Winter Food Habits, Range Use, and Home Range of Antelope in Montana

Abstract

A study of the food habits, range use, and home range of pronghorn antelope (Antilocapra americana) with emphasis on the winter period was conducted in 1966-67 in Montana. Quantitative measurements of canopies and densities of taxa were made in five of the eight vegetation types available to antelope. The sagebrush-grassland type received most of the use by antelope, both in summer and winter. Most winter observations were in vegetation types where sagebrush was common. The winter diet, determined by plant utilization, consisted of 93 percent shrubs, 6 percent forbs, and a minor amount of grass. The diet, determined by analysis of rumen contents, consisted of 78 percent shrubs, 19 percent forbs, and a small amount of grass. Big sagebrush (Artemisia tridentata) provided 45 percent of the antelope food in winter. Results of five summer aerial censuses showed 32 male antelope per 100 females and 74 fawns per 100 females. Poor body condition of antelope and some fawn mortality in winter was possibly related to quality of sagebrush in the diet. Winter home-range size was determined for each of 16 individually marked antelope, three using telemetry. Eight of the marked antelope shifted their home range at least once. A yearling female had a home-range size of 5,574 acres and a yearling male, 4,160 acres. Six adult females had an average home-range size of 2,841 acres; three fawn females, 2,417 acres; and five fawn males, 1,580 acres. Information on the winter food and rangeuse habits of pronghorn antelope in Montana is somewhat limited. Cole (1956) reported the results of a comprehensive study of food and range-use habits with special reference to alfalfa, but data for winter were less comprehensive than for other seasons. Cole and Wilkins (1958) studied food and range use in reference to the effects on production of winter wheat. Martinka (1967) reported on mortality and food habits during a severe winter. Prominent among reports for other states are those of Einarsen (1948) and Buechner (1950) who gave information for Oregon and Texas, respectively. The principal objectives of my study, conducted during the summer of 1966 and winter of 1966-67, were to obtain quantitative data on food habits, range use, and home range of pronghorns in winter to help 1 A joint contribution from Montana State University, Agricultural Experiment Station, Project No. 400, Paper No. 934 Journal Series and the Game Management Division, Project Nos. W-98-R6 and 7, Montana Fish and Game Department. 538 evaluate current management practices (Bayless 1967). An additional parameter of the investigation was concerned with the effects of sagebrush removal on wildlife. The summer period was largely devoted to studies of the vegetation. The use of telemetry in winter greatly aided the study of habitat relationships and behavior. To the following, I wish to extend appreciation for their contributions: D. C. Quimby, Montana State University, for technical supervision and guidance in preparation of the manuscript; R. J. Mackie, formerly with the Montana Department of Fish and Game, for initial project planning; W. E. Booth, Montana State University, for verification of my identification of plant specimens; N. S. Martin, D. Pyrah, T. W. Mussehl, R. R. Knight, and P. Schladweiler, Montana Department of Fish and Game, for assistance during various phases of the study; personnel of the Bureau of Land Management, Lewistown District Office, for their cooperation; and to my wife, Judy, for encouragement and assistance. This content downloaded from 157.55.39.123 on Mon, 18 Jul 2016 05:48:20 UTC All use subject to http://about.jstor.org/terms ANTELOPE WINTER FOOD, RANGE, AND HOME RANGE IN MONTANA * Bayless