A Cougar's Diet

Compared to other carnivores, members of the feline family have less diverse diets, eating mostly mammals and very little vegetable matter or fish. Deer account for the majority of prey consumed by North American cougars, but depending on regional variability, diet may also include elk, moose, bighorn sheep, pronghorn, caribou, coyotes, black bear, porcupine, beaver and small rodents. In recent years, scientists have found differences in both prey selection and predation rates based on age, sex and reproductive classes of cougars. For example, in Wyoming, Charles R. Anderson and Frederick G. Lindzey found female cougars prefer deer, whereas males preferred elk. Furthermore, solitary females have a higher predation rate, taking prey more often at every 7.3 to 7 days, compared to the males at 9.5 to 7.8 days per kill.

While capable of preying on almost anything -- even an animal five times its size -- some cougars develop a preference for one species, with that animal becoming the primary component of their diet. These "individual specialist" cougars can have catastrophic impacts to small and isolated populations of prey. Over a few winter months in southwestern Alberta, a single female cougar was responsible for killing 9 percent of the total bighorn population, including 26 percent of the lambs. These population declines abruptly stopped with the death of the cougar. In the Great Basin Desert, cougars shifted away from their primary prey, mule deer, and concentrated on an unexpected secondary prey, porcupines. A near extinction of the region's small, but once robust population of porcupines resulted in less than three years. Bottom line, if a cougar's specialized tastes involve an endangered or economically valuable species, it often doesn't end well for the cougar.