Pellet-Group Counts for Deer Census and Range-Use Index

Abstract

Since the original study by Bennett, English, and McCain (1940), wildlife workers have displayed increasing interest in pelletgroup counts both as a census technique for deer and as an index of deer use of the range. The purpose of this study is to increase the reliability of pellet-group counts as an index to deer populations and to deer use of range, and to investigate the problems of sampling pellet groups. Effective translation of pellet-group counts into tangible information largely depends upon reliable knowledge of defecation rate for deer. Several reports indicate that the defecation rate may not be a constant. Eberhardt and Van Etten (1956) reported a statistically significant difference (at the I per cent level) in the winter defecation rate for white-tailed deer (Odocoileus virginianus) by age (fawns vs. older deer) and by diet. Dasmann and Taber (1955) concluded that the defecation rate for Columbian black-tailed deer (Odocoileus hemionus columbianus) on their study area in California must vary seasonally, the variation apparently being attributable to changes in the diet and character of the forage. Longhurst (1954) reported an increased defecation rate for domestic sheep when placed on green forage-from 13.3 to 15.5 groups per day. E. A. Hewitt of Iowa State College states (letter of November 18, 1955) that for livestock: There is a very definite correlation with a decrease or increase in the amount of forage consumed upon the defecation rate .... Cattle usually defecate 10 to 24 times daily-more frequently if the food contains more water as in the case of succulent pasture. In addition, Eberhardt (letter of January 8, 1957) reports differences in the defecation rate for individual deer apart from age and diet. In the western United States, pellet-group counts usually are made on winter ranges of migra ory deer. Deer occupy these ranges for variable periods, but in Colorado, Utah, N vada, and portions of neighboring states, the p riod of use commonly extends from December into April. Since no data about defec tion rate covering this DecemberApril period have been published, and since other factors mentioned above are also involved, additional study seemed desirable. Thus, when the Colorado Department of Game and Fish constructed some deer-tight pastures on winter deer range to study forage competition between deer and livestock, the authors availed themselves of the opportu ity to determine the defecation rate for Rocky Mountain mule deer (Odocoileus h. hemionus) as an average for the entire wintering period. This paper reports the co-operative study conducted in these pastures from 1951 to 1955.