| Priscilla K. Coe, Bruce K. Johnson, John W. Kern, Scott L. Findholt, John G. Kie, Michael J. Wisdom |
| Authors are wildlife biologist, Ore. Dep. of Fish and Wildl., 1401 Gekeler Lane, La Grande, Ore. 97850, USA; wildlife biologist, Ore. Dep. of Fish and Wildl., 1401 Gekeler Lane, La Grande, Ore. 97850, USA; statistician, Western Ecosystems Technologies, Inc., 2003 Capitol Way, Cheyenne, Wyo. 83001, USA; wildlife biologist, Ore. Dep. of Fish and Wildl., 1401 Gekeler Lane, La Grande, Ore. 97850, USA; wildlife biologist, USDA For. Serv., 1401 Gekeler Lane, La Grande, Ore. 97850, USA; wildlife biologist, USDA For. Serv., 1401 Gekeler Lane, La Grande, Ore. 97850, USA. |
| Full text Article |
Abstract |
| Cattle graze seasonally on national forests in the Western United States, and mule deer (Odocoileus hemionus) and/or elk (Cervus elaphus) are sympatric with cattle in most of these areas. But the effects of interspecific interactions in terms of both the resources selected and animal distributions across landscapes are poorly understood. At the USDA Forest Service Starkey Experimental Forest and Range (Starkey), located in northeast Oregon, USA, elk and mule deer were free ranging within a 78 km2 study area enclosed by a 2.4 m high fence while cattle were moved among pastures in summer on a deferred-rotation schedule. Elk, mule deer, and cattle were located with an automated telemetry system from 1993–1996 and locations linked to a geographic information system (GIS) of Starkey. Our objective was to examine responses of elk and mule deer to cattle at multiple spatial and temporal levels. We compared elk and mule deer distributions, use of plant communities, and resource selection functions in one cattle pasture (24 km2) during early summer (cattle present in odd-numbered years) and late summer (cattle present in even-numbered years). Elk and deer differed in their spatial and temporal responses to presence of cattle. When cattle were present, the proportion of elk locations within the pasture decreased and use of the ponderosa pine/Douglas fir (Pinus ponderosa/Pseudotsuga menziesii) plant community within the pasture decreased in early summer and increased in late summer. The cattle resource selection function variable for early summer was not a predictor of elk distributions when cattle were present, but it was a predictor on years when cattle were absent. In late summer, the cattle resource selection function variable was a predictor of elk distributions regardless of presence of cattle. For mule deer distributions the cattle resource selection function variable was not a significant predictor in early summer (cattle present or absent), or in late summer when cattle were present, but it was a negative predictor of mule deer distributions when cattle were absent in late summer. Mule deer use increased or decreased in opposite direction from elk use in 3 of 4 season/year combinations for both pasture and ponderosa pine/Douglas fir. Our results suggest that competition for forage could occur between elk and cattle in late summer and that species interactions may be stronger between elk and cattle than mule deer and cattle. We recommend that managers look closely at stocking levels in late summer because cattle and elk use some of the same resources during that period, and to pay particular attention to the ponderosa pine/Douglas fir plant community where we found significant interactions between cattle and elk. |
| Key Words: Cervus elaphus, competition, distribution, habitat selection, Odocoileus hemionus, resource selection |