Preference of Pygmy Rabbits (Brachylagus idahoensis) for Various Populations of Big Sagebrush (Artemisia tridentata)

Abstract

Pygmy rabbits were used in feeding trials to rate preference of 15 populations of 2 subspecies of big sagebrush (A rtemisia tridentata ssp. vaseyana, A rtemisia tridentata ssp. tridentata). Monoterpenoid content of sagebrush was determined for each population in the feeding trials and related to food preference. The rabbits showed no significant preference for one A rtemisia subspecies over the other; instead, selection was made at the population level. There was no significant correlation between monoterpenoid content and dietary preference of pygmy rabbits. It has been reported by a number of researchers that wintering mule deer prefer some populations and subspecies of big sagebrush (Artemisia tridentata) over others (Plummer et al. 1968, Hanks et al. 1971, Scholl et al. 1977, McArthur et al. 1979, Welch and McArthur 1979, Welch et al. 198 1). Hanks et al. (1971) and Sheehy (1975) reported that wintering sheep expressed similar differential preferences for populations and subspecies of big sagebrush. Determining wintering mule deer or sheep preferences for populations or subspecies of big sagebrush is an arduous and timeconsuming process. Paper chromatographic and ultraviolet light tests lack the sensitivity to differentiate preference among populations in a given subspecies (Hanks et al. 1971, and Stevens and McArthur 1974). Pygmy rabbits (Brachylagus idahoensis), described by Green and Flinders (1980) as having an obligatelike relationship with big sagebrush, may be useful as a laboratory test animal in evaluating the preferences of wintering sheep and mule deer for certain sagebrush populations. Even though big sagebrush comprises 97 to 99% of the winter diet of pygmy rabbits, nothing is known about the preference of these animals for certain populations or subspecies of big sagebrush (Wilde 1978, Green and Flinders 1980, White et al. 1982). This study is the first part of a two-part project aimed at determining the usefulness of pygmy rabbits in evaluating animal preference for certain big sagebrush populations. The purpose of this study was to determine if pygmy rabbits prefer some populations of big sagebrush over others. A secondary purpose was to relate the monoterpenoid content of big sagebrush populations to possible preference differences (Barbar et al. 1969, Sheehy 1975, Scholl et al. 1977, Nagy and Regelin 1977). Methods and Materials A laboratory colony of 15 pygmy rabbits was established at Brigham Young University for use in this study. Rabbits were trapped at the U.S. Sheep Experiment Station near Dubois, Idaho. Upon arrival at the laboratory, rabbits were dusted for fleas and placed in individual pens. Every other day, rabbits received fresh sagebrush (Artemisia tridentata ssp. vaseyana and ssp. tridentata) from various locations around Provo, Utah. Guinea pig food pellets containing 17.0% crude protein, 4.0% crude fat, 12.0% crude fiber, and mineral supplement were continuously available Authors are graduate research assistant, Range Science Department, Brigham Young University, Provo, Utah 84602; chairman, Botany and Range Science Department, Brigham Young University, Provo, Utah; research plant physiologist, USDA Forest Service, Intermountain Forest and Range Experiment Station, Shrub Sciences Laboratory, Provo, Utah 84601. Manuscript received September 25, 1980. to the rabbits. Ten rabbits were selected to determine preference for various subspecies and populations of big sagebrush. Fifteen populations of big sagebrush, which included eight populations of A.t. ssp. tridentata and 7 populations of A.t. ssp. vaseyana, were selected to test for pygmy rabbit dietary preference. Subspecies were identified by morphological and chemical criteria (Stevens and McArthur 1974, McArthur et al. 1979). Selection of the populations was based on sagebrush location and on the travel time needed to collect 2 distinct populations of each of the 2