Domestic Sheep Grazing

Considerable research over the past two decades has shown that healthy domestic sheep carry strains of respiratory tract bacteria that almost always cause fatal pneumonia in bighorn sheep if contact between the two occurs. Entire herds of bighorn have died out following contact with domestic sheep. These facts alone explain much of the historic decline of bighorn sheep in the west after domestic sheep grazing began in the mid 1800s.

Domestic sheep have not been permitted to graze within bighorn sheep habitat in the Sierra Nevada for decades. However, domestic sheep have continued to graze in close proximity to bighorn habitat along the base of the eastern Sierra during summer. Domestic sheep are known to stray from their flocks and can end up in bighorn sheep range. This has been documented on multiple occasions in the past few years. While no actual contacts between these stray domestics and their wild cousins have been known to occur in recent decades, there have been some very close calls.

When the question of endangered species status for Sierra bighorn was raised, it became apparent that it was only a matter of time until contact between bighorn and domestic sheep would occur, with disastrous consequences for the Sierra bighorn population. Because of the nature of the regulatory processes governing grazing on public lands, endangered species status was necessary in order for the U.S. Forest Service to close those grazing allotments that posed a threat.

Following the emergency listing of Sierra bighorn as an endangered species, the U.S. Fish and Wildlife Service began working with the Forest Service and other land management agencies to solve this problem. Foundation President John Wehausen participated in a working group which analyzed each allotment for specific risks and then recommended solutions that would mitigate those risks of domestic sheep meeting bighorn. Risks for two allotments could not be mitigated, and these allotments were closed by Inyo National Forest.

The Los Angeles Department of Water and Power also chose to close all allotments on their lands rather than try to mitigate threats. Most of those allotments were in the Mono Basin where the domestic sheep grazed largely on irrigated meadows during summer. By closing those allotments, LADWP freed up more water to help Mono Lake rise to its court-mandated level.

Due in large part to cooperation between these different agencies and stakeholders, threats to Sierra bighorn from domestic sheep grazing were eliminated within a year of emergency endangered species listing. Future reintroduction of bighorn to currently unoccupied herd units may require further analysis of nearby grazing allotments.