Surface Mining and Ecology of Desert Bighorn Sheep

Abstract

Understanding how mining operations influence use of habitat and movements by bighorn sheep (Ovis canadensis) is critical to long-term management of populations that inhabit areas in and around mining operations. We studied responses of a population of desert bighorn sheep to a surface-mining operation in the Silver Bell Mountains, Pima County, Arizona. We incorporated two study periods with different levels of activity at the mine: closure (1993–1995) and operation (2003–2005). We captured and radiocollared ≥22 bighorn sheep in each period and monitored size of home ranges, size of core areas, and use of the mine. Home ranges and core areas of adult males during the breeding season were larger during closure than during operation. During the non-breeding season, there was evidence that home ranges of adult males were larger during closure compared to when the mine was in operation. Core areas of adult males were similar in size during the non-breeding season of both periods. During the breeding season, adult males used the mine more while the mine was in operation than during closure. During the non-breeding season, however, adult males did not use the mine more during either period. Home ranges and core areas of females were not different in size during both seasons and periods of closure and operation of the mine. During both seasons, females used the mine more during operation than during closure. Overall, the population of desert bighorn sheep used an active mine more than it did when the mine was closed.