BLM releases policy to prevent disease in bighorn sheep

Separation is the best management to conserve bighorn sheep in areas of domestic sheep grazing, according to a new interspecies management policy by the Bureau of Land Management.

The agency released the Management of Domestic Sheep and Goats to Sustain Wild Sheep policy in order to institute collaborative management actions between wildlife agencies and private livestock industries that reduce the transfer of pneumatic diseases from domestic sheep and goats to wild sheep.

Bighorn sheep (Ovis canadensis) were once one of the most abundant wild ungulates in the western United States, but habitat loss and fragmentation, historical unregulated hunting and the introduction of domestic sheep grazing has caused significant population declines over the past century.

Wild sheep are highly susceptible to respiratory diseases carried by domestic sheep and goats. Studies have shown that respiratory diseases have a 90 percent mortality rate in wild sheep within two months of exposure, with lasting impacts on population recruitment. In the past, mortality rates have been so high that states have suspended hunts where bighorn sheep populations are unstable.

The agency’s new policy states that physical separation through man-made and topographic barriers is currently the only effective way of reducing disease transfer, however overlapping ranges and straying sheep can make contact unavoidable.

As part of this new policy, the BLM will create land use plans to prescribe effective separation between grazing domestic sheep and wild sheep. If contact occurs, despite continued efforts to avoid it, the agency urges livestock owners to consider transferring sheep or goats to other land allotments where risk of contact is significantly lower.

If allotment transfer fails, conversion of livestock from domestic sheep to cattle is highly encouraged. The policy also encourages the creation of emergency response plans if direct contact occurs between domestic and wild sheep, including the immediate removal of a diseased sheep or goat from the range.

Ultimately, the policy identifies the need for early action and collaboration between agencies and private livestock owners in order to prevent interspecies contact and effectively balance the multiple uses of BLM lands.

The new policy highlights some of the factors outlined in the joint issue statement by The Wildlife Society and the American Association of Wildlife Veterinarians in 2015. For more information about disease transfer in Bighorn sheep, see TWS’ factsheet.