Here are relevant excerpts from the US Fish and Wildlife Service "Final Recovery Plan for the Sierra Nevada Bighorn Sheep" of Feb. 13, 2008 (at
http://ecos.fws.gov/docs/recovery_plan/080213.pdf)
From "ECOLOGY"
Leopold (1933) considered bighorn sheep to be a wilderness species because they fail to thrive in contact with urban development. Human disturbance has been suggested to be detrimental to bighorn sheep in a variety of situations (Graham 1980, MacArthur et al. 1982, Etchberger et al. 1989, Papouchis et al. 2001). Similarly, Dunaway (1971) postulated that disturbance of bighorn sheep in the Sierra Nevada by humans was a factor limiting populations.
Results of subsequent research did not support that hypothesis (Wehausen et al. 1977, Hicks and Elder 1979, Wehausen 1980). Bighorn sheep have habituated to human activity in many places in the Rocky Mountains, and occasionally in desert habitats. Any conclusions about the effects of human disturbance, however, must be limited to the situations studied. Thus, the question should be revisited as situations change in a direction that suggests disturbance could be detrimental, such as increased presence of humans in bighorn sheep habitat.
From "National Park Service ... Historical Management"
Following the lead of the U.S. Forest Service, Sequoia and Kings Canyon National Parks in the early 1970s closed “the female/lamb range of the Sierra Nevada bighorn sheep . . . to all pack animals and to off-trail travel by humans [in the national park].” This closure was later codified in the Superintendent’s Compendium. The associated map identified an area representing the known range of females and lambs within King Canyon National Park. Because off-trail travel by pack stock is impractical along the crest of the Sierra Nevada and the
occasional use by mountaineers and climbers does not pose a significant threat to bighorn sheep, and because the areas used by bighorn sheep will be in a state of flux for the indefinite future, the permanent closure was terminated in 2001.
from "OUTLINE OF RECOVERY ACTIONS"
Manage human use locally where it is found to cause bighorn sheep to avoid important habitat and thereby compromises survivorship or reproductive success. This action will take place only if research (see Task 6.4) results in a recommendation to limit human use in some areas;
at present there appear to be few locations where recreational disturbance has the potential to significantly affect bighorn sheep. Focused research on effects of human activities on bighorn sheep will determine whether any limitations on human use are required. If it is concluded that limitations will be beneficial, appropriate actions should be taken to limit human use that is found to be detrimental. Disturbance by humans (or possibly by off-trail domestic dogs) will be significant to bighorn sheep if nutrient intake of a herd is compromised by avoiding key foraging areas because of human activity. Both quality and quantity of forage vary greatly across the landscape, and bighorn sheep visit key locations where more nutritious forage is available. If bighorn sheep are regularly displaced from such areas and cannot procure equivalent nutrient intake at an alternative site, population parameters of the herd will be negatively affected. If they frequently flee encounters with humans, there may also be an unnecessary waste of energy that can have population-level effects.
From "Initiate or continue needed research."
Investigate and analyze human use patterns relative to habitat use patterns of bighorn sheep. Earlier investigations of hypotheses concerning human disturbance (Dunaway 1971) dismissed it as not important for the Mount Baxter herd, but possibly a factor for the Mount Williamson herd (Wehausen et al. 1977, Hicks and Elder 1979, Wehausen 1980). Bighorn sheep have been reintroduced to three additional areas since the earlier studies, but these new herds have not been investigated to determine the possible impacts of human disturbance. There is a need to investigate patterns of use by humans and domestic dogs including intensity, trends, and types of use in and near existing bighorn sheep habitat to identify areas of possible conflict. If areas of concern are identified, intensive studies to investigate whether human disturbance may be displacing bighorn sheep from favorable habitat can be initiated. Potential reintroduction sites also should be investigated to identify areas of possible conflict.
From "APPENDIX J COMMENTS RECEIVED ON THE DRAFT PLAN"
Comment: Some commenters were concerned that the study of human/recreational impacts, including impacts from dogs, is only a low priority.
Response: Actions to ameliorate the effects of human/recreational use were not given high priority in this plan because
we do not currently consider recreational use, including the activities of dogs, a significant threat to Sierra Nevada bighorn. If information indicating recreational use is having an effect on recovery becomes available, appropriate actions will be recommended.
Comment: One commenter was concerned that the plan indicates the potential need for future restrictions on recreational users, but fails to specify what those actions might be.
Response: The recovery plan states that any actions limiting recreational use will take place only if research results in a recommendation to limit human use in some areas.
At present, there appear to be few locations where recreational disturbance has the potential to significantly affect sheep. Because the research needed to address this issue has not been completed, it would be premature to speculate about these actions.
Comment: One commenter believed the potential effects of off-trail recreation and mountain climbing on new herds that have become established and proposed future herd ranges have not been adequately addressed in the plan.
Response:
Although we recognize the potential of recreation to impact bighorn sheep, these impacts seem to be minor. However, the recovery plan calls for continued monitoring of the compatibility between recreational use of bighorn sheep habitat and bighorn sheep recovery