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Simple Summary: Herds of free-roaming, unowned horses can grow rapidly on rangelands with limited resources. Contraception can offer a humane, publicly acceptable method for slowing or stopping horse population growth and protecting the range. The best-tested and most widely used contraceptive for wild horses, porcine zona pellucida (PZP), a protein-based vaccine, has successfully stabilized or reduced free-roaming horse herds in different environments. While extensive research has shown that the PZP vaccine is safe, concerns still exist about its possible effects on the behavior and well-being of treated mares, and especially the survival of their offspring. Reporting the results of an eight-year study of PZP contraception in wild horses at two sites in the western USA, we show here that mares without foals improved the body condition faster than mares with foals. We also found that the foaling seasons of the PZP-treated herds were later in the year and more spread out. However, deaths of the foals born to PZP-treated mares through their second year of life were very rare and no more frequent than those of foals born to untreated mares. Thus, at our study sites, the timing of breeding was changed by PZP treatments, but we found no evidence that these changes were harmful either to the treated mares or their foals. 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. [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.

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]

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.

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]