The last half-century has seen a dramatic recovery of the cougar (Puma concolor), once nearly extirpated as a result of aggressive predator-bounty programs that sought to eliminate these animals throughout most of the country. Cougars now occupy most western states and have started to reoccupy historic ranges east of the Rockies. Beyond cougars' intrinsic value, scientists have uncovered beneficial effects of such carnivores on ecosystem processes and prey populations. But in rare cases, diet choice can also have negative consequences.
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.
A Taste for Quills
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.
- Journal of Wildlife Management: Estimating Cougar Predation Rates from GPS Location Clusters
- Cougar: Ecology and Conservation; Maurice Hornocker, Sharon Negri
- Proceedings of the Royal Society of the Biological Sciences: Stochastic Predation Events and Population Persistence in Bighorn Sheep
- Conservation Biology: Near-Extinction of Porcupines by Mountain Lions and Consequences of Ecosystem Change in the Great Basin Desert
Barbara Cozzens has been writing for more than 20 years. Her work has appeared in publications of the Nature Conservancy, the World Bank Group, National Geographic Society, Duke University and others. Cozzens holds a Bachelor of Arts in biology from Colgate University and a Master of Environmental Management from Duke University's Nicholas School of the Environment.