Academic journal article The American Midland Naturalist

Social Group Patterns and Associations of Nonmigratory Elk (Cervus Elaphus) in Michigan

Academic journal article The American Midland Naturalist

Social Group Patterns and Associations of Nonmigratory Elk (Cervus Elaphus) in Michigan

Article excerpt

ABSTRACT.-We investigated the annual pattern of elk (Cervus elaphus) social group sizes and associations in Michigan's nonmigratory herd. Group observations were used to determine social group sizes and patterns throughout the year. Social group associations of individual elk were determined from 31 cow and 20 bull elk equipped with radio-collars. Bull and cow elk differed in their probabilities of belonging to single sex or mixed groups in 6 of 7 biological periods. Bull-only groups were small (mean = 1.3-2.7) and constant in size annually, while cow-calf (mean = 1.6-9.6) and mixed (mean = 5.2-35.1) groups were larger and varied in size throughout the year. Annual grouping patterns in Michigan were similar to grouping patterns observed for western North American elk herds. In contrast to other sedentary herds in stabilized habitats, elk in Michigan showed little annual (mean coefficients of association = 0.16) or seasonal (mean coefficients of association = 0.07-0.32) cohesion in social group membership, likely a result of seasonal limitations on the availability of food resources and/or hunting harassment.

INTRODUCTION

Annual variation in elk (Cervus elaphus) social groups tends to be pronounced, particularly for herds that are migratory, heavily hunted, and/or subject to seasonal resource limitations (Knight, 1970; Shoesmith, 1979; Franklin and Lieb, 1979; Clutton-Brock et al., 1982; Houston, 1982; Geist, 1982). Conversely, herds which are sedentary, not hunted, or subject to little seasonal variation in resource availability may show constant social group associations and less variability in social group size (Lieb, 1973; Franklin et al., 1975; Franklin and Lieb, 1979; Jenkins, 1980).

Franklin and Lieb (1979) identified three key social behavior parameters which change in elk populations: group size, stability and migration. They hypothesized that sedentary elk populations in a stabilized environment would favor the development of long term associations and bonding between individuals, resulting in stabilized cow-calf groups. They observed this pattern in a coastal California Roosevelt elk (C. e. rooseveltz) population (Franklin and Lieb, 1979). Similar results were reported for a sedentary elk population in Olympic National Park, Washington (Jenkins and Starkey, 1982) and for red deer (C. elaphus, Clutton-Brock et al., 1982). Studies of other elk populations have found little cohesion between individuals. Elk in the Sun River, Idaho, herd (Knight, 1970), the Yellowstone Mirror Plateau herd (Shoesmith, 1979), the Northern Yellowstone herd (Houston 1982), the Madison River, Montana, herd (Craighead et al., 1973), and elk in managed forests of coastal Oregon (Witmer, 1981) all showed little cohesion in social group membership. All of these studies, however, dealt with either migratory elk populations and/or populations in highly seasonal (less stabilized; typically managed forests characterized by large variations in food resources within the average lifetime of an elk) habitat rather than the stabilized (old-growth, stabilized meadows) habitats of Franklin and Lieb (1979) and Jenkins and Starkey (1982).

Moran (1973) evaluated many social group characteristics of the Michigan elk herd, a nonmigratory herd of ~1200 elk occurring in the northern Lower Peninsula. Although primarily managed forest, the small size of management blocks, the small overall size of the elk range, and the close association of elk with stabilized habitat openings in Michigan (Moran, 1973; Franklin and Lieb, 1979; Beyer, 1987; Bender, 1992) make the overall habitat much more stable than managed forests in the Western states. Although few elk were individually marked, Moran (1973) believed that social group membership in the nonmigratory Michigan elk herd was highly dynamic. Franklin and Lieb (1979), noting the stabilized habitat in Michigan and similarity between other grouping traits described by Moran (1973) and their grouping model, speculated that the dynamic nature of group membership reported by Moran (1973) was a result of methodological bias, although others disagreed (based on other behavioral traits; Geist, 1982). …

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