Whiskey Mountain Bighorn Sheep / Past and Present
CHEYENNE– In the day to day managing of Wyoming’s game animals, wildlife managers must take a number of factors into consideration when establishing hunting seasons, license quotas and looking after the well-being of the game herds.
Such things as hunter success, habitat condition, winter loss and more can all affect the numbers of animals in a given population. One such factor that comes into play in Wyoming from time to time is disease. One well known disease problem wildlife managers have dealt with recently is the pneumonia outbreak that hit the Whiskey Mountain bighorn sheep herd in the early 1990s. In the winter of 1990-91, Wyoming’s largest bighorn sheep herd suffered through a die off that is affecting the sheep population more than 15 years later.
At that time, approximately 50 percent of a herd numbering close to 1200 animals succumbed to disease. Bacterial pneumonia was diagnosed as the culprit. Pasteurella bacteria can kill cellular material in turn allowing excessive fluid build up in the lungs of the affected animal. In the ensuing years, the Whiskey Mountain herd, which encompasses bighorn sheep hunt areas 9 and 10, has been the subject of extensive research as biologists are examining various strategies to try to determine the best management and disease treatment techniques to help the sheep.
The Whiskey Mountain herd received much of its fame through being the seed area where hundreds of sheep over the years were trapped and then transplanted to historic ranges throughout Wyoming. In addition, the sheep from Whiskey Mountain have also been used to start or supplement herds in other states. The last transplant from the herd took place in 1995 when 43 sheep were trapped to augment an existing population on the neighboring Wind River Indian Reservation.
In the years since the disease, the bighorns have been beset by numerous problems resulting in low lamb survival. In the late 1990s and early 2000s it was thought that selenium deficiency might be causing muscular problems with sheep. Mineral blocks with selenium were placed on the range for a three year period. That study had little effect on lamb survival or other problems caused by the pasteurella virus.
Lander area wildlife biologist Greg Anderson who has been involved in a great deal of research with Whiskey Mountain sheep says research is ongoing in an effort to improve lamb survival.
“Right now our data indicates that around 90 percent of the ewes are getting pregnant. We don’t know how many lambs are actually born, but by mid summer we typically have 60-65 lambs per 100 ewes and by the time lambs are on the winter range, that number has dropped to 20 lambs to 100 ewes. The problem is likely caused by a combination of habitat quality, disease and other factors.”
Currently, the Whiskey Mountain herd is estimated at around 40 percent of its 1980s population. In that heyday period, up to 80 bighorn sheep licenses were issued between hunt areas 9 and 10. In 2007, 12 licenses were issued between the two hunt areas. Anderson said that even without the pneumonia outbreak, it is doubtful eighty licenses would still be issued, as hunter habits have changed to affect the quotas that would be issued in this day and age. But there would still be more than the relatively few licenses now put out in the drawing each year.
“It should be noted that even with the die off, there are still a lot of sheep on Whiskey Mountain,” Anderson said. “It is our hope that upcoming research will provide us the information we need to assure that the Whiskey Mountain sheep herd is viable for years to come.”