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Altering Predator Behavior

Two broad behavioral modification approaches have been widely used (Bangs and Shivik 2001). Primary repellents use disruptive stimuli that affect predatory behaviors by frightening or startling an animal. The limitation of primary repellents is that predators will quickly learn to ignore them. Secondary repellents use aversive stimuli, which are paired with a behavior in order to condition a predator against the behavior. Achieving effective and specific conditioning against behaviors such as attacking cattle may be extremely difficult under natural conditions (Shivik et al. 2003). It is important to understand that putting flashing lights in a pasture will not aversively condition wolves to not enter the pasture; to the contrary, wolves will learn to ignore the stimulus. Similarly, shooting wolves with rubber bullets when they enter a pasture will not necessarily condition the wolves to generalize and avoid the area or to avoid killing calves; rather, they are more likely to learn to avoid the person shooting at them.

Primary Repellents: Disruptive Stimuli

Simple Visual Stimuli

One of the most ancient disruptive stimulus techniques is a scarecrow. The concept can be extended to almost anything out of the ordinary that is placed in an area to frighten predators. A light in a field or a vehicle or some other large object in a pasture may keep some predators from entering, at least for a short time. As with scarecrows, of course, animals quickly become accustomed and habituated to passive disruptive stimuli. Moving the object around intermittently and randomly may slow the habituation process (Shivik and Martin 2001).

Noise

As with visual disruptive stimuli, sounds can frighten or startle a predator and limit access to an area. Radios, ultrasonic devices, and other noise placed in a pasture or pen and played loudly during the night will likely frighten intruding predators for a limited time (Blackshaw et al. 1990, Bombford and O'Brien 1990, Koehler et al. 1990). Exploder cannons are propane-powered disruptive stimulus devices that intermittently fire, producing a loud boom that may deter coyote predation for about 31 days (Pfeifer and Goos 1982, Andelt 1996).

Flashing lights, electronic guards

Linhart et al. (1992), determined that electronic guards reduced sheep losses by 60%. Electronic guards are randomly activated light and siren disruptive stimulus devices. They appear to be beneficial in areas such as bed grounds and are small, portable and flexible for various-sized areas. Habituation by predators is likely at about 91 days for coyotes (Linhart et al. 1984). Other researchers have extended the electronic guard concept to radio-activated guards for wolves, which activate in response to the presence of a radio-collared animal and may delay habituation (Breck et al. 2003).

Fladry

An ancient Eastern European technique used to capture wolves is to drive them along a narrowing boundary constructed of flags hung beneath a rope. Wolves tend to not cross the human-constructed line and can be driven into a corral or net-trap. Some research indicates effectiveness of fladry with captive wolves, but reports of effectiveness under field situations with other predators have varied (Musiani and Visalberghi 2001, Shivik et al. 2003, Musiani et al. 2003).

Chemical repellents

There are no selective chemical repellents that affect only individual species (Lehner 1987). The sensory physiology of all mammals is similar, and thus a selective chemical repellent which will repel predators, but not affect livestock or humans has not been identified. However, some manufactures claim efficacy of their predator repellents. Renardine, for example, is bone tar oil that is claimed to be a repellent for coyotes. The product is used to coat fence-lines and posts. Like any novel stimulus, strange smells posted around a pasture may deter predators, but its effectiveness may be limited due to habituation.

Biological odor repellents

Predators such as wolves and coyotes use scent marking to delimit territories (Shivik et al. 1996) It may be possible to mimic territorial behaviors by surrounding pastures with artificial scent marks that could repel intrusions. This technique can be used on areas of various sizes, but it has not been thoroughly evaluated and its effectiveness is in question.

Disruptive harassment

In some situations, it may be possible to guard an area and then, if a predator enters a livestock area, use rubber bullets or other nonlethal projectiles to prevent predation. This technique may be beneficial because it is selective. Clarkson (1989) reviewed shotgun weapons and Hunt (1985) examined multiple methods for bears. A variety of weapons exist such as paint-ball type weapons filled with capsicum powder (the active ingredient in hot pepper), and low-power lasers developed for military and law-enforcement applications. Some tests indicate that lasers are effective for dispersing some birds, but may not be effective on many mammals.

Guarding animals

The use of guard dogs originated in Europe and Asia thousands of years ago, and Americans have been using guard dogs and other guard animals since the mid-1970s. Some studies have shown that producers that use dogs are pleased with their effectiveness, and that guard dogs are a cost-effective means of reducing predation for coyotes and other predators (Andelt 1992). The use of other guard animals has also been investigated (Meadows and Knowlton 2000).

Secondary Repellents: Aversive Stimuli

Conditioned Taste Aversion

Conditioned taste aversion (CTA) is a powerful training technique. CTA uses a less-than-lethal poison that is fed to a predator after it has consumed a type of food; the poison causes illness and the illness causes an intense aversion to the flavor of the food. However, due to a variety of logistical and biological constraints, the technique does not appear to be effective in field situations, and is thus not used widely (Dorrance and Roy 1978, Conover and Kessler 1994). CTA is excellent for deterring eating behaviors, but is not especially effective at modifying killing behaviors.

Diversionary feeding

It may be useful to increase game availability, or place carcasses or other alternative food supplies in areas near livestock and allow predators to consume these resources, so that livestock remain unmolested. Bear damage to trees was limited by alternate feeding (Ziegltrum 1990), but other authors suggested that alternative feeding may not be effective in the long-term (Boertje et al. 1992).

Reproductive inhibition

Reproductive inhibition may be a useful tool for minimizing predation by territorial predators. Earlier work indicated that coyotes without pups killed fewer sheep (Till and Knowlton 1983). However, appropriate chemical contraceptives and delivery systems have not yet been developed, so no inexpensive and practical methods for reproductive inhibition are currently available.

Translocation

If predators and livestock do not occupy the same place, they cannot interact, and thus translocation is sometimes advocated as a damage management strategy. Some studies reported a decline in killing after predators were removed (Armistad et al. 1994, Waite and Phillips 1994, Stander 1990). However, translocated predators will often attempt to return, cause similar or worse conflicts, or die (Linnell et al. 1996).

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