 P =0.037 and 2008 P =0.016) and visited significantly more harems (2007 P =0.021 and 2008 P =0.011). The number of years treated did not have a significant effect on the number of harem changes (2007 P =0.145 and 2008 P =0.848), nor did the number of years a mare had been off contraceptive once the contraceptive was discontinued (2007 P =0.443 and 2008 P =0.826). Additionally, there was no significant difference in harem changes between mares that were actively contracepted and mares that had been treated in the past but were not currently actively contracepted (2007 P =0.336 and 2008 P =0.533). These results indicate that the PZP immunocontraceptive has a significant effect on harem stability and that once a mare has been contracepted the behavioral effect of the contraceptive treatment may not be readily reversed. [ABSTRACT FROM AUTHOR]

Abstract: Managers concerned with shrinking habitats and limited resources for wildlife seek effective tools for limiting population growth in some species. Fertility control is one such tool, yet little is known about its impacts on the behavioral ecology of wild, free-roaming animals. We investigated influences of the immunocontraceptive porcine zona pellucida (PZP) on individual and social behavior in bands of feral horses (Equus caballus) in three discrete populations and used 14 hierarchical mixed effect models to gain insight into the influences of PZP treatment on feral horse behavior. A model of body condition was the strongest predictor of feeding, resting, maintenance, and social behaviors, with treated females allocating their time similarly to control females. Time spent feeding declined 11.4% from low condition to high condition females (F 1,154 =26.427, P <0.001) and was partially reciprocated by a 6.0% increase in resting (F 1,154 =7.629, P =0.006), 0.9% increase in maintenance (F 1,154 =7.028, P =0.009), and 1.8% increase in social behavior (F 1,154 =15.064, P <0.001). There was no difference detected in body condition of treated versus control females (F 1,154 =0.033, P =0.856), but females with a dependent foal had lower body condition than those without a foal (F 1,154 =4.512, P =0.038). Herding behavior was best explained by a model of treatment and the interaction of band fidelity and foal presence (AIC c weight=0.660) which estimated no difference in rate of herding behavior directed toward control versus treated females (F 1,102 =0.196, P =0.659), but resident females without a dependent foal were herded 50.9% more than resident females with a foal (F 3,102 =8.269, P <0.001). Treated females received 54.5% more reproductive behaviors from stallions than control mares (F 1,105 =5.155, P =0.025), with the model containing only treatment being the most-supported (AIC c weight=0.530). Treated and control females received harem-tending behaviors from stallions equally (F 1,105 =0.001, P =0.969) and agonistic behaviors from stallions equally (F 1,105 <0.001, P =0.986). Direct effects of PZP treatment on the behavior of feral horses appear to be limited primarily to reproductive behaviors and most other differences detected were attributed to the effects of body condition, band fidelity, or foal presence. PZP is a promising alternative to traditional hormone-based contraceptives and appears to contribute few short-term behavioral modifications in feral horses. [Copyright &y& Elsevier]