Western U.S. & Canada: 1881-2005
INTRODUCTION
This is a sampling of some recorded North American wild sheep die-offs that had data available fitting the needs of a particular research study. Many of these die-offs occurred because of domestic sheep. As stated here, many bighorn die-offs are not well-documented or not documented at all.
Note: Upon casual examination, I discovered at least one significant data discrepancy in the table below. The 1980 entry for Lava Beds National Monument mentions “stress factors” as the origin of a pneumonia outbreak with 76% mortality. However, other literature describing that outbreak states that all bighorns died, and domestic sheep were believed to be the cause (USFS 2001; Wehausen, Kelley, and Ramey II 2011). I grew up in northern California and know bighorns are long gone from the region’s lava beds.
Click here to download an Excel file of the table below.
REFERENCES
Cassaigne G., Ivonne, Rodrigo A. Medellín, and José A. Guasco O. 2010. Mortality during epizootics in bighorn sheep: Effects of initial population size and cause. Journal of Wildlife Diseases 46, no. 3 (July): 763-771.
U.S. Forest Service (USFS). 2001. A Process for Finding Management Solutions to the Incompatibility Between Domestic and Bighorn Sheep, by Tim Schommer and Melanie Woolever. N.p. http://www.fs.fed.us/biology/resources/pubs/wildlife/bighorn_domestic_ sheep_final_0806 01.pdf (accessed January 5, 2012). [govt. doc.]
Wehausen, John D., Scott T. Kelley, and Rob R. Ramey II. 2011. Domestic sheep, bighorn sheep, and respiratory disease: A review of the experimental evidence. California Fish and Game 97, no. 1 (Winter): 7-24. http://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=4651 1(accessed May 23, 2012).
Note: To see individual listing references, view the original document (Cassaigne, Medellín, Guasco 2010) from which the table was derived.