Bighorn sheep inhabit alpine habitats and exhibit behavior patterns that are extremely rigid and ritualized, and essential to population persistence (Geist 1971). Studies suggest that bighorns do not adjust well to disruptions of these patterns; consequently anthropogenic (human) disturbance may contribute to population declines (Geist 1971, Krausman 1983, Krausman et al. 1995, Weidmann and Bleich 2014).
Bighorn sheep are highly sensitive to disturbance by hikers, particularly during spring and summer (Dunaway 1971, King 1985, Papouchis et al. 2001). Bighorns are also sensitive to vehicle disturbance, showing increased heart rates at close ranges to vehicles and roads (MacArthur 1979) and avoiding high use road corridors despite the availability of potential suitable habitat (Papouchis 2001). Bighorn sheep use of mineral licks by both individuals and groups is negatively affected by human and road-related disturbance (Keller and Bender 2007).
Bighorn sheep spend significantly less time grazing, more time scanning and congregate in smaller group sizes in areas of high human use (Sproat 2012). Rams are generally more sensitive to disturbance in autumn during the mating season, and females flee at greater distances in spring during lambing season (Papouchis 2001). Spring harassment can be particularly harmful to pregnant or lactating ewes in terms of energy costs, as rapid growth by lambs and lactation by ewes demand high amounts of energy (Moen 1981). Both fidelity to historic lambing areas and formation of nursery bands with exposed, precocial offspring, make bighorn sheep particularly vulnerable to disturbance near lambing areas (Beecham 2007), where moderate to high levels of human recreation activity may exclude bighorn females from their preferred habitat (Longshore et al 2013) during critical spring months (Thompson and Longshore 2007). Recreation and human presence near lambing sites may be detrimental to bighorn populations, leading to declines in recruitment and abundance (Graham 1980, MacArthur et al. 1982, Etchberger et al. 1989, Weidmann and Bleich 2014).
Bighorn sheep avoid winter backcountry recreation routes with both low and high intensity of use, even where they overlap with high quality winter habitat. Bighorn sheep are highly sensitive to human disturbance during winter and displacement from critical winter ranges and increase daily movement rates relative to recreation when resources are limited due to snow and cold temperatures (Courtenmach 2014, Jorgenson 1988, Legg 1998). This effective loss of winter habitat could potentially lead to less available forage, reduced productivity, density- dependence effects, and demographic consequences (Beale & Monaghan 2004). Off-trail, unpredictable human activity represents a disturbance to wintering sheep through a heightened perception of predation risk (Frid & Dill 2002).