Abstract:
The objectives of this study were to quantify and describe:
(1) the major plant communities and their distribution, (2) the
distribution and movement patterns of large herbivores relative to
water, topography, and plant communities, (3) the daily activity
patterns of each herbivore, and (4) the borne range size of wild
horse bands and studs on a 376 km² area in southeast Oregon.
Distribution of plant communities about the area was
indicative of a history of overgrazing and fire. Communities in
low ecologic condition were associated with relatively level terrain
and basin areas.
Wild horses and bighorn sheep were year-around study area residents.
Cattle occupancy was from April through October, and intensive
deer use occurred from October through April. Deer movement to
and from the area was correlated with, but probably not caused by
cattle activities. Deer, however, preferred cheatgrass communities
previously grazed by livestock.
Ellipse estimates of home ranges for bands and studs averaged
28.3 and 25.8 km², respectively. Polygon estates for band and
stud home ranges averaged 11.8 and 12.3 km², respectively. Home ranges of bands and studs overlapped substantially, and no territorial
behavior was observed. Home range size showed a significant,
but weak, negative correlation with water hole density.
With the exception of bighorn sheep, habitat use by large
herbivores was negatively correlated with increasing slope. Species
order for progressively greater use of slopes was cattle, horses,
deer, and bighorn sheep.
Of the 4 herbivores studied bighorn sheep were the most
restricted in distribution. Progressive rankings of greater spatial
distribution were: bighorn sheep, cattle, horses, and deer. Patterns
of resource use by large herbivores did not always conform to mathmatical expectations.
