Road mitigation is a demographic filter for grizzly bears

Published source details Ford A.T., Barrueto M. & Clevenger A.P. (2017) Road mitigation is a demographic filter for grizzly bears. Wildlife Society Bulletin, 41, 712-719.
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This study is summarised as evidence for the following.

	Action	Category
	Install overpasses over roads/railways Action Link
	Install barrier fencing and underpasses along roads Action Link

Install overpasses over roads/railways

A study in 1996–2014 of 18 overpasses and 19 culverts crossing a major highway in Alberta, Canada (Ford et al. 2017) found that overpasses were used by grizzly bears Ursus arctos, particularly in family groups. Over an 18-year period, grizzly bears used overpasses more often (241 crossings/structure) than they used culverts (122 crossings/structure). Over an eight-year period, bear family groups used overpasses more often (1.4 family groups/year/structure) than they used culverts (0.0–0.3 family groups/year/structure). In 1996–2006, 2-m-wide pads, were covered in sandy-loam soil to survey bear movements at 23 crossing structures. From 2008, remote cameras were installed at all crossing structures. As more crossing structures were built in the area, they were added to the survey, up to a maximum of 18 overpasses and 19 culverts. It is not clear when these structures were built.

(Summarised by: Phil Martin)
Install barrier fencing and underpasses along roads

A study in 1996–2014 of a major highway in Alberta, Canada (Ford et al. 2017) found that culverts, in areas with roadside fencing, were used as crossing points by grizzly bears Ursus arctos, but less often than were overpasses, especially by family groups. Over 18 years, grizzly bears used culverts less often (122 crossings/structure) than they used overpasses (241 crossings/structure). Over eight years, bear family groups used culverts less often (0.0–0.3 family groups/year/structure) than they used overpasses (1.4 family groups/year/structure). In 1996–2006, 2-m-wide pads, were covered in sandy-loam soil to survey bear movements at 23 crossing structures. From 2008 to 2014, remote cameras were installed at all crossing structures. As more crossing structures were built in the area, they were added to the survey, up to a maximum of 19 culverts and 18 overpasses. Crossing structure entrances were separated from the road by fencing.

(Summarised by: Phil Martin)