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Using Genetic Analyses to Identify Predators

Coyote and dog depredation account for much of the economic losses to livestock in the United States (National Agricultural Statistical Service, 2000, 2001). However, depredation by other species (such as members of reintroduced wolf populations) can be more socially and politically contentious. Predators are often elusive and attacks on livestock are not often witnessed but the species of predator causing stock losses can sometimes be ascertained from evidence near the carcass (such as scat or hair), the attack pattern, or size and spacing of bite wounds. However, these species assignments can be subjective and may be influenced by the experience level of personnel, the condition of the carcass, and knowledge of previous predation history at the site. Variation among conspecific predators in attack pattern, and inter-specific overlap in those patterns, may be another complication to accurate predator species identifications. There are wide ranges in accuracy of identifying species based on scat morphology (Farrell et al., 2000). Variation in individual feeding preferences (Fedriani and Kohn, 2001) may also complicate accurate species identification from scat. Sociological considerations also may influence results. For example, local or regional compensation schemes may unintentionally result in biases in predator species identification (Cozza et al., 1996). Using common field methods, the accurate identification of the gender of a predator responsible for a specific predation event is unlikely. Likewise, although there may be assumptions about which specific individual was responsible for an attack on livestock, those assumptions may not be based on any concrete data. Clearly, an unambiguous method to determine the predator species would remove identification biases. A method to identify the specific individual responsible for kills would benefit our understanding of predation and would be useful in certain situations. Both methods, even if used strictly in research situations, might ultimately result in improved approaches to minimize livestock losses to predation.

Direct, Spillover, and Intangible Benefits of Predation Management

Predation management is a controversial and often misunderstood reality of livestock management. Few on either side of the argument would believe that some sort of management is not necessary to limit livestock losses. Opposition to the lethal removal of predators characterizes most debates. While most of the opposition reflects a moral opinion about the manner in which people relate to the natural world, opponents of lethal control often argue that control is not economically justified.

Simple economic justification would require that benefits of predation management outweigh the costs. If the only goal of predation management were to be economically efficient, minimization of costs would be one of the primary objectives; however, current predation management philosophies focus on minimum disruption to natural processes. These include focusing lethal management of offending individuals and populations, and using methods (such as aerial hunting) that are expensive but highly selective and humane. Boardman et al. (1996) discuss that the objective of minimizing costs is the same as maximizing net benefits. The costs of management, while important, play a minor role in the selection of management strategies.

Costs of management include direct expenditures by producers for management programs, governmental expenditures for management and compensation programs, producer and governmental costs associated with preventing predation, and societal values associated with the predators removed. Costs of predation management programs are usually easier to quantify, can have significant variance and typically are concentrated to a few individuals, while the benefits are dispersed among many. For this reason, the authors intend to focus on the benefits of predation management programs.

Coyote Predation Management: An Economic Analysis of Increased Antelope Recruitment and Cattle Production in South Central Wyoming

In 1999, a project was implemented for the protection of antelope fawns in two areas of Carbon County, Wyoming. The project was funded by the Wyoming Animal Damage Management Board (ADMB) for the benefit of two antelope areas that were having trouble rebounding to their normal population levels after the severe winters of 1991 and 1992. While the Wyoming ADMB project's main focus was on enhancing pronghorn antelope fawn recruitment, the benefits of coyote population management could have “spillover” benefits to cow/calf producers in the coyote removal areas.

With the decline of the value of coyote fur in the late 1980s, coyote populations have increased in many areas of Wyoming, including ADMB area 63 and ADMB area 55, the two geographic areas in the study (Merrell and Shwiff, in review). ADMB area 61, another geographic area, was the control site. At the ADMB two predator management sites, there are, on average, 4,095 cows giving birth every spring. Since the decline of the sheep industry in these areas in the mid-1970s, no significant coyote management had been conducted. A study on the relationship of coyotes to mule deer fawn recruitment, done on and around area 63 in 1976-79, estimated the area's coyote population at 1 coyote/ 20.6 square miles (Springer and Wenger, 1981). Population data from the ADMB project for pre-treatment coyote populations in 1999 were 1 coyote/ 2.2 square mile, a nine-fold increase (Merrell and Shwiff, in review).

Prior to 1972, coyote populations had been suppressed by the use of broadbased poisons such as 1080, thallium and strychnine. After the ban on poisons, coyote populations continued to be suppressed by people hunting and trapping for fur. Many cow/calf producers who historically had been operating in lowcoyote population densities, felt that coyote predation on calves was not at a level to cause concern. Our study suggests that these coyote populations should be a serious economic concern to both the producer and the consumer.

Non-lethal Alternatives for Predation Management

The ethical milieu in which wildlife biologists and livestock producers work continues to change as the concepts of environmentalism and animal rights and welfare have become introduced and normalized (Singer, 1975). The American public, including livestock producers, are mired within a typically human psychological quagmire of having a high demand for benefit, but a low tolerance for cost — that is, economic forces. Americans tend to demand a cheap, reliable food supply, while simultaneously demanding the existence of animals that, through predation activities, drive up production costs. Ironically, members of the urban public who may find fault with food and fiber production practices are also the customers on which livestock producers are dependent. In the United States, predation management has evolved from an attempt to eradicate or limit predator populations to the application of focused approaches for minimizing the damage done by predators. For coyotes, very large scale population suppression (using 1080), was restricted and sometimes apparently ineffective (Wagner, 1988). Other authors could find little correlation between the number of coyotes removed and the number of sheep kills at a California ranch (Conner et al., 1998). Further studies suggested that at least in some areas, dominant territorial coyotes are responsible for most sheep predation but typical lethal control methods tend to bias capture toward coyotes that are less likely to be livestock killers, thus, typical lethal methods such as trapping, snaring, and using M-44s are sometimes inefficient for solving depredation problems (Sacks et al. 1999, Blejwas et al. 2002). Lethal control methods are also often at odds with conservation needs (Shivik et al., 2003; Haber, 1996) and the general public favors the use of nonlethal methods of predation management in many situations (Reiter et al., 1999). Non-lethal methods provide a means of keeping predators established, while protecting livestock from predation and thus, a great amount of effort has been spent identifying and evaluating non-lethal predation-management options (Linnell et al., 1996). Effects of territoriality may improve efficiency of non-lethal methods relative to lethal control. Because predators, such as coyotes and wolves, are territorial and relatively long-lived, multi-year effects of management actions are possible, in contrast to lethal control which tends to be required annually (Bromely and Gese, 2001a,b). One goal of nonlethal methods with territorial species is to develop a bioexclusive effect such that resident predators do not kill livestock themselves, but further prevent losses by excluding other predators from the area. The field and body of knowledge on non-lethal techniques is growing, and a need exists to categorize and understand the plethora of methods that are being advertised by both scientists and charlatans. The objective of this paper is to provide a descriptive outline of nonlethal methods for predation management and to identify hindrances to their use and future development. I have performed a basic search of non-lethal methods that are available. These methods have been categorized and then discussed. Note that inclusion of a method in this paper is not an endorsement or guarantee of effectiveness of the technique; the effective application of any management method will depend upon the particulars of the management situation. Many methods that are applicable in small pasture situations, for instance, may have little or no applicability in large, open-range situations.

Predation and Livestock Production: Perspective and Overview

1. Predation is a more serious problem for the livestock industry than most people realize unless they are somehow involved. This problem is almost certain to increase due to the dispersal of feral or wild hogs throughout the country and the expanding range of the reintroduced grey wolf.

2. Because predator species do not respect property or political boundaries, it is important that control efforts be conducted on a national, state or regional basis. At present, these efforts are carried out by the USDA-APHIS Wildlife Service Programs in cooperation with state agencies and livestock producers. Possibly some type of zoning could permit adapting management methods to the unique area being served. An appropriate approach for free ranging (fenced pastures) in the Southwest may be quite different from herded flocks or for farm flocks dispersed throughout the country.

3. Research relating to predation management should be a continuing effort, but should be a multidisciplinary effort involving those knowledgeable and close to the industries being served. Further, more research is needed to make existing management methods more effective, efficient and economical.

4. There is a need for more effective predator management tools including the limited use of effective and environmentally safe toxicants (see Fagerstone et al., this issue).