Mountain lions, also known as Cougars are opportunistic carnivores. In Utah, the mule deer makes up over 80% of the mountain lions’ diet. Cougars primarily eat large vertebrate prey. such as elk, bighorn sheep (Ovis canadensis), moose (Alces alces) and pronghorn (Antilocapra americana) may also be eaten. Although cougars feed primarily on large ungulates, small mammals such as porcupines (Erethizon dorsatum), lagomorphs (hares and rabbits), ground squirrels (Spermophilus spp.), and beavers (Castor canadensis) may also supplement the diet of cougarsCougars also occasionally feed on livestock and pets. Sheep and goats are the livestock most commonly taken by lions, but they also kill cattle, horses, and domestic animals, including dogs and cats.
Cougars are attracted to the movement of prey and this could be why prey species tend to ‘freeze’ after spotting a predator. Mountain lions typically stalk and then stalk or attack their prey after a short chase that rarely ends more than 100 yards.
Because cougars also feed on porcupines, they often have spikes on their feet and faces. This occasionally results in some fatalities when the spikes prevent the lion from eating or drinking. Cougars generally bury prey carcasses such as moose or deer after each feeding. This prevents scavengers such as magpies, ravens, eagles, bears, and coyotes from feeding on the carrion. Lions will eat about 70% of a large carcass before killing again.
Cougars can affect the trajectory of some ungulate populations. Lions were a major source of predation for one population of bighorn sheep in Alberta and were implicated in the decline of another bighorn sheep population, which began to avoid high-value foraging areas where they faced predators.
Logan and Sweanor (2001) reported that for cougars predation was the most important, proximate factor limiting a New Mexico mule deer (O. hemionus) population. In this case, lion predation reduces the rate of growth during a period of population growth and accelerates decline when a drought affects forage availability and condition.
Mountain lions annually reduce an estimated 15-20% of a mule deer population on the Kaibab Plateau, Arizona, 8-12% of a mule deer population on the Uncompahgre Plateau, Colorado, and 2-3% of elk and 3-5% of mule deer in the northern Yellowstone Ecosystem. However, predation by mountain lions does not necessarily suppress or regulate a prey population. Suppression is more likely in systems with multiple preys and multiple predator species. In these situations, predators that would normally decrease as their prey becomes less abundant are supported by other, more numerous prey species.
The potential effect of lion predation depends largely on the condition of the prey and its habitat. In areas where the habitat is in good condition, most individuals in the prey population are likely to survive in the absence of predation. Where prey is in poor condition due to diminished forage quality, individuals are more likely to die regardless of predation. Mountain lion predation is more likely to be additive to other causes of mortality when ungulates are in good physical condition. Conversely, mountain lion predation is more likely to be compensatory when ungulates are in diminished physical condition. Healthy prey populations typically have higher reproductive rates and offset predatory regulation by producing more young than are consumed by predators.