High Elk Mortality: Wolves, Disease
by Wyoming Game & Fish Department
April 23, 2014
With the supplemental winter feeding program now concluding on most Wyoming Game and Fish Department elk feedgrounds, managers are reporting higher than normal calf mortality at a few feedgrounds, most notably the Camp Creek feedground south of Jackson and the Soda Lake feedground north of Pinedale. Mortality factors include disease and wolf predation. At the Camp Creek feedground, a significant number of the elk investigated involved both disease issues and wolf predation.
Department personnel collected samples from dead elk as well as whole carcasses, which were transported to the Wildlife Disease Laboratory in Laramie earlier this month. Wildlife disease specialists recently confirmed the presence of Fusobacterium necrophorum from many of the samples, the bacterium responsible for foot rot and necrotic stomatitis in elk. Foot rot is a term used for infection of the bacteria when it enters via cuts or other openings around the hooves; necrotic stomatitis is the descriptive term for infection of the same bacteria in the mouth.
F. necrophorum, has been linked to elk mortality on the National Elk Refuge as early as the 1920s. The most recent outbreak of note occurred in 2006. Hoof rot and necrotic stomatitis are previously observed ailments of elk associated with feedgrounds and often occur at low rates in early spring, prior to the ending of supplemental feeding.
This past winter, conditions in western Wyoming likely led to the increased prevalence of the disease, as above average snowfall in February and March, combined with above average temperatures, created some unusually wet conditions. F. necrophorum is a naturally-occurring bacteria that thrives in wet, anaerobic environments.
Northwestern Wyoming elk were exposed to many freeze/thaw cycles this winter, which formed heavy crusting of snow and areas of sharp, jagged ice and mud. Such conditions can cause lesions to an animalís hoof, or tissues between the toes, allowing the bacteria to enter the animalís system. From there, the bacteria can spread to vital organs, often overwhelming the liver, resulting in death. Calves are typically more susceptible, likely because they have not had a chance to build up immunity to the bacteria like adults.
Of the 2,000 elk counted at the Camp Creek feedground this winter, approximately 80 elk mortalities have been documented, mostly calves. It was determined that wolves played a role in the deaths of many of the elk at Camp Creek and to a lesser degree at Soda Lake. The percentage of calves counted at Camp Creek this year was up from past years at 34 calves per 100 cows. Given this, and the fact that Game and Fish managers had already proposed to decrease the number antlerless elk licenses offered in this hunt area, managers are not proposing any further adjustments to the proposed hunting seasons.
A total of 1,500 elk were counted at the Soda Lake feedground this winter and approximately 80 elk mortalities have been documented, again comprised mostly of calves. Managers note that although this level of mortality is higher than that observed during most winters, no hunting season regulation changes are necessary.