The Influence of Land Use and Fences on Habitat Effectiveness, Movements and Distribution of Pronghorn in the Grasslands of North America
C. Cormack Gates, Paul Jones, Michael Suitor, Andrew Jakes, Mark S. Boyce, Kyran Kunkel and Kevin Wilson
Fencing for Conservation: Restriction of Evolutionary Potential or a Riposte to Threatening Processes? 277-294; 2012.
The pronghorn Antilocapra americana is an open-country grassland and shrub-steppe obligate and the sole surviving member of a taxonomic family unique to North America. Adapted to outrun American cheetahs, Miracinonyx trumani , an extinct predator that once roamed the North American plains (Byers 1997 ), the pronghorn can reach a top speed of nearly 100 km/h, making it the fastest land mammal on the continent. With its exceptionally large eyes set far back on the skull it can detect movements up to 5 km away, and with a burst of speed it can quickly deter any modern predator from giving chase. Despite these and other adaptations to the prairie landscape, the pronghorn is ill equipped to deal with the agro-industrial and social transformation of the mixed-grasslands of the Northern Great Plains, which began at the turn of the nineteenth century (O’Gara and McCabe 2004 ).
Today, the landscape mosaic of native prairie and cultivated fields comprising the northern mixed-grasslands largely reflects the early agricultural history of the region. More broadly, the prairies continue to be dramatically altered by the cumulative effects of cultivation, irrigation, roads, petroleum and natural gas development mining, water development, urban expansion and exurban development, electrical transmission lines, fences and other developments (Barrett and Vriend 1980; Czech et al. 2000 ; Forrest et al. 2004 ). In Saskatchewan and Alberta, only ~20 and ~40%, respectively, of native mixed-grasslands remain untilled (Gauthier and Wiken 2003 ). As development progressed following settlement for farming and the human population grew, roads associated with industry and rural access improvement increased. By the mid-1990s more than 90,000 km of highways, roads and natural gas well-site access trails existed in the Grassland Natural Region of Alberta (Alberta Environmental Protection 1997).
Although pronghorn can persist in low numbers in cultivated areas, they are most common in large open native rangelands where they are able to satisfy life history requirements, including migrating in response to landscape and regionalscale variations of forage availability in winter. Human activities from the period of agricultural settlement during the early years of the twentieth century to contemporary infrastructure and industrial uses of the landscape have had a profound effect on the distribution and abundance of pronghorn. Here, we review the historical depletion and partial recovery of pronghorn and the contemporary infl uence of fences, roads and other infrastructure and human activities on the spatial ecology of pronghorn. We comment on the importance of land-use planning and measures that can mitigate the negative impacts of land use, fences and roads on ecological cohesion of landscapes to sustain the pronghorn as a common species.