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DIMENSIONS: ecosystem |
Allometry- Body size relationships of ungulate resource division: A review of how morphology shapes: 1) Ungulate species distribution limitations during winter months and 2) Food selection in the Yellowstone region. I. Limitations on ungulate species winter distributions: * Morphology constraint: Smaller stature animals are not able to deal with deep snow like larger stature animals can. Animal chest height and foot loads are measures that determine an animal's ability to cope with snow depth and density. Foot load is: live wt / area of all hooves to dewclaws. Increasing chest height and decreasing foot loading determine relative ability to withstand snow conditions.
II. Food Selection during winter months: *Metabolic needs: Smaller animals, such as pronghorn and deer, need higher quality forage per unit body weight, than larger grazers, such as elk and bison. Forage is considered to have higher quality if it is high in crude protein. Large grazers more efficiently utilize large quantities of low quality food (ruminant animals), such as found on winter range grasslands. The proportion of grass in winter diet declines with ungulate body size. This means, larger grazers (elk and bison) are unselective, eating relatively high proportions of grass, as opposed to small selective mixed feeders (pronghorn, bighorn sheep and mule deer), which consume a relatively low proportion of grass during winter. - Relative narrowing of the face in conjunction with body size, are two measures that determine forage selectivity in ungulate species.
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