Plant Characteristics Related to Feeding Preference by Black-Tailed Deer

Six plant species of known preference by black-tailed deer (Odocoileus hemionus columbianus) were used to evaluate several factors thought to influence preference. Factors studied included chemical composition, in vitro fermentation of dry matter and cellulose, and effects of essential oils and water and methanol extracts on rumen microbial activity in vitro. Chemical analyses revealed considerable differences among species in all constituents; but, with the exception of moisture which was generally higher in the more preferred species, tissue components did not show any consistent relationship to preference. Fermentations of cellulose but not of dry matter were more closely related to preference than chemical composition and provided a good general indication of species preference. Similarly, the overall effects of oils and extracts on rumen activity suggested different preference ratings for the species, but results of the water extracts most closely approximated the established preference order. J. WILDL. MANAGE. 38(1):32-41 Like other herbivores, black-tailed deer show definite selectivity in their feeding. Thus, the animals have often been observed to prefer different parts of plants (Brown 1961:68-69, Oh et al. 1970:24) and to discriminate among and within species (Cowan 1945:131-137, Brown 1961:63-76, Crouch 1966, Miller 1968:144-148, Oh et al. 1970: 24). In addition, preference has been shown to vary by location and even on the same area during different seasons (Miller 1968:144-148, Brown 1961:69, Crouch 1966: 472-474, Crouch 1968:548, Oh et al. 1970: 24). Studies designed to identify factors influencing relative preference of animals for plants can provide information for formulating better management programs for both animal and plant resources. Many workers, therefore, have attempted to identify such factors by studying chemical composition and digestibilities of deer foods (Hellmers 1940, Einarsen 1946, Gastler et al. 1951, Bissell et al. 1955, Bissell and Strong 1955, Taber and Dasmann 1958:84-107, Brown 1961:83-89, Dietz et al. 1962, Short et al. 1966). Other investigators have studied effects on deer microbial activity of essential oils and individual terpenes isolated from pla ts (Nagy et al. 1964, Oh et al. 1967). Most investigations, however, were primarily concerned with the nutritive value f deer foods and included only proximate analyses which did not allow for determination of many individual chemical compounds. Much detailed work, therefore, is still needed to better understand factors influencing forage preferences of deer. In the Pacific Northwest, Douglas fir (Pseudotsuga menziesii) is utilized by deer, and in many areas intensive browsing seriously retards reforestation. Efforts to control browsing require an understanding of the role of Douglas fir in deer diets and its relative preference among associated species. In this study, therefore, we evaluated several factors suspected to affect preference using Douglas fir and five associated species of known preference to black-tailed deer during the dormant season. We determined concentrations of nutritional and nonnutritional chemical compounds and studied fermentabilities of the tissues and effects of their essential oils and extracts on rumen microbial activity in vitro. We gratefully acknowledge the coopera32 J. Wildl. Manage. 38 (1):1974 This content downloaded from 157.55. 39.139 on Sat, 26 Nov 2016 04:17:01 UTC All use subject to http://about.jstor. org/terms PLANT CHARACTERISTICS AND DEER FEEDING PREFERENCE ? Radwan and Crouch 33 tion of personnel of the Oregon Game Commission, Corvallis, Oregon, for use of the Cedar Creek deer enclosure at the Tillamook Burn to obtain the necessary plant material and deer. MATERIALS AND METHODS Plants and deer were obtained during February 1969 in or near a 340-acre deer enclosure at the Tillamook Burn in northwest Oregon. The area has been previously described by Crouch (1968:543).