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NONLETHAL CONTROL OPTIONS FOR PREDATION
MANAGEMENT ON WILDLIFE
WILLIAM F. EDMISTON, D.V.M., Sheep and Goat Predator Management Board, P.O.
Box 3543, San Angelo, Texas 76902; e-mail edmiston@wcc.net
DALE ROLLINS, Department of Wildlife and Fisheries Sciences and Texas Agricultural
Extension Service, 7887 U.S. Highway 87 North, San Angelo, Texas 76901-9714; e-mail
d-rollins@tamu.edu
Abstract: Changing mores about predators and their management over the last thirty years
have prompted the need for nonlethal approaches to predator management. Considerable
effort since that time regarding cultural practices (e.g., shed-lambing), fencing, and guarding
animals have provided management alternatives for livestock producers who suffer losses
from predators. However these alternatives may not be applicable or effective when
attempting to minimize wildlife losses to predators. We discuss (a) current efforts on the use
of immunocontraceptives as a means of reducing coyote (Canis latrans) populations, and (b)
general guidelines for habitat management as a means of dissipating predator-induced
mortality on upland game birds and deer (Odocoileus spp.).
WHY LETHAL CONTROLS?
depredation by raccoons (Procyon lotor).
Further, tools like the Livestock Protection Collar offer control for the specific coyotes that are causing livestock damage, but such expanding human population, changing land remedy for excessive predation on big game environments, and changes in the sheep and goat industry in Texas have increased the approaches to predation management. Inthis paper we discuss some new and old IMMUNOCONTRACEPTION
approaches to reducing predation losses todeer (Odocoileus spp.) and quail (Colinus virginianus and Callipepla squamata). a series of approaches aimed at inducingcontraception or sterility in coyotes. The basic concept of immunocontraception is to control to protect wildlife has some inherent differences than that designed to protect process (DeLiberto et al. 1998). Research, funded in part by Sheep and Goat Predator affecting wildlife populations, e.g., nest National Wildlife Research Center Predator higher dose is effective, or if coyotes use a Millville, Utah and Utah State University different biological pathway not affected by since 1995 to test immunocontraceptives in coyotes. Lethal techniques to resolvelivestock-predator conflicts are becoming less acceptable to the public due to changing social values, and this research can assist in means for pregnancy termination in coyotes.
Bromcriptine, although structurally similar situation. This research was undertaken with to cabergoline, differs in its affinity for socially-acceptable and environmentally-safe alternative to lethal control techniques.
should be deliverable by an oral route, such as the method used for oral rabies bait drop, appear to have potential usefulness only on studies are undertaken based on the premise that provisioning of pups is a key factor in constraints of contraception based on time established territories (Bromley 2000). Thisbehavior often results in coyotes located on one ranch where they are acceptable to land adjacent properties, with resulting wildlife- luteinizing hormone (LH) and folliclestimulating hormone (FSH) producing cells of the anterior pituitary gland. Damage to identified to reduce fertility in coyotes. It is sterility of both sexes, perhaps permanently.
pregancy in dogs, and patent rights willsoon lapse on this drug. Research at NWRC the last two years was unable to document pregnancy. Recent work in Australia in red initiate development of an orally-deliverable currently underway to determine whether a studies are directed at the development of a safe, legal, and ethical population control raccoons. However, Ratnaswamy et al.
(1997) used the same estrogen compoundand failed to demonstrate a CTA of CONDITIONED TASTE AVERSION
raccoons for reducing depredation of eggsof sea turtles.
nest depredation may be conditioned taste effectiveness of lithium chloride-treated which animals associate the taste of a food consumption. The predators show that they were equivocal; one study site demonstrated have acquired this learning or, conditioning, a successful CTA and the other did not.
offending food wherever it is encountered refinements with dosage, and perhaps other long after they have fully recovered from chemicals, may have provided better results.
Also, the mesomammal community wascomplex at Hernandez’ study sites, and thus directed at providing a nonlethal means of (Gustavson et al. 1974, Ellins et al. 1977).
Results have been mixed (Burns 1980, Nicolaus (2000) provide a review of various CTA trials to reduce livestock predation and the biology of how CTAs are developed and implemented. Similarly, Conover (1989)and Nicolaus (1987) provide reviews of (a) predators need to be of relatively small using CTA for reducing egg depredation by (b) predators need to occupy small,overlapping home ranges; rather simple, i.e. low species diversity; (d) the are to be treated needs to be rather Nicolaus 1982, Conover 1989). Of theaversive chemicals tested, emetine hydrochloride appears to be one of the mostpromising, but emetine is hazardous to use and thus it’s potential for field applications is limited (Conover 1989, 1990). Semel and prickly pear, especially if conventional grass preferred and the bottom of the fence should microhabitats are limited (Slater et al.
Sometimes modifications to the fence, e.g.,a buried net-wire “apron”, or an offset electric tripwire (or 2) spaced about 6 inches outside the fence and about 10 inches high, suitable nesting clumps per acre. A suitable nest clump will be about the diameter of a effectiveness. Fences are not generally not basketball and at least 18 inches in height.
effective deterrents for foxes, bobcats, and raccoons because of their tendency to climb 13 feet. Slater et al. (2001) reinforced this threshold when they found that simulatednests placed in prickly pear had no higher HABITAT ENHANCEMENT
survival than grass nests at sites thatfeatured at least 300 grass clumps per acre.
minimizing predation management on one’s prickly pear survived higher than those in target species of wildlife is to tailor the nest sites. Slater et al.’s data suggest that habitat in such a way that it facilitates the the best offense against nest predators is a prey’s needs more than the predator’s. This maxim is easy to comprehend and visualize, opportunity to nest at a number of locations but more difficult to quantify. Generally predators’ ability to locate the nest. Anyone provide a greater quantity of suitable habitat who has ever played a “shell game” can relate to how such laws of chance operate.
The more “shells” the better the odds that the “dealer” (in this case the quail) will win.
predators’ search efficiency is diluted, and Conversely, as the number of grass clumps diminishes, it only enhances the predator’s odds of locating a nest. The latter situationis currently a topical problem in quail success is typically “low”, e.g., less than 30 2001b, this volume). Bobwhites tend to nest in past-year’s growth of a bunchgrass s u r r o u n d i n g s w e r e “ l a r g e l y like little bluestem (Schizachyrium indistinguishable”, but only 28% for nests scoparium; Guthery 1986, Lehmann 1984).
situated in clumps of grass conspicuously Scaled quail in Pecos County nested almost better than their immediate surroundings.
entirely in tobosa (Hilaria mutica; Buntyn et Buntyn et al. (2000) reported nest success al. 2000). Both species will also nest in 1999 nesting season. This high success rate exemplifies Lehmann’s observation about using a “softball model” for assessing recommended that suitable loafing coverts, e.g., lotebush (Ziziphus sp.), be spaced nomore than a softball-throw apart (ca. 150 feet). For proper nesting habitat, a softball on several fronts relative to ranching, we tossed pitching distance (46 feet) should not believe it does provide an important nesting be visible to the thrower. Such conditions substrate for quail, and especially in drought will be satisfied by bunchgrass densities of Plains is currently (i.e., nesting season of inches in height or in fairly dense tobosa microhabitat if not for prickly pear. Whilewe can offer no specific recommendations of prickly pear density for quail nesting, a“good” mix of prickly pear and perennial grasses seems to provide a quality nesting coyotes, especially until they are about eight weeks of age. Although coyote predationon fawns can be a management constraint in some areas of Texas, comparable thresholds rehabilitating nesting cover. Good grazing for delineating good fawning habitat are not management which may entail rest, reduced “some is good and more is better” (R.
rotational schemes should be incorporated to promote a higher range condition, i.e., Department, personal communication).
typically the taller-growing bunchgrasses Generally areas of taller grasses, e.g., higher range condition or ungrazed blocks ofConservation Reserve Program pastures, are need generic “escape cover” which includes herbaceous cover (i.e., grass), screeningcover (e.g., low brush and broomweed), and escape cover which may include some areas brush control. Rollins (1983) reported that Ashe juniper (Juniperus asheii). Such sites may be important until grass cover increases describe the “cone of vulnerability” of quail to suitable levels to provide protection for vulnerability” for threats from ground- individual trees into brush piles, and their subsequent burning, may be undesirable for parameters relate to brush and herbaceous LITERATURE CITED
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