Publication

The availability of surface water is assumed by many wildlife managers to be important to desert bighorn sheep (Ovis canadensis nelsoni). Yet scientific evidence suggests bighorn sheep populations can sometimes fulfill their water requirements from forage alone. To investigate how water use changes with environmental conditions, we analyzed the surface water use and movement patterns of 4 desert bighorn populations across a range of meteorological conditions in the Mojave Desert in California, USA. We compared ground-based weather data to the daily use of surface water sources for 65 known individuals, and examined the movement patterns of 18 of these individuals with global positioning system collars in relation to visitation to surface water sources. Maximum daily temperature most closely predicted the percent of bighorn visiting water daily, with visitation increasing approximately 30% between 30 degrees C and 40 degrees C. Individual animals switched from a tortuous foraging movement to directed movement when accessing surface water. Day length, maximum daily temperature, minimum daily temperature, solar radiation, and the interaction between day length and minimum temperature explained the distance desert bighorn were located from the nearest water source. Our results indicate that local meteorological conditions are important determinants of desert bighorn surface water use, and that managers should monitor water sources when the maximum daily temperature exceeds 35 degrees C. Individual animals meet their water requirements with surface water under hot and dry conditions, likely because it is temporally or energetically efficient given their other resource needs.