Aerial Counting of Two Montana Elk Herds

Abstract

Repeated aerial counts of elk (Cervus canadensis) were made during three winters in the Gallatin elk range, a narrow mountain canyon, and during one winter in the Sun River elk range, which covers a broad mountain front. Wide discrepancies in the results, within and between years, influenced mainly by snow conditions, were encountered in both areas. It is believed not feasible to apply statistical methods or reliability standards to the count results, and they are considered useful chiefly for following population trends, if evaluated in the light of weather conditions. When sportsmen representatives were included with the counting crews they were made aware of the inherent unreliability of the technique, but the practice required supplementary counts and aircraft, greatly increasing costs. Aerial counting has been used in elk management in Montana for about 20 years although the accuracy of counts made in mountainous, timbered terrain was doubtful. Twelve aerial counts of the Gallatin elk herd and four aerial counts of the Sun River elk herd were made from December, 1962, through April, 1965, to help evaluate aerial counting under Montana conditions. Unreliability in aerial counting of elk has been described previously. Buechner et al. (1951:84) reported large discrepancies in the numbers of elk seen on repeated aerial counts made during one winter in the Blue Mountains of Washington, and they stated: Little confidence may be placed in a single aerial count when the population is unknown and no data exist to indicate the probable magnitude of error. Anderson (1958:35) felt that aerial counts in Jackson Hole, Wyoming, were of value only for following herd population trends, and that differences in counting techniques, weather, and elk distribution had to be thoroughly evaluated. Robel (1960:103) studied elk migration in the Selway district of Idaho by repeated aerial surveys; the number of animals he observed per flight varied greatly. The importance of a good snow cover for aerial counts of elk was discussed by these writers as well as by Riordan (1948:412), Murie (1951: 290-291), and others. The assistance of the pilots, observers, a d photographers who participated in our counts was gratefully appreciated as were the assistance and guidance of Montana Fish and Game Department District Supervisors Robert L. Eng and LeRoy J. Ellig. AERIAL COUNTS IN THE