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Wildlife Damage Management Conferences -- Wildlife Damage Management, Internet Center Proceedings for

2005

Overview of Impacts of and Introduced Ungulates on the Environment in the Eastern United States and Caribbean

Martin Lowney USDA-APHIS-Wildlife Services

Paul Schoenfeld U.S. Naval Base Guantanamo Bay, FPO, AE

William Haglan US Department of Interior, FWS

Gary Witmer USDA-APHIS-Wildlife Services, [email protected]

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Lowney, Martin; Schoenfeld, Paul; Haglan, William; and Witmer, Gary, "Overview of Impacts of Feral and Introduced Ungulates on the Environment in the Eastern United States and Caribbean" (2005). Wildlife Damage Management Conferences -- Proceedings. 88. https://digitalcommons.unl.edu/icwdm_wdmconfproc/88

This Article is brought to you for free and open access by the Wildlife Damage Management, Internet Center for at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Wildlife Damage Management Conferences -- Proceedings by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. OVERVIEW OF IMPACTS OF FERAL AND INTRODUCED UNGULATES ON THE ENVIRONMENT IN THE EASTERN UNITED STATES AND CARIBBEAN

MARTIN S. LOWNEY, USDA, APHIS, Wildlife Services, Moseley, VI, USA PAUL SCHOENFELD, U.S. Naval Base Guantanamo Bay, FPO, AE WILLIAM HAGLAN, US Department of Interior, FWS, Chincoteague, VI, USA GARY W. WITMER, USDA, APHIS, Wildlife Services, National Wildlife Research Center, Fort Collins, CO, USA

Abstract: Non-native wild and feral ungulates have been introduced throughout the world for many centuries. Often the reasons for introductions were narrow in scope and benefits or the ungulates escaped or were released. Justifications for some introductions have included providing opportunity, meeting cultural and dietary needs of people, fund raising, and aesthetics. Evaluations about the impacts to the environment, native wildlife, , and people were most likely looked at in a narrow prism or not fully evaluated. Ungulates commonly introduced in the Eastern United States and Caribbean islands over the last 150 years included white-tailed deer, sika deer, hogs, , , and donkeys. Introductions have resulted in harm to endemic vegetation, competition with native herbivores for food, safety hazards to , disease threats to livestock and native wildlife, crop damage, and on eggs and young of native species. Some introductions provide significant positive economic benefits to local communities and present a unique set of resource and social challenges for the resource manager. Social and economic considerations may preclude removal as a management option. Once problems are recognized, management options can be assessed. However, the cost and effort of eradicating or suppressing non-native and feral ungulate populations can be daunting. Scarcity of funding can limit the scope and ability to remove enough of the to result in long-term benefits. Also, once substantial population reduction of undesirable animals is achieved, support for continued management may decline as recognition of the problem fades. An integration of control methods and some support from the local people are required to achieve removal of non-native and feral ungulates. Various challenges need to be addressed for control or eradication methods and strategies to be successful.

Key words: eradication, feral ungulates, hoofed animals, introduced wildlife, , wildlife management

Proceedings of the 11th Wildlife Damage Management Conference (D.L. Nolte, K.A. Fagerstone, Eds). 2005

INTRODUCTION and non-native ungulates include deer A feral is a formerly (Cervidae), goats (Capra hircus), (Sus domesticated species that has reverted to a scrofa), horses (Equus callabus), wild state (Van Vuren 1992). Non-native (Ovis aries), and many other species. Long ungulates are those that have become (2003) listed about 86 species of ungulates established outside their natural range. Feral that have been introduced to various parts of

64 the world. However, Teer (2003) reported (Moriarty 2004), non-native large that 124 species or “varieties” of ungulates introductions in North America have been introduced to Texas alone. Their (Teer 2003), and mammal introductions in populations can be established several ways (Parkes and Murphy 2003). (Long 2003). Feral ungulates can be intentionally introduced for agricultural Economic and Ecological Considerations purposes or for recreational hunting (De Vos In 1988, feral swine populations et al. 1956, Wood and Barrett 1979, Gipson were reported in 19 states, primarily in the et al. 1998, Martin 2005), for personal southeastern United States and California objectives (Miller 1993), or so that a supply (Mayer and Brisbin 1991), but Miller (1993) of is readily available (Mayer and reported that feral hogs were now found in Brisbin 1991, Van Vuren 1992). Some 23 states and their range was expanding. ungulates may escape from and Feral hogs have an omnivorous diet establish feral populations (Stegeman 1938, comprised of mostly material (grasses, De Vos et al. 1956). Some populations of forbs, fruit, nuts, tubers, seeds, and shoots), ungulates have been established for no but also a variety of invertebrates and known reason. Also, populations of non- vertebrates, including fawns, livestock, native ungulates may be allowed to persist rodents, frogs, and other wildlife (Peine and due to their aesthetic value, hunting, food, Farmer 1990, Seward et al. 2004). income, or prohibitive cost to eradicate. Feral swine activities may seriously The introduction of non-native or impact agricultural systems, especially crops feral ungulates to non-indigenous and livestock (Ensminger 1961, Donkin may result in economic or 1985, Stinger et al. 1982, Seward et al. ecological harm or threaten and 2004). Feral swine damage $800 million in animal health (Long 2003, Teer 2003). agricultural crops each year in the United Domestic or wild animal health may be States (Pimentel et al. 2002). Forty of 58 harmed by the introduction of non-native county agricultural commissioners in ungulates that may be carrying disease California reported $1.7 million in feral agents which may infect domestic or wild swine damage to agriculture (Frederick animals, and harm commerce. Non- 1998). In Australia, livestock predation by indigenous species in the U. S. cause major feral swine has been estimated at over $100 environmental damage and losses costing million in losses each year (Choquenot et al. more than $138 billion annually (Pimentel et 1996). al. 2002). In the U.S., about 42% of listed Where feral swine occur in sizeable threatened or endangered species are at risk densities they have been implicated in losses primarily due to non-indigenous species to native flora and fauna, soil erosion, (Pimentel et al. 2002). The International declines in water quality, reforestation Union for Nature included feral pigs, feral damage, and reduced biodiversity (Wood goats, and red deer (Cervus elaphus) on their and Barrett 1979, Witmer et al. 2003b., list of the “100 of the World’s Worst Engeman et al. 2003). Widely introduced, Invasive Alien Species” (Lowe et al. 2004). feral pigs have contributed to declines and The book edited by Pimental (2002) of numerous species on oceanic contains chapters on introductions in islands and can have pronounced negative Australia, New Zealand, the United ecological effects on mainland areas when Kingdom, and the United States. Other populations are high (Waithman et al. 1999). recent reviews cover deer introductions in Peine and Farmer (1990) summarized

65 ecological damage to Great Smoky and an additional 24 and 5 animals Mountain National Park as greater than a have been considered for listing (U.S. Navy 95% reduction in herbaceous understory in 1981). It has been estimated that the beech (Fagus grandifolia) forests, reduction eradication of feral goats on Isabela Island in mature and flowering non-woody plants, (Galapagos Islands) will cost about $8.5 changes in plant species composition, million and require about 6 years to predation on a potentially threatened complete (Galapagos Conservation Trust salamander and a snail, an estimated 80% website: www.gct.org/isabela1.html). In reduction in micro-invertebrates in the soil, Australia, feral goats cause an estimated $18 siltation and contamination of streams, and million dollars in agricultural crop losses predation on native grouse and turkey nests. each year, but also bring in about $4 million Soil erosion, accelerated with feral swine in revenues to those that harvest and sell rooting activities, resulted in leaching of feral meat (Parkes et al. 1996). minerals from the leaf litter and soil (Peine White-tailed deer (Odocoileus and Farmer 1990), sets back plant virginianus) and sika deer (Cervus nippon) succession, and exacerbates exotic plant have caused damage to plant communities, invasion (Mungall 2001). agricultural crops, and forest resources when Engeman et al. (2003) reported feral introduced to non-native environments hogs adversely affected basin marshes in (Long 2003). This damage has been most Florida. The area of one marsh damaged pronounced on islands. White-tailed deer (e.g., rooting and foraging) was valued have been introduced throughout the between $1.2 and $4.0 million dollars, based Caribbean islands from the United States, on amounts wetland regulators allow Mexico, and South America for hunting (De wetland permit applicants to spend in Vos et al. 1956). They were introduced to mitigation attempts. in the 1850’s from the southeastern Feral goats cause severe damage to United States (De Vos et al. 1956). Also, island natural resources (Van Vuren 1992, white-tailed deer from Florida were Keegan et al. 1994, Parkes et al. 1996). introduced onto Guantanamo Bay Naval Damage includes large scale alteration of Station for hunting about 1954 (Capt. plant communities, negative impacts on Dupree, U.S. Marine Corps, pers. commun.). insular endemic species of plants and Sika deer were introduced to Assateague animals, and damage to soils. The principle Island, Maryland in 1923. impact is damage to vegetation which results Feral horses and burros (Equus in alteration of the plant communities and ) have become established in many cascades into impacts on soils and animals parts of the world; in the U.S., they occur in that depend on unaltered plant communities several western states and on several barrier for habitat (Van Vuren and Coblentz 1987). islands along the east coast (Jenkins and Protection of insular ecosystems is probably Ashley 2003, Long 2003). They compete impossible without eradication of feral goats with livestock and native ungulates for (Vitousek 1988). Endemic biota on San forage and can damage habitats, especially Clemente Island, California has been at water sources (Jenkins and Ashley 2003, severely degraded by feral goats (Keegan et Long 2003). Feral horses on Assateague al. 1994). Four plants, two , and one Island, Maryland, were reported by National species endemic to San Clemente Park Service officials to be causing damage Island have been listed under the to natural grasses and dunes (Associated Endangered Species Act (U.S. Navy 1979) Press 2005). The damage the 160 feral

66 horses do to the is apparent. 2003a). Feral swine in Florida have been Feral horses grazed and trampled vegetation documented to have as many as 45 different on Cumberland Island National Seashore, parasites and infectious diseases (Forrester Georgia, and reduced plant biomass up to 1991). Feral swine in California were found 55% (Turner 1986). The impacts of grazing positive for brucellosis at 3 of 28 sites where on the salt marsh were stronger as above they were tested (Sweitzer et al. 1996). ground vegetation was reduced up to 98% Brucellosis is transmissible to man by feral horses (Turner 1986). Pimental et (Seigmond 1973). Other feral pigs in al. (2002) estimated that feral horses and California have tested positive for burros in the U.S. cause about $5 million in pseudorabies (Sweitzer et al. 1996). damages each year. Additionally, operation Ungulates and livestock may also serve as of the federal Wild and Burro reservoirs of bovine tuberculosis and Program (consisting mainly of the Adopt-a- leptospirosis, two other diseases Horse-or-Burro Program) costs about $20 transmissible to humans (Witmer et al. million per year (Jenkins and Ashley 2003). 2003a, 2004). The potential for exposure to While the eradication of non-native zoonotic disease in people from feral pigs is or feral ungulates may seem a logical of concern because hunters and others solution to the ecological and economic regularly handle and consume feral swine. problems that they cause, one must consider Sanitary handling and cooking of wild swine the unexpected ecological responses that can are important due to concern for result from such management actions. For trichinellosis, toxoplasmosis, and sylvatic example, invasive plants may gain a greater plague which has been found in feral pigs in foothold in plant communities once feral California (Sweitzer et al. 1996). sheep (Klinger et al. 2002) or feral goats The translocation of captive cervids (Bullock et al. 2002) are removed. In in the U.S. has facilitated the distribution of another example, Golden eagles (Aquila chronic wasting disease to several states chrysaetos) began using the Northern (Miller and Williams 2003). The potential Channel Islands of California, in part impact of this emerging disease on native because of the prey base that introduced ungulate populations has resulted in feral pigs provided. Unfortunately, with restrictions or bans in several states on the control of the feral pigs, the eagles have transport and keeping of captive deer and preyed more heavily on the endangered elk. (Urocyon littoralis)(Roemer and Donlan 2004). CASE HISTORIES

Human and Animal Health White-tailed Deer and Feral Goats at Feral swine are a reservoir of at least Guantanamo Bay, Cuba 30 significant viral and bacteriological The U.S. Naval Base Guantanamo diseases (Williams and Barker 2001) and Bay, Cuba (GTMO) occupies approximately there is a concern regarding the role feral 29,000 acres including 9,000 acres of open swine may have in an outbreak of a foreign water. The base is located in the animal disease (e.g., foot-and-mouth Guantanamo Province near the southeastern disease) (Witmer et al. 2003b). The highly tip of Cuba. The area is considered tropical infectious diseases pseudorabies and swine desert/dry forest habitat due to its location in brucellosis are considered threats to the the rain shadows of the Sierra Cristal and commercial pork industry (Witmer et al. Sierra Maestra Mountians. Average annual

67 rainfall is less than 20 in per year and canopy. The direct impacts from excessive precipitation normally occurs in heavy on native flora are somewhat downpours in two short “rain seasons”, obvious, but there are also impacts to coral generally once in May and again in October- reef habitats from accelerated rates of November. As such, the area supports some erosion and sedimentation into receiving very unique, rare, and endemic flora and waters when vegetated buffers are degraded fauna. A Rapid Ecological Assessment or completely denuded. (REA) of GTMO conducted by the Nature There are also indirect impacts on Conservancy in 1999 identified 70 plant native fauna as their habitats become species endemic to the Antilles including 51 degraded. For example, the goats and deer species endemic to Cuba and four endemic are competing for food with the endemic, to GTMO and the associated dry forest of federally-threatened Cuban ground iguana the Guantanamo Province (Roca and ( nubilus) (Roca and Sedaghatkish Sedaghatkish 1998). The REA further 1998). Wide-scale habitat defoliation has identified a large number of animal species resulted in iguanas moving over larger areas endemic to Cuba: 21 species of and in search of food and shelter. The increased amphibians, 8 species of birds, and 4 species movements through denuded habitats of endemic to the Caribbean. This subjected iguanas to higher levels of high rate of endemism is characteristic of mortality than what normally occurs when island biogeography and amplified at iguanas occupy a territory within adequate GTMO by the somewhat unique climate and habitat. In addition, dispersal has subjected associated ecotypes found here. juvenile iguanas to increased mortality while Unfortunately, the magnificent floral searching for adequate habitat in which to biodiversity of GTMO, that accounts for establish a home range. Iguana mortality 1.7% of the Caribbean flora, is currently factors include natural predation from under great stress because of over-grazing snakes and raptors, but also anthropogenic by populations of feral goats, introduced causes such as predation from feral white-tailed deer and high densities of the (Felis catus), feral dogs (Canis familiaris), native rodent, hutia (Capromys pilorides) and feral (Gallus gallus), vehicle (Areces-Mallea 2000). The overgrazing has strikes, and illegal collection for food or gone beyond the limits of self-sustainability economic gain. of most extant terrestrial ecosystems with In addition, excessive numbers of plant communities loosing their original goats and deer have presented other richness and density at an unprecedented problems such as aircraft and vehicle strike rate (Areces-Mallea 2000). hazards. There have been numerous The ecological impact of intensive collisions with vehicles, resulting in damage browsing and defoliation of this ecosystem to government and privately-owned from feral goats and introduced deer is vehicles. Residents have also complained of amplified when combined with excessive damage to the landscaping of their yards as herbivory from the overly abundant goats and deer ventured into residential population of the herbivorous hutia. While areas. habitat degradation from feral goats and deer While deer were brought to GTMO impacts vegetation from the forest floor to a for recreational hunting, at some point in the browse line at about 1.5-2 m, excessive mid- to late-1980s, recreational hunting was numbers of hutia have adverse impacts to all stopped on the base. Goats were initially vegetation, including cacti and the dry forest used as livestock. Privatization of the labor

68 force resulted in an influx of persons from success of the invasive species control other countries with little interest in raising operation is heavily dependent on funding, goats. Subsequently, the animals were requiring about $92,500 annually. These released or escaped from captivity. Because programs must be in continuous operation there are virtually no predators for these unless substituted with recreational hunting species at GTMO, goat and deer populations or the target invasive species will recover grew unchecked. and high damage levels will return. Non-native and feral ungulate Therefore, ongoing and continued support is control at GTMO began in 2001, targeting considered a management priority requiring the overly abundant goats and deer, but education and outreach efforts towards those included other invasive species (feral cats, who authorize and fund these programs. In feral dogs, feral chickens, pigeons (Columba some cases, research is conducted to support livia), and helmeted guinea fowl (Numida management decisions and operational meleagris) and management of high methods. densities of native hutia. Forsyth et al. There are many factors influencing (2000) argued the case for multiple decisions made relative to the control introduced herbivorous species management program at GTMO. One consistent problem to increase efficiency and effectiveness. at military facilities is the rapid turnover rate The base established a permanent Natural of personnel, including those in high-level Resources Manager position to manage decision-making capacities. As control these feral animals as part of a programs progress, the target species is no comprehensive Natural Resources longer perceived as a problem and when Conservation Program. Management efforts personnel transfer into a given facility, they resulted in significant reductions in invasive have little or no working knowledge of the species populations and acceptable densities history or accomplishments of the existing of native hutia. Between 2001-2004, about control program. Often, they perceive this 121 goats and 750 deer were removed from function as unnecessary in spite of GTMO. Both day and night shooting from educational and outreach attempts. The foot and vehicles were employed in the decision may also be influenced by local control effort. The subsequent eradication special interest groups opposed to of feral goats and substantial reduction of controlling animal populations, especially deer resulted in habitat recovery and when numbers have been reduced to where subsequent observations of larger numbers the population is not considered a problem. of species targeted for conservation such as In this case, low density and healthy iguanas, especially juvenile iguanas, and populations of deer, for example, occupying other smaller iguanid-type lizards of Cuba. recovered habitat can reach their full Although difficult and cost prohibitive to reproductive potential with irruptive growth quantify, these cursory observations were in the population. The population numbers also noted by several cooperating biologists quickly rebound to problematic levels and, from different agencies and organizations as is often the case, those responsible for who routinely visit GTMO on recurring curtailing control activities have since projects. transferred to a different facility. Continued support from officials in decision-making capacities is vital to successful wildlife damage management and invasive species control and eradication. The

69 Feral Horses and Sika Deer at arrival of Europeans two other ungulates, Chincoteague National Wildlife Refuge feral horses and sika deer, were introduced (NWR), Virginia to the islands. Over time, sika deer have Chincoteague NWR, located entirely colonized Assateague Islands. primarily on the Virginia portion of While popular folklore would like Assateague Island and including the Chincoteague “pony” to be descendants Chincoteague Island, consists of more than of survivors of shipwrecked Spanish 14,000 ac of beach, dunes, marsh, and galleon, more likely the horses are feral maritime forest. The refuge was established ancestors of stock grazed to avoid fencing in 1943 to provide habitat for migratory regulations and taxation. Early settlers birds. More than 320 species of birds are quickly recognized the abundant forage known to occur on the refuge. The refuge resources of Virginia’s barrier islands and has been designated a Globally Important stocked the islands with horses, (Bos Area, is part of the Western taurus), and sheep. The islands required no Hemisphere Shorebird Reserve Network and fencing and their remoteness precluded any designated as one of the top ten birding supervision by the tax assessor. In 1671, Hotspots by the National Audubon Society Colonel Daniel Jenifer attained a land grant (see Refuge website: www.fws.gov/ on Assateague Island allowing him to graze northeast/chinco). Refuge management his livestock and avoid the mainland fencing programs restore threatened and endangered ordinance and the mainland tax assessor. In species such as the Delmarva Peninsula fox 1808, George Washington Parke Custis, squirrel (Sciurus niger cinereus), the bald step-grandson of George Washington, eagle (Haliaeetus leucocephalus) and the advocated the value of raising sheep on the piping plover (Charadrius melodus). More islands. Penning began for livestock owners than 2,600 ac of man-made marshes, or to claim, brand, break, and harness their moist soil management units, are managed loose herds. In 1835, Thompson Holmes for wintering waterfowl and shorebirds described the annual horse penning on during migration. With about 1.4 million Chincoteague Island and indicated the visits a year, Chincoteague NWR is one of practice had occurred at least 30 years prior. the most visited refuges in the nation. A fence along the Virginia/Maryland Assateague Island is a barrier island State line (the northern refuge boundary) extending north and south with Atlantic separates the island's feral horses into two Ocean to the east and the mainland to the herds. The National Park Service (NPS), west. The Island has beaches, dunes, grassy Assateague Island National Seashore, areas, shrub areas, marshes, and forests manages the Maryland herd. The Virginia consisting of loblolly pine (Pinus taeda) and herd is owned by the Chincoteague some hardwood species. The refuge also Volunteer Fire Company and is grazed in contains manmade freshwater areas that two pastures. Horses have been allowed to cover 2,623 ac and provide submergent and roam freely on the refuge, but resource emergent wetland vegetation for wildlife. damage to the dune system and conflicts Salt marsh areas are found between with refuge visitors and vehicles resulted in Assateague Island and Chincoteague Island confinement to pastures. Chincoteague and the mainland. NWR horse numbers are maintained at 150 White-tailed deer are the only native adults; foals are sold each year during ungulate found on Chincoteague NWR and “pony” penning. The Maryland herd is the rest of Assateague Island. Since the regulated by immuno-contraceptives with a

70 population objective of 100-125 horses. In For effective control or eradication, the use 1947, Marguerite Henry published "Misty of of multiple methods is usually required Chincoteague," the story that immortalized (Schuyler et al. 2002, Butchko et al. 2003). Chincoteague “ponies” and made the horses Methods currently available to remove non- internationally famous. “Pony” penning native ungulates were summarized by Van occurs in July and 40,000 to 50,000 visitors Vuren (1992), Barrett and Biringham are attracted to Chincoteague Island to view (1994), Choquenot et al. (1996), Parkes et the penning and foal . “Pony el. (1996) and McCann et al. (2004). Of Auction” revenues provide revenue for the course, the costs and effectiveness vary fire company. considerably among the methods Sika deer, native to eastern Asia, (Choquenot et al. 1996). The application of have been introduced to many parts of the benefit-cost analyses can help in deciding on world (Long 2003). In the early 1900’s, which method(s) to use and whether or not Clemment Henry of Cambridge, Maryland, control is warranted (Schwiff 2004). obtained a small herd of sika deer from an Research continues to improve existing unknown source. In 1916, he released a methods and to develop new methods. number of deer on James Island that eventually became the source of sika deer on Monitoring and Surveillance the Maryland mainland. Dr. Charles Law of Monitoring and surveillance are Berlin, Maryland, purchased a number of important components of an effective non- deer, most likely from Mr. Henry. Those native ungulate management program deer were either sold to an individual who (Butchko et al. 2003, Peine and Farmer later released them on Assateague Island or 1990, Choquenot et al. 1996, Parkes et al. were obtained by the Boy Scouts who 1996). Monitoring and surveillance are operated a petting zoo at Ocean , necessary to establish locations used by Maryland, and later released them on target species, develop baseline populations Assateague Island. Regardless, sika deer for target species, and measure efficacy of found the island to their liking and have removal efforts of non-native ungulate. been present since the early 1920’s. Sika A conundrum of monitoring and deer compete better than white-tailed deer surveillance is detecting remnant survivors for food resources on Assateague Island, after control or newly-arrived individuals. resulting in an apparent decline in native Survivors tend to be low in abundance, deer (Keiper 1985). Hunting programs for dispersed, and wary. Several methods have Sika deer occur on Chincoteague NWR and evolved to detect remnant populations on NPS lands. Approximately 400-500 deer including aerial surveys by helicopter, use of are taken yearly on Assateague Island. The detection dogs, snow or sand tracking, sika deer population is managed through cameras at bait or water stations, systematic hunting to prevent damage to native flora sweeps of areas, and “Judas” goats. Judas and to limit competition for food resources goats are animals that are captured and fit with native wildlife. with radio collars. The collared animal is released and allowed to return to other METHODS OF CONTROL remnant individuals. This method works Methods of control available to well with social ungulates (Taylor and remove or eradicate non-native and feral Katahira 1988). ungulates include monitoring and surveillance methods and control methods. Sterilization of Feral Horses

71 Sterilization has been used as a baiting, and good trap design (Sweitzer et al. means of controlling populations 1996, McCann et al. 2004). Although feral for a number of years (Kirkpatrick et al. pigs will eat a wide variety of baits, they 1997). Sterilizing males is not effective for tend to prefer fermented corn or corn-based many ungulate species because of the commercial feed (McCann et al. 2004). polygamous mating system of sheep, goats, Feral pigs may be effectively snared deer, and hogs. However, sterilization can in trails (Richardson et al. 1997), especially be effective for horses because the fertility when snares are placed in trails on the way of an entire herd could be controlled through to bait piles. All hunting or other human the treatment of a single stallion (Warren et disturbance should cease once trapping al. 1997). Disadvantages of sterilization begins because increased human activity include immobilization cost, surgery often results in feral pigs moving to other requirements, and dangerous, hard work areas (Richardson et al. 1997). Deer are also required (Warren et al. 1997). Of course, an susceptible to being snared along trails. additional requirement is the sterilization of Rocket nets or drop nets are two each successive stallion that takes over the types of nets regularly used to capture deer harem (Slade and Godfrey 1982). and other ungulates (Connor et al. 1987, Sterilization would be less effective in herds Schemnitz 1994). Ungulates are vulnerable having sexual mature subordinate stallions to being captured by nets propelled or or a high degree of movement by mares dropped over feeding individuals. between harems (Warren et al. 1997). Ungulates can be effectively baited in with high-energy foods, such as corn, during the Trapping winter months when natural foods are Trapping has removed tens of scarce. Feral pigs are also vulnerable to this thousands of feral goats and sheep from technique. islands (Van Vuren 1992). Traps have also been used extensively for feral pigs, deer Shooting from the Ground and horses. Trapping can be logistically Shooting from the ground has proven difficult and will not lead to eradication to be a very effective technique (Van Vuren since some ungulates will be “trap-shy” and 1992, McCann et al. 2004). Biologists and elude capture (Van Vuren 1992). Both technicians working in teams can kill large single-animal and multiple-capture traps numbers of non-native or feral ungulates have been used and many designs are quickly and economically (Van Vuren available (Barrett and Birmingham 1994, 1992). Most successful goat and sheep Schemnitz 1994, Choquenot et al. 1996, eradication programs have been achieved by Parkes et el. 1996). The use of radio- shooting from the ground. Shooting can be transmitters on remote traps can improve conducted during day or night hours, and efficiency by allowing personnel to shooting over bait often increases determine, from a distance, that a trap has effectiveness. been triggered (McCann et al. 2004). Shooting is one of the more effective Trapping wild pigs is labor intensive. methods for reducing feral swine Cage trapping was the most effective populations (Peine and Farmer 1990). method to remove feral pigs and accounted Shooting pigs from the ground may be more for 75-80% of the pigs killed each year effective with the use of dogs, especially (Richardson et al. 1997). Trapping success when pigs are at low densities (McCann et may be contingent on pre-baiting, free- al. 2004). Public hunting has also been

72 used, although with only limited effectiveness of ungulate fencing. Horses, effectiveness, to control goats, and other ungulates can be rounded populations (Choquenot et al. 1996, up---a process sometimes called mustering-- Richardson et al. 1997). - into fenced areas, using helicopters or by The cost to eradicate deer by horseback (Parkes et al. 1996, Jenkins and shooting ranges from $300-$963 per animal Ashley 2003). (Martin 2005, Butchko et al. 2003). While public hunting has been ineffective at Recent Technological Advances eradicating deer, it has been effective at There have been technological controlling deer populations when hunters advances in equipment that are useful in are given adequate access to the area ungulate control and eradication. The use of (Vercauteren and Hygnstrom 2000). The forward-looking infrared (FLIR) thermal use of dogs to locate deer, and large imagers, night vision goggles, and numbers of people to drive deer from dense suppressed rifles are examples of vegetation, can aid in deer removal efforts technological advances that improve (Butchko et al. 2003). efficacy of ungulate removal programs. Belant and Seamans (2000) reported that Shooting from the Air FLIR detected more deer than spotlights and Shooting from helicopters is an night vision goggles (825 versus 716 deer). extremely effective and rapid method of In field tests conducted in Pennsylvania, population control of large animals (Baker FLIR detected up to 70% more deer in dense and Reeser 1972). However, it is very vegetation than spotlights (J. Suckow, pers. expensive and animals may learn to comm.). FLIR units can also be used from recognize the sound of the helicopter and helicopters (McCann et al. 2004). hide (McCann et al. 2004). Helicopters can Suppressors reduce the report of the be a key component to removal or rifle when a bullet is discharged. The eradication of deer or other ungulates reduction in report appears to reduce the (Butchko et al. 2003). Helicopters are also likelihood of deer fleeing. The reduced valuable for transporting equipment and noise is alsp beneficial when conducting traps, getting personnel into remote operations near inhabited areas. Suppressors locations, and for surveying areas for are regulated by the Bureau of Alcohol, ungulates (McCann et al. 2004). Tobacco, and Firearms and their availability is greatly restricted by statute. State and Fencing federal wildlife agencies are able to acquire Fencing can be an important necessary federal permits to use suppressors. component of control or eradication States may also have restrictive regulatory programs (McCann et al. 2004). Materials requirements on the use of suppressors. and installation, however, are very expensive and regular maintenance is Research on Methods Development required. Fencing may be used to partition Much research has been underway the island into smaller parcels to facilitate on fertility control of wildlife (e.g., eradication and to keep animals from Kirkpatrick et al. 1997). The issues and returned to an area once it is cleared of challenges of this method were reviewed by ungulates (Butchko et al. 2003, Van Vuren Fagerstone et al. (2002). Research has 1992). VerCauteren et al. (IN PRESS) identified several materials that could reviewed the many types, costs, and effectively sterilize non-native and feral

73 ungulates (Miller et al. 2004). Efficient 2002). Fertility control research on deer delivery methods remain a major challenge continues (Miller et al. 2004). with this method. Some novel approaches to non- Turner and Turner (1991) reported native and feral ungulate control and 29 percent fertility in treated feral horse eradication that are being investigated in herds compared to 45% fertility in control other countries, but not in the U.S., include herds when stallions were administered a broad-casting of toxic baits (Forsyth and microencapsulated form of testosterone Parkes 1995, Lapidge et al. 2004 ), use of propionate (MTP). Contraception would toxic pastes on foliage (Veltman and Parkes require annual treatments and would be less 2002), biological control via disease effective in herds having sexual mature transmission (Choquenot et al. 1996, Pech subordinate stallions or a high degree of 2000), and carnivore introduction (Parkes et movement by mares between harems al. 1996). Each of these approaches is not (Warren et al. 1997). Immuno- without serious disadvantages, including contraceptives have been used on wild non-target hazards, and can only be used horses (mares) to block ovulation for up to 3 under very unique or specific circumstances years. The vaccine (porcine zona pellucida) (Choquenot et al. 1996). was delivered remotely via darts, however, a booster shot was required to extend DISCUSSION AND MANAGEMENT contraception a second year (Kirkpatrick et IMPLICATIONS al. 1997). Improvements in fertility control Wildlife managers need to consider for horses have been made (Killian et al. many types of information in the 2004). Fertility control research is also management of non-native and feral underway on feral swine (Killian et al. ungulates. There are at least four important 2003). questions that need to be answered prior to Immuno-contraception used alone undertaking feral ungulate management for will not eradicate a population of non-native the project to succeed. These questions are deer over time because it is virtually 1) is eradication possible or should long- impossible to treat all, or even the vast term control be implemented? 2) is there majority, of the deer. The cost to contracept some support for eradication or control from deer is about $3,000 per animal (Martin local people? 3) do decision makers support 2005). Fertility control would, at least funding for eradication or control? and 4) theoretically, reduce habitat damage over the what are the economics of eradicating or long period term by preventing population controlling the ungulates? growth via mortality exceeding reproduction Is eradication possible or should and survival. Because of the relatively long control be implemented? Bomford and life span of most ungulates, however, the O’Brien (1995) identified six criteria, three damage may continue for many years or criteria that were critical, for eradication to even decades even though many animals are be successful. The three critical criteria that sterile. In one situation where immuno- must be met in the affirmative for contraception was used with a confined herd eradication to be successful were 1) the rate of wild deer, the population continued to of removal exceeds the rate of population increase in abundance even though deer increase for all population densities, 2) continued to be killed by vehicles and male immigration is prevented, and 3) all deer dispersed from their natal area (Naugle reproductive animals must be at risk for removal. The other three criteria that are

74 desirable for eradication to be successful are The support of decision-makers to 4) animals must be detected at low densities, provide funding for eradication or control is 5) discounted benefit-cost analysis favors required when government agencies are eradication over control, and 6) a suitable involved. Decision-makers could include socio-political environment exists. land managers, political appointees or We analyzed management options leaders, or advocacy groups. This support (eradication or control) for feral ungulates at may change over time for several reasons. GTMO and Chincoteague NWR using Support may be high initially when the non- analyses described by Bomford and O’Brien native or feral ungulate problem is most (1995). The analyses concluded that at acute. However, as ungulates are removed GTMO eradication of feral goats was from the environment and the level of achievable whereas eradication of deer was damage declines, decision-makers may be less clear because we were unable to say drawn to other pressing issues. A with certainty that immigration was continuous education effort is required to prevented (Table 1). For Chincoteague keep decision-makers, stakeholders, and the NWR, we concluded that the management public informed of the need to manage the of feral horses was preferred to eradication ungulates. due to benefit-cost analysis favoring Do the economics of non-native or management (Table 1). The initial analysis feral ungulates favor eradication or control? of management of sika deer appeared to Sometimes these ungulates generate benefits favor eradication, however, additional that are unusually large or affect a small benefit-cost analysis and socio-political local economy at times of the year when environmental factors need further other economic activity is low. Two exploration (Table 1). examples of benefits that require careful Support of local people for analysis prior to implementing a non-native eradication or control is necessary to garner ungulate management action would be the cooperation from landowners, advocacy feral horses and introduced sika deer on groups, government agencies, and political Chincoteague NWR. The Town of leaders. The level of support for Chincoteague, Virginia, receives nearly $32 management actions should exceed 50% of million dollars in annual non-consumptive the public. Realistically, the level of support use benefits from Chincoteague NWR will rarely exceed 85% of the public since (Caudill and Henderson 2003). Of these about 3% of the public has animal rights benefits, about $7.5 million are from bird values and 12% of the public has animal watching (Lowney et al. 2005). The welfare values (Duda et al. 1998a, 1998b). remaining $24 million in economic benefits While citizens with animal rights and animal are derived from the public using the beach welfare values may not support an (2/3 of visitors) and activities associated eradication or control action, they may with watching the feral horses as well as the remain neutral if they feel the action is annual “pony” swim and auction. We necessary and other reasonable means to estimate that the economic benefit resolve the human-animal conflict have been associated with the feral horses may be as tried. The cooperation of landowners and large as $8 million dollars, thus their the public is also essential so that access to management may be a more desirable all, or at least most, occupied areas can be management action than eradication (Table had for control operations. 1).

75

Table 1. Analysis of criteria to determine whether eradication or control of non-native and feral ungulates are appropriate management actions at Guantanamo Bay Naval Station, Cuba, and Chincoteague National Wildlife Refuge, Virginia. Analyses follow criteria established by Bomford and O’Brien (1995). Criteria Guantanamo Bay Chincoteague White-tailed Goats deer Horses Sika deer Rate of removal exceeds rate of Yes Yes Yes Yes increase Immigration is prevented Yes ? Yes Yes All reproductive animals at risk Yes Yes Yes Yes Animals can be detected at low Yes Yes Yes Yes? densities Benefit-cost analyses favors Yes Yes? No Yes? eradication over control Suitable socio-political Yes Yes No No environment

Sika deer are hunted by about 380 people on Additional challenges include adequate Chincoteague NWR each year during monitoring of ungulate populations to December and January. Hunting sika deer measure progress, maintaining support of creates a $27,200 economic benefit for the decision-makers who must approve funding, Town of Chincoteague during winter adequate funding to use costly control months when other tourism activities are methodologies and to pay salary costs, and low (Caudill and Henderson 2003). Sika overcoming political obstacles from diverse deer hunting provides a very small benefit advocacy groups that benefit from, or (0.07 %) of the total $40.4 million dollar otherwise support, non-native ungulates. benefit that the refuge provides to the local economy. This small economic benefit is LITERATURE CITED important to the local economy because of ARECES-MALLEA, A.E. 2000. Assessment of the time of year the benefit is accrued. This herbivore damage in plant communities small benefit would need to be weighed at U.S. Naval Station Guantanamo Bay, against ecological costs and socio-political Cuba. Unpublished Report. The New variables to determine the appropriate York Botanical Garden, Bronx, NY, USA. management action (Table 1). ASSOCIATED PRESS. 2005. Park Service may In conclusion, various challenges sell off some Assateague horses. need to be addressed for control methods to Richmond Times Dispatch, Richmond, be successful. Adequate resources and VA, USA. March 21, 2005. methods must be available to reduce the BAKER, J.K., AND D.W. REESER. 1972. Goat numbers of, or eliminate, the problem management problems in ungulates. This includes adequate Volcanoes National Park. Natural population monitoring, use of advanced Resource Report No. 2. USDI National technology, aerial operations, various traps, Park Service, Hawaii Volcanoes special shooting equipment, and highly National Park, HI, USA. skilled and dedicated wildlife specialists.

76 BARRETT, R., AND G. BIRMINGHAM. 1994. DONKIN, R.A. 1985. The peccary – with Wild pigs. Pages D-65 – D-70 in S. observations on the introduction of pigs Hygnstrom, R. Timm, and G. Larson, to the New World. Transaction of the editors. Prevention and control of American Philosophical Society 75:1- wildlife damage. University of 152 Nebraska Cooperative Extension DUDA, M.D., S.J. BISSELL, AND K.C. YOUNG. Service, Lincoln, NE, USA. 1998a. Consumptive wildlife-related BELANT, J.L., AND T.W. SEAMANS. 2000. activities. Pages 247 – 282 in Wildlife Comparison of 3 devices to observe and the American mind. Responsive white-tailed deer at night. Wildlife management. Harrisonburg, VI, USA. Society Bulletin 28:154-158 _____, _____, AND _____. 1998b. Animal BOMFORD, M., AND P. O’BRIEN. 1995. rights, animal welfare, and use of Eradication or control for vertebrate animals. Pages 285 – 293 in Wildlife pests. Wildlife Society Bulletin and the American mind. Responsive 23:249-255. management. Harrisonburg, VI, USA. BULLOCK, D., S. NORTH, M. DULLOO, AND M. ENGEMAN, R.M., H.T. SMITH, R.G. SEVERSON, THORSEN. 2002. The impact of M.A.M. SEVERSON, S.A. SHWIFF, B. and goat eradication on the ecology of CONSTANTIN, AND D. GRIFFIN. 2003. Round Island, . Pages 53-63 Amount and economic valuation of feral in C. Veitch and M. Clout, editors. hog damage to a unique basin marsh Turning the tide: The eradication of wetland in Florida. Florida Park Service invasive species. Invasive Species “Partnership” Technical Report. Florida Specialist Group, International Union Department of Recreation and Parks, for the Conservation of Nature, Gland, Tallahassee, FL, USA. Switzerland. ENSMINGER, M.E. 1961. Swine science. The BUTCHKO, P.H., A.G. DUFFINEY, JR., AND A.J. Interstate Printers and Publishers, MONTONEY. 2003. Eradication of a Danville, IL, USA. bovine tuberculosis-positive captive FAGERSTONE, K., M. COFFEY, P. CURTIS, R. cervid herd in northeast Michigan. DOLBEER, G. KILLIAN, L. MILLER, AND Proceedings of the Eastern Wildlife L. WILMOT. 2002. Wildlife fertility Damage Conference 10:408-413. control. Wildlife Society Technical CAUDILL, J., AND E. HENDERSON. 2003. Review 02-2. The Wildlife Society, Banking on nature 2002: The economic Bethesda, MD, USA. benefits to local communities of national FORRESTER, D. 1991. Parasites and diseases of wildlife refuge visitation. U.S. Fish and wild mammals in Florida. University of Wildlife Service. Washington, D.C., Florida Press, Gainesville, FL, USA. USA. FORSYTH, D., AND J. PARKES. 1995. Suitability CHOQUENOT, D., J. MCILROY, AND T. KORN. of aerially sown artificial baits as a 1996. Managing vertebrate pests: Feral technique for poisoning feral goats. pigs. Australian Government Publishing New Zealand Journal of Ecology 19:73- Service, Canberra, Australia. 76. CONNER, M.C., E.C. SOUTIERE, AND R.A. _____, _____, AND G. HICKLING. 2000. A case LANCIA. 1987. Drop-netting deer: for multi-species management of Costs and incidence of capture sympatric herbivore pest impacts in the myopathy. Wildlife Society Bulletin central Southern Alps, New Zealand. 15:434-438 New Zealand Journal of Ecology 24:97- DE VOS, A., R.H. MANVILLE, AND R.G. VAN 103. GELDER. 1956. Introduced mammals FREDERICK, J.M. 1998. Overview of wild pig and their influence on native biota. damage in California. Proceedings of Zoologica 41:163-194 the Vertebrate Pest Conference 18:82- 86.

77 GIPSON, P.S., B. HLAVACHICK, AND T. BERGER. Some practical tools in the design of 1998. Range expansion of wild hogs target-specific feral pig baits and baiting across the central United States. procedures. Proceedings of the Wildlife Society Bulletin 26:279-286. Vertebrate Pest Conference 21:317-322. JENKINS, S., AND M. ASHLEY. 2003. . LONG, J. 2003. Introduced mammals of the Pages 1148-1163 in G. Feldhamer, B. world. CSIRO Publishing, Thompson, and J. Chapman, editors. Collingwood, Victoria, Australia. Wild mammals of North America. The LOWNEY, M.S., W. SERVOSS, J.S. CROMWELL, John Hopkins University Press, AND D. REINHOLD. 2005. Management Baltimore, MD, USA. of predation losses to native bird KEEGAN , D., B. COBLENTZ, AND C. WINCHELL. populations on barrier and Chesapeake 1994. eradication on San Bay islands and coastal areas of the Clemente Island, California. Wildlife Commonwealth of Virginia. Society Bulletin 22:56-61. Environmental Assessment. USDA, KEIPER, R.R. 1985. Are sika deer responsible for APHIS Wildlife Services, Moseley, VI, the decline in white-tailed deer on USA. Assateague Island, Maryland? Wildlife MARTIN, G. 2005. Park Service wants to Society Bulletin 13:144-146. eliminate exotic deer at Point Reyes. KILLIAN, G., L. MILLER, J. RHYAN, T. DEES, D. San Francisco Chronicle, San Francisco, PERRY, AND H. DOTEN. 2003. California, USA. February 4, 2005. Evaluation of GNRH contraceptive in MAYER, J.J., AND I.L. BRISBIN. 1991. Wild pigs feral swine in Florida. Proceedings of in the United States. University of the Wildlife Damage Management Georgia Press, Athens, GA, USA. Conference 10:128-133. MCCANN, B., K. RYAN, AND D. GARCELON. _____, _____, N. DIEHL, J. RHYAN, AND D. 2004. Techniques and approaches for THAIN. 2004. Evaluation of three the removal of feral pigs from island and contraceptive approaches for population mainland ecosystems. Proceedings of control of wild horses. Proceedings of the Vertebrate Pest Conference 21:42- the Vertebrate Pest Conference 21:263- 46. 268. MILLER, J.E. 1993. A national perspective on KIRKPATRICK, J.F., J.W. TURNER, AND I.K.M. feral swine. Pages 9-16 in C.W. LIU. 1997. Contraception of wild and Hanselka and J.F. Cadenehead, editors. feral equids. Pages 161-169 in Feral swine: A compendium for Contraception in wildlife management. resource managers. Texas Agricultural Technical Bulletin 1853. T. Kreeger, Extension Service, Corpus Christi, TX, Technical Coordinator. USDA, APHIS, USA. WS National Wildlife Research Center, MILLER, L., J. RHYAN, AND G. KILLIAN. 2004. Fort Collins, CO, USA. GonaCon, a versatile GnRH KLINGER, R., P. SCHUYLER, AND J. STERNER. contraceptive for a large variety of pest 2002. The response of herbaceous animal problems. Proceedings of the vegetation and endemic plant species to Vertebrate Pest Conference. 21:269-273. the removal of feral sheep from Santa MILLER, M., AND B. WILLIAMS. 2003. Chronic Cruz Island, California. Pages 141-154 wasting disease of cervids: Implications in C. Veitch and M. Clout, editors. for wildlife management. Proceedings Turning the tide: The eradication of of the Wildlife Damage Management invasive species. Invasive Species Conference 10:306-309. Specialist Group, International Union MORIARTY, A. 2004. The liberation, for the Conservation of Nature, Gland, distribution, abundance and Switzerland. management of wild deer in Australia. LAPIDGE, S., B. COWLED, AND M. SMITH. 2004. Wildlife Research 31:291-299. Ecology, genetics, and socio-biology:

78 MUNGALL, E.C. 2001. Exotics. Pages 736-764 conservation: The case history of the in S. Demarais and P. R. Krausman, island fox on the Northern Channel editors. Ecology and management of Islands. Endangered Species Update large mammals in North America. 21:23-31. Prentice Hall, Upper Saddle River, NJ, SCHEMNITZ, S. 1994. Capturing and handling USA. wild animals. Pages 106-124 in T. NAUGLE, R. 2002. Immunocontraception of Bookhout, editor. Research and white-tailed deer at the national institute management techniques for wildlife and of Standards and Technology, habitats. The Wildlife Society, Gaithersburg, Maryland. 2001. Bethesda, MD, USA. Progress Report. The Humane Society SCHUYLER, P., D. GARCELON, AND S. ESCOVER. of the United States. Gaithersburg, MD, 2002. Eradication of feral pigs on Santa USA. Catalina Island, California, USA. Pages PARKES, J., R. HENZELL, AND G. PICKLES. 1996. 274-286 in C. Veitch and M. Clout, Managing vertebrate pests: Feral goats. editors. Turning the tide: The Australian Goverment Publishing eradication of invasive species. Service, Canberra, Australia. Invasive Species Specialist Group, PARKES, J., AND E. MURPHY. 2003. International Union for the Conservation Management of introduced mammals in of Nature, Gland, Switzerland. New Zealand. New Zealand Journal of SEWARD, N.W., K.C. VERCAUTEREN, G.W. Zoology 30:335-359. WITMER, AND R.M. ENGEMAN. 2004. PECH, R. 2000. Biological control of vertebrate Feral swine impacts on agriculture and pests. Proceedings of the Vertebrate the environment. Sheep and Goat Pest Conference 19:206-211. Research Journal 19:34-40. PEINE, J.D., AND J.A. FARMER. 1990. Wild hog SEIGMOND, O.H. 1973. The Merck veterinary management program at Great Smoky manual. Fourth Edition. Merck and Co., Mountains National Park. Proceedings Inc., Rahway, NJ, USA. of the Vertebrate Pest Conference SHWIFF, S. 2004. Economics in wildlife damage 14:221-227. management studies: Common problems PIMENTEL, D., L. LACH, R. ZUNIGA, AND D. and some solutions. Proceedings of the MORRISON. 2002. Environmental and Vertebrate Pest Conference 21:346-349. economic costs associated with non- SLADE, L.M., AND E.B. GODFREY. 1982. Wild indigenous species in the United States. horses. Pages 1089-1098 in J.A. Pages 285-303 in D. Pimentel, editor. Chapman and G.A. Feldhamer, editors. Biological invasions: Economic and Wild mammals of North America. The environmental costs of alien plant, John Hopkins University Press, animal, and microbe species. CRC Baltimore, MD, USA. Press, Boca Raton, FL, USA. STEGEMAN, L.C. 1938. The European RICHARDSON, C.D., P.S. GIPSON, D.P. JONES, in the Cherokee National Forest, AND J.C. LUCHSINGER. 1997. Tennessee. Journal of Mammalogy Extirpation of a recently established 19:279-290. feral pig population in Kansas. STINGER, F.J., W.T. SWANK, AND E.E.C. Proceedings of the Eastern Wildlife CLEBSCH. 1982. Some ecosystem Damage Conference 7:100-103. responses to European wild boar rooting ROCA, E., AND G. SEDAGHATKISH. 1998. Rapid in a deciduous forest. Research/ ecological assessment. U. S. Naval Resource Management Report No. 54. Station Guantanamo Bay, Cuba. The USDI National Park Service, SERO, Nature Conservancy, Bethesda, MD, Atlanta, GA, USA. USA. SWEITZER, R.A., I.A. GARDNER, B.J. ROEMER, G., AND C. DONLAN. 2004. Biology, GONZALES, D. VAN VUREN, AND W.M. policy and law in endangered species BOYCE. 1996. Population densities and

79 disease surveys of wild pigs in the coast deer-damage management: A review of ranges of central and northern designs and efficacy. Wildlife Society California. Proceedings of the Bulletin: In Press Vertebrate Pest Conference 17:75-82. _____, AND S.E. HYGNSTROM. 2000. Deer TAYLOR, D., AND L. KATAHIRA. 1988. Radio population management through hunting telemetry as an aid in eradicating in a suburban nature area in eastern remnant feral goats. Wildlife Society Nebraska. Proceedings of the Bulletin. 16:297-299. Vertebrate Pest Conference 19:101-106. TEER, J.G. 2003. Non-native large mammals in VITOUSEK, P. 1988. Diversity and biological North America. Pages 1180-1187 in G. invasions of oceanic islands. Pages 181- Feldhamer, B. Thompson, and J. 189 in E. Wilson, editor. Biodiversity. Chapman, editors. Wild mammals of National Academy Press, Washington, North America. The John Hopkins D.C., USA University Press, Baltimore, MD, USA. WAITHMAN, J.D., R.A. SWEITZER, D. VAN TURNER, J.W., JR., AND KIRKPATRICK, J.F. VUREN, J.D. DREW, A.J. BRINKHAUS, 1991. New developments in feral horse I.A. GARDNER, AND W.M. BOYCE. contraception and their potential 1999. Range expansion, population application to wildlife. Wildlife Society sizes, and management of wild pigs in Bulletin 19:350-359. California. Journal of Wildlife TURNER, M.G. 1986. Effects of feral horse Management 63:298-308. grazing, clipping, trampling and a late WARREN, R.J., R.A. FAYRER-HOSKEN, L.I. winter burn on a salt marsh, Cumberland MULLER, L.P. WILLIS, AND R.B. Island National Seashore, Georgia. GOODLOE. 1997. Research and field CPSU Technical Report 23. University applications of contraceptives in white- of Georgia, Athens, GA, USA. tailed deer, feral horses, and mountain UNITED STATES NAVY. 1979. Environmental goats. Pages 133-145 in Contraception impact assessment for the San Clemente in wildlife management. Technical Island feral animal and exotic plant Bulletin 1853. T. Kreeger, Technical removal programs. Wildlife and Natural Coordinator USDA, APHIS, WS, Resource Office, Staff Civil Eng., Naval National Wildlife Research Center, Fort Air Station, , CA, USA. Collins, CO, USA. _____. 1981. Final environmental statement WILLIAMS, E.S., AND I.K. BARKER. 2001. feral animal removal program San Infectious diseases of wild mammals. Clemente Island. Natural Resource Iowa State University. Press, Ames, IA, Office, San Diego, CA, USA. USA. VAN VUREN, D. 1992. Eradication of feral goats WITMER, G.W., T. DELIBERTO, K. and sheep from island ecosystems. VERCAUTEREN, AND P. BUTCHKO. Proceedings of the Vertebrate Pest 2003a. Mycobacterial diseases in Conference 15:377-381 wildlife. Proceedings of the Wildlife _____, AND B.E. COBLENTZ. 1987. Some Damage Management Conference ecological effects of feral sheep on 10:310-315. Santa Cruz Island, California. _____, R.B. SANDERS, AND A.C. TAFT. 2003b. Biological Conservation 41:253-268. Feral swine – are they a disease threat to VELTMAN, C., AND J. PARKES. 2002. The livestock in the United States? potential of poisoned foliage as bait for Proceedings of the Wildlife Damage controlling feral goats. Science for Management Conference 10:316-325. Conservation Report 204. New Zealand _____, H. MARTINS, AND L. FLOR. 2004. Department of Conservation, Lincoln, Leptospriosis in the Azores: The rodent New Zealand. connection. Proceedings of the VERCAUTEREN, K., M. LAVELLE, AND S. Vertebrate Pest Conference 21:217-220. HYGNSTROM. 2006 Fences used in

80 WOOD, G.W., AND R.H. BARRETT. 1979. Status of wild pigs in the United States. Wildlife Society Bulletin 7:237-246.

81