Performance indices to identify attributes of highway crossing structures facilitating movement of large mammals

Published source details Clevenger A.P. & Waltho N. (2005) Performance indices to identify attributes of highway crossing structures facilitating movement of large mammals. Biodiversity and Conservation, 121, 453-464.
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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 1997–2000 in Alberta, Canada (Clevenger & Waltho 2005) found that large herbivores and carnivores used two wildlife overpasses. A total of 640 visits to overpasses by elk Cervus canadensis, 1,086 by deer Odocoileus spp., 10 by black bear Ursus americanus, nine by grizzly bear Ursus arctos, eight by wolf Canis lupus and 12 by cougar Puma concolor were recorded, with the majority involving animals crossing the structures. Features that positively influenced use of crossings (two overpasses and 11 underpasses) included increased width, height and openness. Black bears and cougars, though, favoured more constricted crossing structures. Increased length and noise negatively influenced use of crossing structures for some species. Two 50-m-wide overpasses were monitored along an 18-km-stretch of the four-lane Trans-Canada Highway. Barrier fencing, 2.4-m-high, ran alongside the highway. Tracks were monitored at each end of each overpass (in 2 × 4 m of sand/clay), every 3–4 days, from November 1997 to August 2000. Infra-red activated cameras were also used. Information about structure, landscape and human activity were recorded for each overpass.

(Summarised by: Alison Huyett )
Install barrier fencing and underpasses along roads

A study in 1997–2000 of a highway in Alberta, Canada (Clevenger & Waltho 2005) found that underpasses, in areas with roadside fencing, were used by large mammals. The 11 underpasses were visited by elk Cervus canadensis (1302 records), deer Odocoileus sp. (543), cougars Puma concolor (105), black bears Ursus americanus (103), wolves Canis lupus (43) and grizzly bears Ursus arctos (six). The majority of animals that visited underpasses crossed through the structures. Underpass height and width were both positively correlated with the number of animals using them. Two bridge underpasses (3 m high, 11 m wide), four concrete box underpasses (2.5 × 3.0 m) and five metal culverts (4 m high, 7 m wide) were monitored along an 18-km stretch of the four-lane Trans-Canada Highway. Barrier fencing, 2.4 m high, ran along the highway. Tracks were monitored at each end of each crossing, in a 2 × 4-m sand, silt and clay tracking station, every 3–4 days from November 1997 to August 2000. Information about each structure, the surrounding landscape, and human activity were recorded for each underpass.

(Summarised by: Rebecca K. Smith)