Does the shape of the road influences wildlife roadkills? Evidence from a highway in Central Andes of Colombia

The highway infrastructures are a source of multiple environmental problems; one of the worst effects on wildlife is roadkill. Most of the research on roadkill has focused on how certain aspects, such as seasons, traffic density, and location of roadways, among others affect wildlife mortality on roads. However, little attention has been paid to understanding how the geometric design of roads affects wildlife mortality. On a highway in the Central Andes of Colombia, we investigated if the geometric design, specifically horizontal alignment and vertical curves of the road, influence the mortality of vertebrate animals on roadways. We determined the number of the straight lines, circular, transition curves, and vertical convex curves along the entire route of the highway (13.9 km), and from April 2018 to December 2019, we made 336 surveys in search of wildlife roadkill. We then investigated the relation of animal deaths to different road shapes. Out of 95 roadkill, reptile deaths made up 47% of the total. We found no dependence on the distribution of deaths by class of animals on the road shape; the shape in which most deaths occurred was a straight line (58 deaths). However, when the proportion of mortality events per meter was analysed on the shape units on the road, we found that circular and transition curves presented two and three times (respectively) a higher proportion of mortality events per meter than the straight lines. Roadkill hotspots were found in curved segments and were not associated only with riparian forest. The curved sections present more dangerous geometric designs than the straight lines for wildlife, regardless of their length on the road. Our research indicates that the relationship of the geometric design of roads needs to be considered in the development of management and conservation plans of altered ecosystems with the road infrastructure.