Evaluation of measures to promote desert bighorn sheep highway permeability : U.S. Route 93.

PDFTech ReportFHWA-AZ-14-677SPR-000-1(175) 677WildlifeInterstate highwaysTraffic volumeFencesAnimal behaviorHabitat (Ecology)Wildlife crossingsGlobal Positioning SystemArizonaArizona. Dept. of Transportation. Research CenterGagnon, Jeffrey W.Dodd, Norris L.Sprague, Scott C.Loberger, ChadNelson, RobBoe, SusanSchweinsburg, Raymond E.Arizona. Game and Fish Dept. Research BranchUnited States. Federal Highway AdministrationUS Transportation CollectionThis study evaluated desert bighorn sheep\ue2\u20ac\u201chighway relationships from 2008 to 2010 along a 17\ue2\u20ac?mi stretch of U.S. Route 93(U.S. 93), in northwestern Arizona. Highway reconstruction between mileposts (MP) 2.3 and MP 17.0 was completed in October2010. The research objectives were to:\uef\u201a\ub7 Assess sheep movements, highway crossing patterns, distribution, and determine permeability.\uef\u201a\ub7 Investigate spatial and temporal patterns of sheep highway crossings and relationships to traffic volume.\uef\u201a\ub7 Investigate spatial and temporal sheep\ue2\u20ac?vehicle collision patterns.\uef\u201a\ub7 Assess the impact of highway reconstruction activities on sheep movements, habitat use, and permeability.\uef\u201a\ub7 Establish baseline data for pre\ue2\u20ac? and during\ue2\u20ac?reconstruction movements, highway crossing and passage rates, and sheepvehiclecollisions against which to conduct a sound post\ue2\u20ac?reconstruction assessment.Researchers instrumented 38 desert bighorn sheep (Ovis canadensis) with GPS collars. Sheep crossed the highway 340 times.U.S. 93 constituted a significant barrier to sheep passage, as passage rates averaged just 0.07 crossings/approach. Passage ratesvaried by season, with summer rates higher than winter and spring rates given that sheep exhibited increased tolerance to trafficduring summer when crossing U.S. 93 in pursuit of water. Sheep exhibited minimal response to consistently high traffic volumeencountered during the daytime hours when they were predominantly active