Mammal use of underpasses to cross Route 606 in Guacimal, Costa Rica

Roads severely affect the health of ecosystems across the globe by fragmenting and diminishing habitats, reducing population connectivity, and increasing animal mortality. Wildlife underpasses allow for increased road permeability–the ability for animals to safely cross the road. Despite growing success in other regions, little is known about underpass usage in Central America. In this study, I monitored two dry circular culverts and two unfenced tunnels with barbed wire partially blocking their entrances on Route 606 in Guacimal, Costa Rica, from 14 November to 6 December 2021 using 15 camera traps to assess which species used them to cross. Twelve species used the culverts and tunnels for a total of 108 individual crossings. The tunnels were used, in descending order, by agouti (Dasyprocta punctata), common opossum (Didelphis marsupialis), dog (Canis familiaris), nine-banded armadillo (Dasyous novemcinctus), cat (Felis catus), Norway rat (Rattus norvegicus), ocelot (Leopardus pardalis), squirrel (Sciurus variegatoides), northern tamandua (Tamandua mexicana), and coati (Nasua narica). The circular tunnel, Tunnel 1, was used more frequently and by a greater diversity of species than observed in the square tunnel, Tunnel 2. The two smaller culverts were used by common opossum (Didelphis marsupialis), cat (Felis catus), rat opossum (Micoureus alstoni), and Watson’s climbing rat (Tylomus watsoni). Culvert 2 was used more frequently; however, Culvert 1 was used by a greater diversity of species. This study highlights wildlife underpasses as a critical strategy for biological conservation in Costa Rica through improved road safety and habitat connectivity