Road-Killed Wildlife Carcass Frequency by Mile of Idaho State Highway System Routes in the U.S. Northern Rockies (2008-2012)

This layer represents 5-year relative counts of wildlife carcasses collected by Idaho Transportation Department (ITD) personnel (2008-2012) or reported by the general public (2012) on or adjacent to state highway system (major) routes. To obtain relative counts, the 5-year total counts per mile, which included all wildlife species observed, were divided by the maximum observed calue (98) to give a relative 0-1 risk score. Total counts, which include all wildlife species observed, along with carnivore counts, which include only black bears, grizzly bears, mountain lions, and wolves, are provided. Counts were derived by identifying the nearest mile marker to each carcass point location, then counting the frequency with which each mile marker was identified. Idaho Department of Fish and Game (IDFG) staff indicated that Idaho carcass data are expected to be underreported compared to Montana. Citizen reporting of wildlife carcass data beginning in 2012 may also introduce inaccuracies and further inconsistencies between Idaho and Montana. Thus, this carcass frequency layer is intended only for exploration of patterns in reported wildlife road mortality, not for formal statistical inference.The carcass dataset was screened to remove duplicate records, records for which the recorded species was not a wildlife species of interest (“Unknown”, domestic animals, or obvious errors), records for which no precise location information was available, and records falling >100m from state highway system routes.