Deer Preference for Juniper Forage and Volatile Oil Treated Foods

Abstract

Cafeteria feeding trials were used to determine preferences by mule deer (Odocoileus hemionus) among alligator juniper (Juniperus deppeana), Utah juniper (J. osteosperma), and Rocky Mountain juniper (U. scopulorum) foliage and for pelleted feeds treated with their volatile oils. Deer exhibited a preference (P < 0.05) for alligator juniper, but did not differentiate between Utah and Rocky Mountain junipers. Preferences were inversely related to concentrations of volatile oil content of junipers. Terpene fraction of volatile oils also was related to preference, and deer selected against forages with higher concentrations of oxygenated monoterpenes. The forage species most preferred (alligator juniper) had the lowest absolute concentration of oxygenated monoterpenes. J. WILDL. MANAGE. 44(1):114-120 According to Goatcher and Church (1970), the sense of taste in higher animals functions in several processes, among which are: control of ingestive behavior, onset of specific appetites, and reinforcement in learning situations. Taste is important in nutrition. Theories on control of dietary intake have emerged from studies on energizing properties of sensory cues on behavior. One unifying concept is that taste, acting as a sensory cue, is involved in regulation of intake by linking relief of nutritional stress to some identifying sensory characteristics of food available. It is thought that the linking role may be both innate (acting in short term control) and learned (influencing long term regulation). The sense of taste has been thoroughly investigated in the laboratory rat, but other species, particularly wild ruminants, have received little study. Most investigators consider juniper a low-palatability, emergency browse for deer (Hill 1946, Smith and Hubbard 1954, Julander 1962). Yet Hill and Harris (1943) in South Dakota, and Lovaas (1958) in Montana, found varying degrees of use of common juniper (J. communis) and creeping juniper (J. horizontalis) by white-tailed deer (0. virginianus) and mule deer, respectively. Likewise, Anderson et al. (1965) found one-seed juniper (J. monosperma) and alligator juniper to be important yearlong mule deer foods in southeastern New Mexico. Junipers contain volatile oils that are inhibitory to deer rumen microorganisms (Schwartz et al. 1980). Inhibitory properties of these oils are proportional to their concentration and related to their chemical structure. When oils are fractionated into major components (monoterpene hydrocarbons, oxygenated monoterpenes, and sesquiterpenes), the oxygenated monoterpenes are the most inhibitory fraction. The role of these inhibitory properties of juniper oil as they relate to deer preference and selectivity of juniper is not understood. 1Data presented were collected by 2 Graduate Research Assistants at Colorado State University, W. G. Jobman and P. Smith. Financial support was provided by the USDA Forest Service. We also thank J. A. Bailey for graduate student guidance. 2 Present address: Alaska Department of Fish and Game, Moose Research Center, P.O. Box 3150, Soldotna, AK 99669. 3 Present address: U.S. Fish and Wildlife Service, Denver Wildlife Research Center, P.O. Box 2800, Kenai, AK 99611. 114 J. Wildl. Manage. 44(1):1980 This content downloaded from 157.55.39.104 on Mon, 20 Jun 2016 05:57:15 UTC All use subject to http://about.jstor.org/terms DEER PREFERENCE FOR JUNIPER Schwartz et al. 115 This is the 3rd phase of an investigation of the roles of volatile oils of Rocky Mountain, Utah, and alligator junipers in mule deer nutrition. The first 2 phases evaluated volatile oil content and composition of the 3 juniper species, and the role of these volatile oils and fractions on rumen microbial function (Schwartz et al. 1980). In this phase, we determined relative acceptance of 3 species of juniper and their volatile oil components using cafeteria feeding trials with mule deer. The following items were tested: (1) if deer preferred 1 of 3 species of juniper when equally available as raw forage; (2) if deer showed a selective response to ground and pelleted foliage of the 3 species of juniper in which differences in physical form were eliminated; (3) if deer differentiated among various levels of volatile oils normally encountered in natural vegetation; (4) if deer differentiated or showed preference among pelleted feeds dosed with equal concentrations of volatile oils from the 3 juniper species; and (5) if deer differentiated among 3 groups of pelleted feed dosed with equal concentrations of monoterpene hydrocarbons, oxygenated monoterpenes, and sesquiterpenes. We thank D. S. deCalesta for manu-