Habitat patches and their selection by wapiti cervus elaphus nelsoni and black tailed deer odocoileus hemionus columbianus in a coastal montaine coniferous forest

Hanley, T.A.

Journal of Applied Ecology 21(2): 423-436


ISSN/ISBN: 0021-8901
Accession: 005545835

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Habitat selection by female Rocky Mountain wapiti (C. e. nelsoni) and Columbian black-tailed deeer (O. h. columbianus) was studied during May-Oct. in a partially logged Abies amabilis forest on the west slope of the Cascade Range in Washington, USA. The general hypothesis was that ungulates prefer habitats where their net rate of intake of energy and/or nutrients (i.e., foraging efficiency) is greatest. Foraging efficiency is dependent on forage availability, forage quality and physical characteristics of the herbivore, including body size, digestive system and mouth size. Specific hypotheses tested were the following: graminoids would constitute a greater proportion of wapiti diets than black-tailed deer diets, while browse would constitute a greater proportion of black-tailed deer diets than wapiti diets; wapiti would prefer habitat patches where graminoid and forb availability was greatest, while black-tailed deer would prefer habitat patches where browse and forb availability was greatest. Six major plant community types were identified on the basis of multivariate analyses of floristics data. Two major gradients were identified as the principal factors associated with vegetation: soil moisture and stand age. The structural composition of plant cells and concentration of nitrogen were determined seasonally to assess forage quality. Composition of ungulate diets was determined seasonally by microhistological fecal analysis. Results showed that diets of wapiti and black-tailed deer were consistent with hypothesis number, and seasonal differences corresponded with expectations based on changes in forage quality. Habitat selection by wapiti and black-tailed deer was studied along gradients of soil moisture and stand age. Both visual observations and radio telemetry data were used. Black-tailed deer demonstrated a highly significant (P < 0.01) preference for xeric (browse and forb dominated) habitat patches, while wapiti demonstrated a highly significant (P < 0.01) preference for mesic (graminoid and forb dominated) habitat patches. Habitat preferences of blak-tailed deer along the stand age gradient were significantly (P < 0.01) correlated with browse and forb availability. Habitat preferences of wapiti along the stand age gradient were not significantly (P > 0.50) correlated with graminoid and forb availability, but this was not entirely unexpected, because forage availability in mesic habitat patches was relatively independent of stand age. These results wre consistent with 2nd hypothesis.