This layer represents 5-year relative counts of wildlife carcasses collected by Montana Department of Transportation (MDT) maintenance personnel or U.S. Fish & Wildlife Service Grizzly Bear Recovery Team personnel on or adjacent to on-system (major) routes from 2008 to 2012. 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. MDT states that “The MDT Carcass Database contains information on carcasses collected by MDT maintenance personnel; however, not all carcass collection is reported consistently or on a regular schedule. This makes the information provided by the Carcass Database useful for pattern identification over space and time, but not statistically valid.” 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 species was recorded as “Unknown”, and records located >100m from MDT on-system routes.