The highway of death: Snakes vs cars

Methods

Summary

This study will be conducted on a 79.9 km highway located on the eastern plains of Colombia, between the cities of Villavicencio and Puerto López, Meta department. This road was selected because it maintains high vehicular traffic that crosses one of the main ecosystems of the region: the savanna ecosystem. We selected 13 sampling points along the road with different degrees of landscape heterogeneity based on the proportions of four types of vegetation cover: pastures, gallery forests, crops and urbanized areas. Each point consists of a circle of 500 m radius starting from a central point on the road, and is separated from the nearest point by a minimum distance of 1500 meters. In order to survey snakes at these points, we will conduct six 13 day surveys in 2017: three during the dry season and three during the rainy season. To sample snakes at each point, five transects of 100 x 2 m will be established on each side of the road. These transects will be sampled during the morning and at night. Likewise, 1000 m on the road will be sampled during the dawn hours to detect individuals killed by vehicles. All individuals will be photographed and their total length will be measured. Additionally, corpses found on the road will be sexed using manual retraction of hemipenes or direct dissection, and will be preserved in formaldehyde for later identification (Castillo R et al., 2015). In order to establish the relationship between the ecology of a snake species and its roadkill rate, we will collect data on temperature, humidity and canopy cover in each of the sampling transects, as well as consider the foraging habits reported for the species in the literature. Species will be identified to the lowest taxonomic level possible.