Seasonal Distribution and Routes of Pronghorn in the Northern Great Basin

Pronghorn (Antilocapra americana) exhibit complex spatial and temporal variation in seasonal movements and range use across their distribution. However, knowledge of seasonal movements, routes, and distribution of pronghorn within the sagebrush-steppe of the northern Great Basin is lacking. From October 2011 to October 2013, I monitored movements of adult female pronghorn across an area of over 1.5 million hectares along the northwestern Nevada and southeastern Oregon border using GPS/VHF-equipped collars. I used 68,834 GPS locations from 32 female pronghorn to determine migration timing, seasonal distributions, individual fidelity to winter and summer ranges, and population-level routes used during the migration period. Collared pronghorn were conditionally migratory, with 65% migrating an average of 30.0 km the first year and 100% migrating an average of 39.1 km the second; one individual migrated over 160 km between summer and winter ranges. Seasonal ranges averaged 143.3 km² during the summer, and from 252.9 to 459.9 km² during the winter (2010/2011 and 2011/2012, respectively). Individual pronghorn demonstrated wide variation in directional movement between summer and winter ranges, and there was high overlap of common areas across seasons and time periods. Pronghorn showed stronger fidelity to summer ranges than to winter ranges, and occupied higher elevations during the summer months, descending to lower elevations during the winter. Deeper snow and colder temperatures in 2012/2013 compared to 2011/2012 corresponded to longer average migration distances, fewer exploratory movements, larger winter ranges, lower elevational use, and a shift in winter range location. Habitat conversion, degradation, and fragmentation have accumulated across the sagebrush-steppe biome and are negatively affecting the long-term persistence of dependent wildlife. Applying knowledge of important seasonal use areas and routes used during migration in future conservation planning can mitigate impacts to pronghorn habitat and provide for long-term conservation.