Die-Off Tables

Western U.S. & Canada: 1881-2005

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.

bighorn die-off table_1881-2005

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.