Designing crossing structures for wildlife underneath roads is a challenge because species may respond differently to factors such as nearby habitat or crossing-structure dimensions. Here we show that large, open crossing structures along natural travel corridors accommodate the highest diversity of large and medium-sized mammals.

Nearly 9 million medium- and large-sized mammals (>1kg) could be killed on Brazilian roads each year, representing an estimated wildlife biomass of over 10,000 tons. Mortality from roads is a major threat to wildlife conservation in Brazil, and further research and mitigation is urgently needed to avoid species extinction.

The tiny Leadbeater’s possum is critically endangered from a combination of habitat destruction, timber harvesting, the effects of high-intensity forest fires, and habitat fragmentation from roads and fire-breaks. We tested two different designs of canopy bridges across roads in their forest habitat and both were used, reducing the risk of predation by terrestrial predators and wildlife-vehicle collision.

Mammal roadkill can negatively affect wildlife populations but exactly how it does so remains unclear. This study reviewed globally published studies to examine how roadkill affects populations.

A review of 1517 studies from around the world concludes that population-level studies are highly underrepresented and addressed road impacts on only 2% of threatened species. Most research was in developed nations, while developing countries are lagging behind.

We used a long-term citizen science data set of bat roadkill and found the rates of mortality were higher in protected areas than non-protected area at higher elevation in Taiwan. In contrast, roadkill of common bat species was best explained by high levels of light pollution at lower elevations, suggesting that bats might be exposed to higher collision risk when they were attracted by insects around streetlights.

Lighting in wildlife underpasses significantly reduces their use by bats. Bats are more likely to cross the road rather than use the underpasses when they are lit, greatly increasing their risk of mortality.

Water culverts along Autoroute 10 in Quebec are used considerably less than one would expect for designated wildlife passages for mammals, since out of 20 species present in the vicinity of the culverts, only about half of them were ever detected making a full crossing, and only two species highly tolerant to water crossed the structures on a regular basis (common raccoons and American mink). Water level and use of polyethylene as construction material were the strongest deterrents.