Effects of large-scale gold mining on migratory behavior of a large herbivore

Loss of migratory corridors has been identified as an important ecological issue among species that exhibit long-distance migration worldwide. Increased mineral exploration and development has raised the level of concern over the protection of terrestrial migration routes for ungulates. Mineral exploration and other types of development may adversely affect migratory corridors for large herbivores, but little is known about functional effects on migratory behavior and resource selection. To address these important questions we examined movement patterns and resource selection to understand the effects of an operating gold mine on migratory pathways of mule deer (Odocoileus hemionus). We captured and applied radio collars to female mule deer (n = 43) on the migratory pathway and in the proximity of an active mine in the Ruby Mountains of eastern Nevada. We used Brownian Bridge Movement Models to delineate stopover sites for each individual during both the autumn and spring migrations. We calculated linear efficiency of movement along the migration path and movement rate between stopover locations outside and within the mining area to determine the effects of the mine on movement patterns. We also used resource selection functions to determine if mule deer avoided areas with extensive excavation and disturbance of the land surface when navigating through the mine complex. Our results indicated greater linear efficiency of movement along the migration path and movement rates between stopover locations outside the mine when compared with movement through the mine complex. Additionally, mule deer that migrated through the mine complex avoided the highest disturbance levels by spending the majority of their time in undisturbed habitat patches. These results suggest an increase in energy expenditure of mule deer navigating through highly disturbed areas, which may have fitness consequences for migratory animals. Such increases in energy expenditure during migration may decrease survival or productivity of migratory populations of large, terrestrial mammals.