Road culvert or wildlife crossings?: the hidden connectivity of terrestrial vertebrates under linear transport infrastructures

Abstract

Habitat fragmentation is one of the greatest threats to biodiversity. Linear transport infrastructures, such as roads, are one of the main causes of habitat fragmentation and may be corrected by wildlife crossings, although their implementation is still scarce. However, drainage culvert under linear transport infrastructures could indirectly act as wildlife crossings by increasing landscape connectivity.

Our aim is to identify which vertebrate species cross road drains in a protected area in Almería (SE Spain). For this purpose, camera traps were installed in 8 transversal drainage culverts during a complete year (2023-2024), analysing the crossing events by different vertebrate species as well as their spatial and temporal patterns.

The results showed that the drainage culverts can be used as wildlife crossings by vertebrate species of interest including mammals (e.g. Capra pyrenaica, Eliomys quercinus, Felis silvestris, Oryctolagus cuniculus) and reptiles (Testudo graeca, Timon nevadensis). An increase in vertebrate crossing rates was detected during the months of May-June and September-October. Most of the crossing events by mammals occurred at night, whereas those of ectotherms such as reptiles were detected during the day. We reported the first detections of T. graeca, an endangered reptile in Andalusia (Spain), crossing drainage culverts or non-wildlife crossing under a linear transport infrastructure in its whole distribution range. We conclude that in the absence of suitable and specific wildlife crossings, which need to be increasingly implemented in the short term, road culverts have great potential to improve the connectivity of vertebrate populations, including endangered species.