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Case Study: Predator control

Principles derived from studies of the role of learning in behavioral development have contributed to another applied management issue: non-lethal predator control. In 1974, Gustavson et al. first demonstrated the use of conditioned taste aversions to teach coyotes (Canis latrans) to avoid lambs. One to three exposures to lithium chloride treated lamb meat (to induce nausea and vomiting) were sufficient to prevent captive coyotes' pursuit of live lambs introduced to their pens. Although a single exposure did not suppress lamb attacks for some of the coyotes, it did reduce or eliminate their feeding on their kills, raising questions about the differential extinction of predatory action patterns.

Subsequent studies (e.g., Gustavson et al. 1982a) on rangelands in the western U.S. and Canada demonstrated the techniques' efficacy in reducing sheep depredation by coyotes. The success of lithium chloride baits has reduced the use of traps and poisons (which kill other harmless, and more endangered, species like black-footed ferrets and California condors) and shooting (which does not distinguish 'innocent' from 'guilty' coyotes), and preserves the coyote's role in the ecosystem. Conditioned taste aversions have also been used to reduce raccoon depredation on chickens (Nicolaus et al.1982), livestock depredation by other canids (Gustavson et al. 1983), and to protect sunflower crops from blackbirds (Gustavson et al. 1982b). Nicolaus et al. (1983) also paired the lithium chloride treatment with the painting of eggs in a study on crows to elucidate the role of conditioned taste aversions in the evolution of Batesian mimicry.

Conditioning has also been used with success to reduce human mortality from tigers (Panthera tigris) in India. Sanyal (1987 ) reported on the successful use of electrified manaquins dressed as fishermen, honey-collectors, and other likely victims on a tiger reserve. Only man-eaters were shocked and human casualties were reduced by half (from 45 to 22 per year) during the first three years of use. An understanding of how predators learn about acceptable and unacceptable prey can help wildlife managers reduce conflicts between humans and animals.

Gustavson, C. R., Garcia, J., Hankins, W. G. and Rusiniak, K. W. 1974. Coyote predation control by aversive conditioning. Science 184: 581-583.

Gustavson, C. R., Holzer, G. A., Gustavson, J. C. and Vakoch, D. L. 1982b. An evaluation of phenol methylcarbamates as taste aversion producing agents in caged blackbirds. Appl. Anim. Ethol. 8: 551-559.

Gustavson, C. R., Jowsey, J. R. and Milligan, D.N. 1982a. A 3-year evaluation of taste aversion coyote control in Saskatchewan. J. Range Manage. 35: 57-59.

Gustavson, C. R., Gustavson, J. C. and Holzer, G. A 1983. Thiabendazole-based taste aversions in dingoes (Canis familiaris dingo) and New Guinea wild dogs (Canis familiaris hallstromi). Appl. Anim. Ethol. 10: 385-388.

Nicolaus, L. K., Cassel, J. F., Carlson, R. B. and Gustavson,C. R. 1983. Taste-aversion conditioning of crows to control predation of eggs. Science 220: 212-214.

Nicolaus, L.K., Hoffman, T. E. and Gustavson, C. R. 1982. Taste aversion conditioning in free ranging raccoons (Procyon lotor). Northwest. Sci. 56: 165-169.

Sanyal, P. 1987. Managing the man-eaters in the Sundarbans Tiger Reserve of India - a case study. In: Tilson, R. L. and Seal, U. S. (eds.) Tigers of the world: the biology, bioploitics, management and conservation of an endangered species. Noyes Publications, Park Ridge, New Jersey. pp427-434.

Zahorik, D. M. and Houpt, K. A. 1981. Species differences in feeding strategies, food hazards, and the ability to learn taste aversions. In: Kamil, A. C., and Sargent, T. D. (eds.). Foraging behavior: Ecological , ethological and psychological approaches. Garland Press, New York. pp. 289-310.

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