Age- and Sex-Related Differences in Fecal Pellet Dimensions of Moose

Abstract

Pellet groups from known age and sex classes of moose (Alces alces) were measured and weighed. Based on pellet volume estimates, 91% of the pellet groups could be identified as orginating from adult males, adult females, or yearlings. Discriminant classification functions correctly identified 6 of 7 pellet groups from areas of overlap among the classes of moose examined. Our results are discussed in reference to improving pellet surveys for moose population estimates and use of the technique for moose and other cervids. J. WILDL. MANAGE. 51(2):360-364 Pellet group surveys are often used to estimate ungulate population densities and trends, distribution, and habitat use (Neff 1968, Collins and Urness 1981, Rowland et al. 1984). This technique has been used for moose throughout their range (LeResche and Davis 1973, Franzmann et al. 1976b). A key variable in the equation used to derive a population index from pellet surveys is daily defecation rate. An estimate of 13 defecations/day has been used for cervids (Julander et al. 1963, Neff 1968). However, daily defecation rates for moose vary from 13 to 21 defecations/day (Timmerman 1975, Jordan and Wolfe 1980). Franzmann et al. (1976a) reported significant differences in daily defecation rates between male and female moose in winter with males having higher rates. Miquelle (1983) reported significant differences in daily defecation rates between calf and yearling moose during summer. Because of observed differences in defecation rates among age classes and sexes of moose, it is desirable to classify pellet groups to a specific age-sex class when conducting pellet surveys. In addition, identification of the sex and age class of moose depositing pellet groups may be useful in food habits, nutritional, and physiological studies of free-ranging animals. Bubenik (1982) stated that the size of wapiti (Cervus elaphus) fecal pellets depended on the age of the animal and that pellet shape is sex specific. He further suggested that measurements of wapiti pellets could be used to differentiate pellet groups according to the age and sex of the animals that deposited them. The purpose of this study was to determine if winter pellet groups of moose could be accurately assigned to adult male, adult female, or yearling classes, based on pellet dimensions. We suspected that there would be some overlap in the distribution of pellet size among the age-sex classes. We sought to identify questionable pellet groups (those within the areas of overlap) using discriminant classification functions. We thank D. G. Miquelle, J. M. Peek, and K. L. Risenhoover for collecting pellet groups, and Natl. Park Serv. personnel for permitting research at Denali Natl. Park. J. L. Davis, D. G. Miquelle, and D. W. Uresk reviewed an early draft of this paper. STUDY AREA AND METHODS Moose fecal pellets were collected from Denali National Park in central Alaska during the winters of 1982-83, 1983-84, and 1984-85. Moose in the park are habituated to humans and allow observers to approach as closely as 20 m. Only pellet groups that could be assigned to a specific age-sex class of animal were used. Positive identification of pellet groups was based on observing moose defecating, or collecting pellet groups from trails in the snow and subsequently identifying the moose making the trail. During the 1st 2 winters, 36 pellet groups were collected from adult males, 34 from adult females, and 6 from yearling moose. During winter 1984-85, 12 pellet groups were collected from adult males and 14 from adult females. Due to high calf mortality (>85%) the previous year, no pellet groups were available from the yearling cohort. We sampled pellet groups from ' Present address: P.O. Box 2275, Fairbanks, AK 99707.