Perceptions of Mountain Lions 129higher than that documented for other mountain lion populations under study. Even
before mountain lions were killing deer in the central Black Hills, DePerno et al. (2000)
estimated the annual survival of adult female white- tailed deer at about 57%. The har-
vest rate was estimated at 10%, which meant that 33% of adult females were dying
from other causes; in that study, those causes were coyote and domestic dog preda-
tion, malnutrition, sickness, and other unidentified agents of mortality. If there were
40,000 deer in the Black Hills, then about 13,000 deer would have been dying from
causes other than harvest before the time when lions became a dominant predator in
the region. As a result, the predatory impact of lions on prey in the Black Hills region
could be negligible, because other sources of mortality would be compensating for
predation.
The objective of one of our studies (Simpson 2015) was directly related to assess-
ing the effects of mountain lions on elk in the Black Hills. The individuals who testi-
fied that mountain lions were reducing game populations had used this big game
species as an example of the impact of lions. The elk population had been reduced in
the recent past by a high level of harvest because of complaints from landowners
who were experiencing damage (loss of crops, damage to fences) to their ranches. How-
ever, the reduced number of elk also was associated with lions, possibly because of a
decreased rate of growth, other wise known as a “predator trap” (e.g., Gasaway et al.
1992) perpetuated by a relatively high lion population. Some evidence in support of
this hypothesis had been collected by South Dakota Game, Fish and Parks biologists
who were conducting a study on elk in Custer State Park. Their initial findings indi-
cated low survival of elk calves owing to lion predation. We were funded to conduct a
companion proj ect on elk west of Jewel Cave National Monument and north of High-
way 16 to the Deerfield Lake Region of the Black Hills (Simpson 2015). The study area
represented over 30% of the Black Hills region in South Dakota, and surveys indicated
that there were as many as 1,000 elk occupying the area. We radio- collared 40 cow elk
per year for two years and subsequently collared close to 40 elk calves per year for the
study. Results of our study indicated that elk calf survival averaged 75% and was actually
higher than had been found in most elk populations in western states; it was equivalent
to what had been found for elk calf survival in eastern states ( table 8.11). Furthermore,
the average weight of cow elk in this region of the Black Hills was high, another indica-
tion that this population was doing well. Thus, the conclusion from the study was that
elk were not being affected to a significant degree by mountain lions. Nevertheless, of
the mortality that was documented on these calves, at least 75% was from predation;
thus, lions were killing some of the calves. It should be noted that the lion population
was in the pro cess of being reduced while we were conducting our study, and thus,
any reduction in the lion population could have resulted in fewer elk calves killed by
lions. Furthermore, in contrast to what had been presented at the Game and Fish Com-
mission meeting, there was some published information that indicated that reducing