Phase I: Cougar Predation and Reproduction from 1987 to 1996

In Phase I of this study, which looked at cougar predation and reproduction in northern Yellowstone National Park and vicinity, 88 cougars were captured and 80 were radio-collared. Elk (Cervus elaphus) and mule deer (Odocoileus hemionus) comprised 98% of prey biomass and 81% of 302 documented cougar kills. Elk calves were the most important prey, mule deer were intermediate, and adult elk were least important relative to availability. Predation rates averaged 9.4 days per ungulate kill. Cougars killed 2–3% of the elk and 3–5% of the mule deer in the study area each year.

Grizzlyor black bears visited 19 of the 58 cougar kills documented from 1990 to 1995. Cougar predation provided an average of 1.9 kg per day of biomass to bears, or up to 113% of a bear's daily energy needs, a quantity that could be nutritionally significant to bears. Cougars displaced from kills by bears lost an average of 0.64 kg per day of ungulate biomass, or 17 to 26% of their daily energy requirement.

The reproductive success of male and female cougars was estimated using field observations and a paternity exclusion analysis on alleles documented at microsatellite loci. The mating system was polygynous. Resident males, as opposed to roaming males, sired nearly all litters. Males mated exclusively with females within their territories; females showed strong fidelity to their previous mates. The number of litters a male sired each year was correlated with his age and the number of breeding-age females present within his territory, but not with the size of his territory.

Updated 8/18/10