As human populations increase and urbanization expands, conflicts between humans and wildlife are growing exponentially. Traditional methods to resolve such conflicts generally focus on lethal management including shooting, trapping and toxicants. It is clear that integrated management practices offer the best chances of success, however, there are situations when the tools available are limited. For example, in some situations lethal methods may be logistically unfeasible, illegal, socially and/or politically unacceptable, or ineffective. In the late 20th century, researchers began exploring the possibility of mitigating conflicts by using fertility control to manage wildlife populations. Over the years, an array of methods have been developed and field tested for both wildlife and free-roaming feral populations of animals. Significant progress has been made in the development of both agents and delivery systems, as well as in modelling the impact of fertility control, alone or in conjunction with more traditional methods, to manage these populations. Some challenges remain, mainly related to feasibility, costs and sustainability that must be overcome to meet the demand by the public and wildlife managers for effective, alternative methods that can be incorporated into successful management practices. This symposium will feature a series of research and case studies on the use of fertility control methods to manage overabundant wildlife/free-roaming populations in a wide spectrum of contexts and species, highlight advantages and limitations of using fertility control to manage animal populations, and provide information on current research towards new tools for fertility control.
|Deer Population Demographic Impacts of Intensive Surgical Sterilization Treatments|
|Anthony J. DeNicola; Vickie L. DeNicola|
|Overabundant suburban deer (Odocoileus spp.) are a source of human-wildlife conflict in many communities throughout the United States. Deer-vehicle collisions, tick-borne pathogens, impacts on local vegetation, and other negative interactions are the typical reasons cited for initiating a deer management program. Social attitudes, legal constraints and perceived safety concerns lead many communities to examine nonlethal management options. Surgical sterilization is currently the only nonlethal method available to permanently sterilize females with a single treatment. There are limited data demonstrating methods and outcomes in high percentage (>90%) surgical sterilization programs; particularly impacts of immigration on non-isolated populations. We present data from six surgical sterilization sites with open populations (not fenced or island environments) in California, Maryland, Michigan, Ohio, Virginia, and New York, USA. From 2012 to 2020, we sterilized 493 deer via tubal ligation and ovariectomy. Annual or periodic population estimates were conducted using camera surveys, road-based distance sampling, and intensive field observations to assess population trends. We noted an average reduction in deer abundance of 25% from Year 1 to Year 2. Initial populations ranged from approximately 6 – 63 deer/km2 (14 – 169 deer/mi2). At research sites with 4 years of sterilization treatment (4 sites), we noted an average total reduction of 45%, resulting in an estimated 2 – 32 deer/km2 (6 – 86 deer/mi2) at each location. These projects clearly demonstrate that significant reductions in local deer densities using high percentage surgical sterilization programs can be achieved. Finally, we provide details on long-term program maintenance strategies using local volunteers.|
|Use of Fertility Control to Manage Urban Prairie Dog Populations|
|Dan Salkeld; Jackson Runte; Aaron Shiels; Douglas Eckery; Gary Witmer|
|Animal populations co-existing with urban human populations raise many issues, including conservation, public health, impacts upon habitats and property, and people connecting with nature. Black-tailed prairie dogs are a ‘keystone species’ for ecological health in the western US, but colonies can expand and over-graze, causing concerns for local land-owners. Lethal control is difficult, can be distressing to local stake-holders, and may not be effective if populations rebound rapidly or reinvade.
We investigated the potential of an immunocontraceptive – GonaCon – to humanely and sustainably manage prairie dog populations by reducing breeding success. We used three matched pairs of sites – one site where we vaccinated adult female prairie dogs with GonaCon, and one site where we administered a sham vaccine – in Fort Collins and Denver, Colorado. Visual measures of reproductive output (number of offspring emerging from adult female’s burrows) were significantly lower in Gonacon-treated sites.
|The Current Status and Future of Fertility Control Technologies to Manage Peri-Urban Kangaroo Populations in Eastern Australia|
|Lyn A. Hinds; Claire Wimpenny; Doug Eckery|
|Management of wildlife in peri-urban landscapes is essential for ecosystem function and to reduce human-wildlife conflict. Fertility control has high appeal for peri-urban sites where other methods such as annual shooting may be problematic. Several viable fertility control options, such as implants of GnRH agonists or progesterone, or immunocontraceptive vaccines, are currently available for Eastern Grey Kangaroos, Macropus giganteus. To apply these agents, individuals must be captured, a labour-intensive activity which limits their application to small numbers of animals and those in contained populations. Significant benefits would accrue if an efficient system for remote delivery of a long-lasting fertility control agent was developed. Our initial trials demonstrated that hand injection of the GnRH immunocontraceptive vaccine, GonaCon, induced high levels of infertility in >70% female Eastern Grey Kangaroos (n=16) for up to 10 years. Currently we are comparing efficacy of hand injection and dart delivery of GonaCon vaccine to adult female Eastern Grey Kangaroos. We are observing responses over time in individuals (n=142) and are comparing population growth and fecundity between treated (n=3) and untreated (n=7) sites. In the 3 years following GonaCon treatment, 14%, 0% and 6% of hand-injected kangaroos produced a young, while 21%, 8% and 9% of dart-delivered kangaroos produced a young. In the three years following placebo treatment, 90%, 89% and 86% of females produced a young. Fecundity has decreased to between 0% and 22% in treated populations whereas fecundity in untreated populations ranged from 53% to 88%. Results so far indicate that if long-term efficacy is achieved, dart delivery of GonaCon will be at least 50% more efficient than capture and injection by hand. This approach therefore could provide an efficient and more cost-effective option compared to currently available fertility control methods which require kangaroos to be captured for treatment.|
|BLM Wild Horse and Burro Fertility Management; Application and Research|
|The Bureau of Land Management (BLM) is a multiple use agency that manages the Public Lands for their health and diversity, and the enjoyment of current and future generations. Two of BLM’s management goals for wild horses and burros (WHB) are to protect and manage WHB as a component of public lands, and to maintain a thriving natural ecological balance and avoid rangeland deterioration. Balancing these goals requires keeping WHB herd sizes at appropriate management levels (AML), based on available resources and other multiple uses. With over 95,000 BLM-managed WHB living on-range, herd sizes are far larger than AML in most herd management areas (HMA) across the American west, and wild horse herds commonly grow at rates over 20% per year. BLM has used fertility control vaccines, sex ratio manipulations, and gelding to help in slowing or stabilizing WHB population growth. The effectiveness of existing vaccines has limited duration. Fertility control measures, alone, cannot bring overpopulated herd sizes down to AML in the time scale needed to protect rangeland resources. BLM supports development and testing of longer-lasting fertility control methods, including intrauterine devices (IUDs), mare sterilization, and new fertility control vaccines.|
|Current and Future Research Towards New Methods of Fertility Control for Wildlife|
|Douglas Eckery; Rick Mauldin; Giovanna Massei; Jason Bruemmer|
|The effective management of wildlife and pest species is becoming increasingly necessary throughout the world, and requires a variety of methods and approaches. The use of fertility control as a tool to aid in wildlife management strategies is considered to have numerous benefits and has attracted substantial attention. The greatest benefits from the use of wildlife fertility control will be realized when it is used in conjunction with other tools in integrated management strategies. In the United States, several fertility control products have been registered for use in wildlife, including two different contraceptive vaccines. Both vaccines have been shown to be effective in a number of species, and have also been used successfully for the management of isolated populations of deer, horses and goats. However, their use has also highlighted the need for products that cause long-term infertility or permanent sterility, and the need for more effective methods of delivery. The USDA APHIS WS National Wildlife Research Center, with key collaborators, is involved in a number of research areas aimed at developing new tools for fertility control for different species. One area of research is aimed at developing a vaccine for use in horses that targets ovarian growth factors. Studies to date suggest this new vaccine could offer long-term infertility from a single injection. Another area is aimed at the development of an oral/mucosal vaccine. Proof of concept research has been conducted and highlights the potential for this much needed method of delivery. RNA interference is a promising technology that is being investigated that has the potential to develop products that can cause permanent sterility and also be species-specific. The challenges associated with the use of fertility control are not only technical in nature, but also involve regulatory, social, political and cultural aspects.|
Organizers: Doug Eckery, USDA APHIS WS National Wildlife Research Center, Fort Collins, CO
Supported by: The Botstiber Institute for Wildlife Fertility Control, USDA APHIS WS National Wildlife Research Center