Long-term monitoring of wildlife crossings structures in the Atlantic Forest, Argentina

VARELA, DIEGO MARTÍN

Lavras

Congreso; First Ibero-American Congress on Biodiversity and Road Infraestructure; 2016

CBEE-UFLA

The current increase of transport infrastructure in Latin America represents a serious threat to habitats and species in biodiversity hotspots. Nowadays, new roads break through protected areas and biological corridors, and old dirt roads are being paved, thus decreasing ecological connectivity and increasing wildlife road-kills. The subtropical forests of north-eastern Argentina (Misiones Province) are considered one of the major and best connected remnants of the whole Atlantic Forest eco-region, sustaining healthy populations of large mammals. However, increasing of paved roads in Misiones is affecting threatened species as jaguars and tapirs. Wildlife crossing structures are uncommon in Latin America and there are only few known cases of mitigation measures designed to minimize the impact of roads on Neotropical wildlife. During the last years, the Road Administration of the Misiones Province showed an increasing commitment about wildlife issues undertaking the construction of the first wildlife passages (underpasses) of Argentina and the first wildlife overpass (ecoduct) of Latin America. The aim of this study was to evaluate long-term performance of seven wildlife passages located on two roads (RP-19 and RN-101) within and around Urugua-í Provincial Park (84,000 ha). The RP-19 cross through the park and have four small underpasses without streams (three 2m wide x 2m height, and one 4m w x 2m h) built 22 years ago, whereas RN-101 border the park and have two medium-sized underpasses (4m w x 3.5 h, 5.5m w x 3.5 h) and one wildlife overpass (40 m width) built in 2008. Wildlife passages were monitored by camera traps (Reconyx RC60OH) to record large- and medium-sized mammals use. All cameras operated 24h per day. The overpass was monitored for five years (2011-2015) and underpasses for four years (2012-2015). Total sampling effort was 4,740 camera-days. To ensure independence, consecutive photographs of the same species within one hour were excluded. Wildlife Crossing Use Index (WCUI) was defined as the ratio between independent crossing events and sampling effort (camera-days). Till now, 28 species of large- and medium-sized mammals were recorded in the seven wildlife crossings. This represents about 80% of all species potentially present in the region. Tapir, Brazilian Dwarf Brocket, Red Brocket, Collared Peccary, Paca, Puma, Ocelot, and Oncilla were recorded, among others species. The WCUI in the oldest underpasses of RP-19 were more than tenfold greater that in RN-101 underpasses. However, only the wildlife crossings of RN-101 (over- and under-passes) showed an increase in WCUI and in the number of species recorded across years, revealing a process of progressive species adaptation to the structures after its construction. In last years, some underpasses of RP-19 showed a decrease in WCUI possibly due to management problems, such as excessive water accumulation or anthropogenic disturbances (road maintenance works). The flooding of passages affects medium-sized mammals, mainly carnivores. Twenty-five of the 28 mammal species registered to date utilized the RN101?s group of 3 passages (ecoducto and underpasses). Instead, only 19 species used the group of 4 underpasses in the RP19. However, these ones were used at higher rates by 4 ungulate species, including tapirs. These results indicate that wildlife crossings provide safe passage for Neotropical mammals on roads of Misiones. Nonetheless, species like jaguars and white-lipped peccaries were not recorded using wildlife crossings yet. Long-term monitoring will allow a better understanding of species adaptation to these structures and will lead to better planning of mitigation measures for Latin American roads.