Mitigating roadway impacts to migratory mule deer—A case study with underpasses and continuous fencing

Published source details Sawyer H., Lebeau C. & Hart T. (2012) Mitigating roadway impacts to migratory mule deer—A case study with underpasses and continuous fencing. Wildlife Society Bulletin, 36, 492-498.
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This study is summarised as evidence for the following.

	Action	Category
	Install barrier fencing and underpasses along roads Action Link

Install barrier fencing and underpasses along roads

A before-and-after study in 1990–2011 of scrubland in Wyoming, USA (Sawyer et al. 2012) found that underpasses beneath a highway, in areas with roadside game-proof fencing, were extensively used by mule deer Odocoileus hemionus and collisions between deer and vehicles reduced. Over three years, 49,146 mule deer were recorded moving through seven underpasses. Passage rates through underpasses of deer approaching to ≤50 m increased over three years, from 54% to 92%. After underpass construction, there were 1.8 collisions/month between deer and vehicles compared to 9.8 collisions/month before. Underpasses were also used by elk Cervus canadensis (1,953 crossings), pronghorns Antilocapra americana (201), coyotes Canus latrans (13), bobcats Lynx rufus (77), badgers Taxidea taxus (9), moose Alces alces (13), raccoons Procyon lotor (3) and cougars Puma concolor (1). Seven concrete underpasses (approximately 6 m wide, 3 m high and 18 m long) and 21 km of fencing were installed in 2001–2008. Three camera traps/underpass were operated from 1 October (16 December in first year) to 31 May between 2008–2009 and 2010–2011. Vehicle-deer collision data were collated before (1 January 1990–1 October 2001) and after underpass construction (1 October 2008–1 May 2011).

(Summarised by: Nick Littlewood)