WILDFIRE AND DESERT BIGHORN SHEEP HABITAT, SANTA CATALINA MOUNTAINS, ARIZONA

Abstract

The desert bighorn sheep (Ovis canadensis mexicana) population in the Santa Catalina Mountains, Arizona, has declined since the 1920s and was virtually extirpated in the late 1990s. Urban development, human recreation, and changes in habitat conditions due to wildfire suppression have contributed to the decline. Wildfires in 2002 and 2003 burned approximately 46,701 ha in the Santa Catalina Mountains, including areas previously inhabited by desert bighorn sheep. Our objectives were to estimate the amount of potential and historical bighorn sheep habitat in the Santa Catalina Mountains and to determine if the fires improved habitat quality for bighorn sheep. We created a spatial habitat suitability model to estimate the amount of potential and historical habitat available for bighorn sheep in the Santa Catalina Mountains. We then used Burn Severity maps and the Normalized Difference Vegetation Index to examine the impact of recent wildfires on bighorn sheep habitat. We calculated 39,201 and 9,017 ha of potential and historical habitat of desert bighorn sheep, respectively. Historical bighorn sheep habitat in the western Santa Catalina Mountains declined 64% since 1989. Approximately 21% of potential habitat and 24% of historical bighorn sheep habitat were burned during the fires, most of which experienced low burn severity that was not high enough to remove vegetation that decreases habitat quality for desert bighorn sheep. Any consideration of translocation of desert bighorn sheep to the Santa Catalina Mountains should further assess the suitability of the areas identified as potential habitat.