Context. Human activity in wildlands can influence wildlife populations by decreasing or degrading habitat, decreasing survival, or through displacement. For bighorn sheep (Ovis canadensis), some human activities are detrimental and may result in physiological stress, altered activity budgets, or habitat abandonment. From 1979 to 2000, human recreation increased over 300% in areas occupied by desert bighorn sheep (O. c.nelsoni) in south-eastern Utah. Concurrently, the population of desert bighorn sheep occupying the Potash Bighorn Sheep Management Unit of south-eastern Utah was in steep decline.

Aims. We investigated behavioural responses of desert bighorn sheep to different levels of human activity in this area from 2002 to 2003.

Methods. We divided the study population into two areas on the basis of the level of human use, i.e. low and high. We observed desert bighorn sheep at seven sites within these areas, including three with a high level of human use and four areas of a low level of human use.

Key results. Desert bighorn sheep spent significantly less time grazing and more time vigilant in areas of a high level of human use than in areas of a low level of human use.

Conclusions. Human recreational use of desert bighorn sheep habitat has the potential to negatively affect foraging by desert bighorn sheep.

Implications. We raise a cautionary flag because recreational use in bighorn sheep habitat near Moab, Utah, continues to increase and bighorn numbers continue to decline. When managers consider proposals to increase areas or trails for human recreation, they should incorporate ways to minimise impacts and reduce stressors to bighorn sheep.