Badgers and highways just don’t seem to mix.
Highway mortality has been shown to be the most significant source of loss in badger populations in the Thompson Valley. In this area, almost half of the radio-tagged badgers monitored in a recent study died while trying to cross highways or railways; 46% (6 of 13) badgers radio-tagged from 1999-2002 were killed on highways (Weir et al. 2003). An additional 13 untagged badgers were reported road-killed during this period and numerous reports of narrow escapes also exist. Highway mortalities do not appear to be age related; both adults and young have been killed (Weir and Hoodicoff 2002). Considering that the population of badgers in this region is estimated to be between 30 and 50 animals, this source of mortality likely has severe implications for population persistence. In fact, the National Recovery Strategy for the North American Badger, jeffersonii subspecies has listed “reducing highway mortality”, as a primary short-term recovery objective.
Why are badgers at such high risk for roadkill?
The difficulty that badgers face is that their home ranges, while mostly based in grassland habitats, are very large and often straddle major transportation corridors. In their normal day-to-day movements throughout their 20 – 50 km² home ranges, they are forced to cross these roads and railways, which pose a major mortality risk to the individual badgers. The following graphic shows the locations of 17 documented road mortality of badgers in the Thompson region between 1998 and 2002. The most concerning stretch of road is the TransCanada Highway between Lafarge exit and Pritchard. No fewer than 7 badgers were killed on this section of road between 1999 and 2003, including a female that had recently given birth to a kit. Road mortality is at its highest during July, when road traffic peak and male badgers are searching widely for mates.
Concrete road barriers (CRB’s) may be a significant factor in badger highway mortality. Numerous reports have documented badgers running down the roadside trying to exit the highway surface and unable to do so because of the high concrete barriers (Weir and Hoodicoff 2002). Whereas badgers are capable of climbing barriers, their natural instincts when threatened are to dig, which they cannot do on paved roads. Allowing badgers to exit the road surface through holes in the CRB may be one way to help reduce road mortality.
Badger Highway Mitigation Project
With funding from Habitat Conservation Trust Fund, the Province of BC has started a project to hopefully reduce the roadkill of badgers in the Thompson region. The primary objective of this project is to replace concrete road barriers in selected sections of highway in the Thompson Valley with permeable road barriers. Working with Argo Road Maintenance (Thompson), we have replaced 4 barriers along one 2 km long stretch of solid barrier on the TransCanada highway (photos below). The replacement barriers have openings in the bottom that are large enough for badgers to exit the highway surface. We hope to continue to monitor the effectiveness of this approach in reducing badger mortalities through continued monitoring of these replacement sites. The desired outcome of the project is to reduce highway mortality rates for badgers in this region. Reducing highway mortality by as much as 50% of the reported figures represents a total of 7% of the current provincial population estimate. We thank Argo Road Maintenance for their assistance and cooperation with this project.