Sheep Producers Could Benefit from Latest Bighorn Research
CHASE ADAMS
Senior Policy & Information Director
There can be no doubt that for nearly 40 years, Western sheep producers have faced few challenges as onerous as those brought about by the ongoing pressure to close grazing allotments due to pathogen concerns between domestic and bighorn sheep.
Questions and issues concerning bighorn die-offs have gone back to the 1970s and 80s, with pen studies (forced confinement of both species together in the same enclosure) and dubious connections to pneumonia related bighorn sheep deaths in the wild. Through the years, wild sheep advocates have moved the ball on the pathogens identified with these events, and the battle of which pathogen to blame continues. Yet, their target remains the same – domestic sheep. Specifically, domestic sheep grazing on federal lands has been in the crosshairs for far too long, leading to the loss of thousands of animal unit months across the intermountain states. This has impacted grazing in other areas, as well.
These issues have been exacerbated by outcome-driven science, and politics aimed at removing multiple-use mandates from federal lands. Nearly half of the United States domestic sheep flock spends some time on federal lands, and some 23 percent of domestic sheep allotments overlap with active or potential wild sheep habitat. This has put a countless number of existing allotments under constant pressure to voluntarily vacate active sheep grazing. When that doesn’t happen, activists seek to achieve their goals through threats and litigation.
While this has presented challenges for numerous producers and the rural communities that depend on them, there is positive news for these growers. First, research coming out of the U.S. Department of Agriculture Animal Disease Research Unit in Pullman, Wash., in conjunction with the rangeland resources at the U.S. Sheep Experiment Station in Idaho has been invaluable. Through ADRU research, scientists are able to better understand pathogen transmission – in both directions – between domestic livestock and wildlife. Through sampling and testing of other wildlife species, recently ADRU confirmed the presence of Mycoplasma ovipneumoniae (M ovi) in several other wildlife species (whitetail deer, mule deer, and a bison). M ovi is the pathogen that is currently identified as a major contributor to pneumonia-associated die-offs in bighorn sheep.
Bighorn advocates have repeatedly stated that M ovi originates in domestic sheep and domestic goats and is not carried by other species (aside from musk oxen). ASI has always stated that if you only look for one thing, you only find one thing. It’s no surprise to the association, that recent laboratory testing of other species has revealed the presence of M ovi in other species. These newly identified host species are consistent with the following quote, taken from a textbook entitled Mycoplasmas: Molecular biology, Pathogenicity, and Strategies for Control, “assumptions about restricted host range of mycoplasmas, based on the host from which they were first or frequently isolated, are usually made in the context of nearly complete absence of representative sampling of the vast majority of potential hosts.” Also, worth referencing are other peer reviewed publications that have already described Mycoplasma ovipneumoniae carriage in two other non-Caprinae species, including domestic cattle in Colorado (Wolffe, et al., 2010) and antelope at a wildlife conservation park in Qatar during a pneumonia outbreak (Gull, et al., 2014).
That bears repeating, the pathogen that for a decade has been the basis of the separation mandates between domestic and bighorn sheep is not solely carried by domestic sheep. This fact alone calls into question current management practices by state wildlife agencies of lethally removing bighorn sheep that have been in proximity of domestic sheep, and closing sheep grazing allotments due to concerns of pathogen transmission. This peer-reviewed and emerging research clearly shows those pathogens are present in wildlife, and are spread far more diversely than domestic sheep of European or Old World origin.
Additionally, wildlife research is calling into question what actually causes pneumonia-related die-offs in bighorn sheep. A 2015 article – Modeling Risk of Pneumonia Epizootics in Bighorn Sheep published in the Journal of Wildlife Management, found that “[r]isk was not associated with number of federal sheep and goat allotments, proximity to nearest herds of bighorn sheep…” and that “…factors associated with risk of pneumonia epizootics are complex and may not always be from the most obvious sources.”
Add to that, research being conducted at Montana State University – part of which was presented at the ASI annual convention in San Antonio – showing that these pathogens are endemic in bighorn sheep herds across the Greater Yellowstone Area research project. Furthermore, the research is confirming that the prevalence of the pathogens is not predictive of bighorn herd health in terms of pneumonia outbreaks.
Hopefully this new data will help bring about a more accurate and comprehensive discussion on respiratory disease in bighorn sheep, and that not only bighorn sheep populations, but other wildlife species can serve as a reservoir for harmful pathogens.
This is an issue that ASI remains dedicated to through member dues and Guard Dog funds, to stop the loss of sheep ranches through government action and activist litigation. With a greater scientific understanding of this complex problem, ASI is able to better advocate on behalf of its members. The association has continued to press for appropriations language, mandating federal reliance on USDA/ARDU epidemiology research for management decisions regarding disease issues.
As a last resort, ASI also advocates for the provision of alternative federal grazing allotments. ASI has also remained engaged in litigation on behalf of its producer members, sustaining traditional grazing and the economic base of rural communities. ASI continues to remain engaged with the land management agencies, Congress and state affiliates on the front lines of these issues.
While there is still much to do to get this information where it needs to go, the tide of the last four decades is starting to turn. Continued perseverance is needed, but the research is bearing out what producers have always known, and that is that proper grazing supports healthy rangeland and wildlife populations.