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Prey Composition

Preliminary results indicate that, deer were the most commonly preyed upon item (66% of kills) followed by elk (29%) and non-ungulate (i.e., coyotes, raccoons, etc...) prey (5% of kills).

However, there are differences between male and female cougars.  Male cougars tend to prey on elk more frequently than female cougars.
 
Female Cougars:
  • Elk make up 25% of kills
  • Deer make up 72% of kills
  • Non-ungulate prey make up 3% of kills
Male Cougars:
  • Elk make up 45% of kills
  • Deer make up 44% of kills
  • Non-ungulate prey make up 11% of kills
 
Deer Predation
Species Composition of Deer Kills
Based on preliminary data, mule deer were the most common deer species killed by cougars (61% of deer kills), followed by white-tailed deer (23% of deer kills) and unknown deer species (16% of deer kills).

Age Composition of Deer Kills
Using preliminary data for all deer that were killed by cougars, we were able to determine the age composition of deer that were killed by cougars.  Our preliminary findings are that:
  • 47% of the deer that were killed by cougars were fawns
  • 36% of the deer that were killed by cougars were adults
  • 11% of the deer that were killed by cougars were yearlings
  • 6% of the deer that were killed by cougars were of unknown age
Deer that were of unknown age were likely fawns (only hair was found at the predation site) or we were unable to locate a lower jaw to correctly assign the deer to an age class.
 
Male and female cougars prey upon deer in a similar manner.  Male cougars kill fawns more frequently (49% versus 47%) and adults less frequently (34% versus 37%) than female cougars.  However, these differences are likely not statistically significant and may change over time.
 
Sex Composition of Yearling and Adult Deer Kills
Using preliminary data from adult and yearling deer (all species combined) that we were able to correctly identify sex from remains, we observed that:
  • 40% of the kills were bucks
  • 60% of the kills were does
Buck deer are killed most frequently during between August and November.  This coincides with the time of year that they are least vigilant and likely the most susceptible to predation.  During August, bucks are rubbing the velvet off their antlers.  This activity is noisy and reduces the vigilance of the deer.  During November, males are actively engaged in the rut and likely have reduced vigilance.
 
Elk Predation
Age Composition of Elk Kills
Preliminary results indicate that the most commonly killed age class of elk is calves (77% of elk kills).  Adult elk (14% of kills) and yearling elk (9%) make up similar proportions of the total elk kill.
 
Female cougar predation on elk is heavily focused on elk calves.  86% of elk killed by female cougars are calves, followed by adult elk (8% of elk kills) and yearling elk (6% of elk kills).
 
In contrast, male cougars prey most frequently on calves (58% of elk kills) followed by adult elk (28% of elk kills) and yearling elk (14% of elk kills).  In general, male cougars kill larger elk.  This is likely related to the larger body size of male cougars (150 lbs versus 100 lbs) which allows them to more effectively handle large prey.
 
Sex Composition of Elk Kills
Using preliminary data from adult and yearling elk that we were able to correctly identify sex from remains, we observed that
  • 32% of kills were bulls
  • 68% of kills were cows
In general, male cougars were responsible for almost all of the adult male (i.e., branch bull) mortalities.  Female cougars have killed adult male elk, but both of these elk were young (less than 3 years old) and were killed at a time of year when the elk had no antlers, or had small developing antlers.  Predation on large bulls is a relatively rare occurrence. 
 
 
Non-Ungulate Prey
The remains of non-ungulate prey were present at 5% of cougar kill sites.  Non-ungulate prey items found at kill sites included; badger, beaver, black bear, raccoon, cougar, coyote, domestic sheep, opossum and wild turkey.
A mature mule deer buck that was killed by a cougar.  Most of the predation on male deer occurs during the late fall and early winter.  This coincides with the time of year that male deer are the least vigilant and most susceptible to predation.










Elk calves are frequently killed by cougars, particularly during the summer months immediately after the calves are born.