Seasonal Changes in Defecation Rates of Free-Ranging White-Tailed Deer

Abstract

Defecation rates of 7 free-ranging female white-tailed deer (Odocoileus virginianus) were studied in a coniferous-deciduous forest in northeastern Minnesota. Defecation rates averaged 22.3, 27.0, 34.4, and 51.9 pellet groups/day during January-April, May-June, July-August, and September-December, respectively. Average defecation rate between autumn leaf-fall (15 Oct) and spring snowmelt (30 Apr) was 34 pellet groups/day. The same deer, when penned, defecated from 11 to 14 times/day. There was an average of 68.7 pellets/group. J. WILDL. MANAGE. 51(2):330-333 Counts of fecal pellet groups are used to estimate deer numbers and habitat use (Bennett et al. 1940, Neff 1968, Ryel 1971). Pellet groups deposited by white-tailed deer since autumn leaf-fall are usually counted in spring (Ryel 1971). Counts may be used directly to estimate year-to-year population trends or may be divided by pellet groups/deer/day to estimate deer numbers or deer-days of habitat use (Neff 1968). Defecation rates applied to white-tailed deer are based on 2 winter studies of penned white-tailed deer fed selected browse species in Michigan (Eberhardt and Van Etten 1956, Van Etten 1959), a study of penned white-tailed deer fed a commercial ration in Texas (Rollins et al. 1984), and studies of confined mule deer (0. hemionus) in western habitats (Neff 1968). Additional defecation rate information is needed because defecation rates may change seasonally with diet and metabolism, defecation rates for penned deer on artificial diets may differ from those of wild deer, and defecation rates may differ between species or within a species in different habitats (Ryel 1971). Also, information is needed for late fall, which is commonly included in pellet group counts but for which little defecation rate data are available for any North American deer (Ryel 1971). Studies of tame free-ranging deer ingesting natural forage were conducted in the Superior National Forest in northeastern Minnesota (47048'N, 91045'W) from 1977 through 1980. My objective is to report seasonal changes in the number of pellet groups deposited/day, based on direct observation of the tame, freeranging deer. I thank S. J. Burch, A. R. Conover, J. A. Hanson, K. A. Hunt, J. Lapham, L. Mason, J. McCarthy, L. J. Medved, G. Rasch, C. A. Schmidt, and M. L. Shedd for field assistance. D. J. Neff, L. D. Mech, L. A. Ryel, J. M. Sweeney, and P. J. Van Soest are thanked for their helpful suggestions with the manuscript.