Proceedings of the Ninth Mountain Lion Workshop - Carnivore ...

Wolf and Bear Detection of Cougar-Killed Ungulates on the Northern
Range of Yellowstone National Park
Polly C. Buotte, Wildlife Conservation Society, 2023 Stadium Drive, Suite 1A,
Bozeman, MT 59715, USA polly@3rivers.net
Toni K. Ruth, Wildlife Conservation Society, 2023 Stadium Drive, Suite 1A, Bozeman,
MT 59715, USA truth@centurytel.net
Howard B. Quigley, Craighead Beringia South, 3610 W. Broadwater Suite #111,
Bozeman, MT 59715, USA beringiasouth@beringiasouth.org
Maurice G. Hornocker, Wildlife Conservation Society, 2023 Stadium Drive, Suite 1A,
Bozeman, MT 59715, USA.
ABSTRACT The use of common habitat and prey resources can lead to both
exploitative and interference competition between cougars and other large carnivores.
Cougars generally require extended periods, typically 3 to 6 days, to consume a kill.
Although caching and concealing the kill in thick cover minimizes detection, other
carnivores do detect and encounter cougars at cougar-killed prey. If other carnivores
displace cougars, loss of biomass may potentially affect cougar predation rates, survival,
and success of rearing offspring. Alternatively, detection of kills potentially benefits
other carnivore species. But what factors influence detection of cougar kills by wolves
and bears, the cougar’s main competitors in northern latitudes?
As part of an 8-year study of cougar-wolf interactions on the Northern Range of
Yellowstone National Park, we examined factors that may influence whether wolves and
bears detected a cougar kill. Between 1998 and 2005 we cataloged 427 positive or
probable cougar-killed ungulates. Wolves visited 87 (20%) of these kills and displaced
the cougar from 27 (6%). We limited bear detection data to 234 kills made during
spring/summer and fall when bears were active. Bears visited 110 (47%) of these kills
and displaced the cougar from 43 (18%) of them. Because there were instances when we
could not determine whether visitation was simply scavenging or if displacement
occurred, we collapsed visitation and displacements into detections and analyzed wolf
detections separate from bear detections We used logistic regression and multi-model
inference to assess a number of models including explanatory covariates of habitat, prey
type and size, topography, and season. The odds of wolf detection clearly increased with
increasing wolf use and decreasing slope. We suspect slope had a modifying effect on
the wolf use variable, which was created from a 95% utilization distribution of wolf
locations and therefore does not account for terrain differences. Elevation, topographic
roughness, season, prey size, and distance to roads all had 95% confidence intervals
around beta estimates that bounded zero. Therefore given the variation in this dataset we
cannot be sure of these parameters’ true influence. The odds of bear detection were
higher for large prey than small prey and in the spring than in the fall, and decreased
sharply with the availability of more winter-kill carcasses. Slope, cover type at kill site,
and distance to roads all had 95% confidence intervals around beta estimates that
bounded zero. An index of bear use was not available for this analysis. Even in high
carnivore use areas, terrain features may hinder wolf or bear access and allow cougar
kills to remain undetected. These analyses illuminate factors that influence detection of
cougar kills, which may indirectly influence cougar survival through loss of prey
Proceedings of the Ninth Mountain Lion Workshop
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