BOZEMAN – A study by the U.S. Geological Survey says elk in the Greater Yellowstone Ecosystem appear to be carrying the disease brucellosis at increasing rates.
Researchers found that the prevalence of the disease in the ecosystem’s free-ranging elk was between 0 percent and 7 percent in 1991-1992. That had increased to between 8 percent and 20 percent in 2006-2007.
Paul Cross, a USGS disease ecologist and lead author of the study, said high elk densities are probably responsible for the increased rates of brucellosis, which can cause animals including cattle, elk and bison to abort their young.
Biologists have known that the disease in parts of the ecosystem was sustained by the high densities of elk that congregate at feeding grounds in Wyoming in the winter, and that bison maintain brucellosis regardless of population size. But the new research, which focused on six herds, “shows that brucellosis may also be increasing in some elk populations that are distant from supplemental feeding grounds and bison.”
The study also notes that some herds in Montana are between five to nine times larger than they were in the 1970s.