Differences Between Douglas-fir Genotypes in Relation to Browsing Preference by Black-tailed Deer

Abstract

Tissue digestibility, essential oils, and levels of several chemical constituents were compared in foliage of Douglas-fir. Genotypes with different susceptibilities to deer browsing were used, and foliage was collected during the dormant season. In general, clones resistant to deer browsing had lower dry-matter and cellulose digestibilities, essential oils with greater inhibitory action on rumen microbial activity, higher content of fats, total phenols, flavanols, and leucoanthocyanins, and lower levels of chlorogenic acid. Results suggest that these resistance characteristics, especially the chlorogenic acid content, might be used instead of conventional bioassays with captive deer, to screen Douglas-fir breeding stock for resistance to deer browsing.

Palatability of Douglasfir Foliage to Mule Deer in Relation to Chemical and Spatial Factors

“…This evidence is usually based on comparison between different forage species and cause is generally attributed to free water content affecting succulence. Radwan ( 1972)) though, found a negative relationship between moisture and palatability between samples of different genotypes of Douglasfir, which agrees with present results. It is possible that this relationship is due to variable quantities of essential oils (Bonner and Varner, 1965;von Rudloff, 197 1) that have been found to be negatively associated with palatability of Douglasfir to blacktailed deer (Odocoileus hemionus columbianus) (Radwan and Ellis, 1975;Radwan, 1972).…”

Food Plant Selection by a Generalist Herbivore: The Moose

“…Also, the average food plant quality (i.e., protein, sugars, etc.) selected by different herbivores has been shown to be greater than the average found in the environment (Swift 1948, Bissell et al 1955, Bissell and Weir 1957, Radwan and Campbell 1968, Radwan 1972, Radwan and Crouch 1974. The moose (Alces alces), a generalist herbivore, had preferences for different plant species (Belovsky and Jordan 1978) and selected its diet to maximize net energy intake (Belovsky 1978).…”

Relationships between Sitka black-tailed deer and their habitat.

“…The content of secondary compounds varies with species and among individuals within species, and deer may select among them accordingly (Dimock and others 1976, Radwan 1972, Radwan and Crouch 1974. When deer are selective for this or other reasons, the amount of forage available is less than the current annual growth of the plants.…”