IENE 2016

Large overpasses, called ecoducts or green bridges, are considered one of the best options for providing ecological connections across linear transport infrastructures. In Catalonia (NE Spain), several ecoducts have been constructed over roads and railways. Two of them (155 and 86 m wide) were built over the newly fenced C-37 road, which opened in 2009 in a mountain forest area. A monitoring project was undertaken from November 2014 to July 2015, to determine which species of invertebrates and vertebrates used the structures and their surroundings. Different monitoring techniques were applied, including invertebrate and small mammal traps, photo and video cameras, bird censuses and bat detectors. This presentation focuses on invertebrates and bats, which are often excluded from monitoring of wildlife passages. Invertebrates were captured in the ground layer in a network of 27 sample points. Entomology nets were used to capture animals found in the herbaceous vegetation and bushes. The taxa determination was undertaken with the help of binocular equipment (an in-depth study of the samples is still underway). Bats were detected by two bat detectors (Song Meter SM3, Wildlife Acoustics), equipped with SMX-US microphones. Two detectors were activated simultaneously from 21 to 24 h on 22 consecutive nights in the spring. Species were identified using SonoBat V.3.3.1 and Avisoft-SASLab Pro V.5.2.01 software. The number of records was counted, and the species were determined when possible, as some species cannot be differentiated by ultrasound registration.

A total of 179 invertebrate taxa were identified: 45 in the ground soil and 134 in the vegetation. The most abundant and diverse groups were Heteroptera, Homoptera, Orthoptera and Coleoptera in the vegetation; and Hymenoptera, Arachnida and Diplopoda in the ground layer. A total of 2,775 bat records were obtained, of which 94% were registered over the ecoduct, and the remaining 6% in the surroundings. Most records were of moving bats (95%), 3.7% were hunting, and 1% were engaged in social activity. At least 11 species were identified using the ecoduct: Rhinolophus ferrumequinum, Rhinolophus hipposideros, Myotis myotis/blythii, Myotis emarginatus,  Myotis daubentonii/capaccinii, Pipistrellus pipistrellus, Pipistrellus kuhlii/nathusii, Pipistrellus pygmaeus/Miniopterus schreibersii, Hypsugo savii, Nyctalus leisleri/Eptesicus serotinus, Barbastella barbastellus and Tadarida teniotis. The taxa most frequently detected were Pipistrellus kuhlii/nathusii (1305 records over the ecoduct, 90 in the surroundings) and Nyctalus leisleri/Eptesicus serotinus (614 records over the ecoduct, and 26 in the surroundings). These results suggest the existence of a funnel effect guiding bats’ flight across the structure.

The proper restoration of ecoducts and optimal connection with habitats each side of the structure are considered key to the successful results that were obtained. The results suggest that ecoducts play an important role in biodiversity conservation, as they not only provide a crossing point for medium and large mammals, as established in many monitoring projects, but also funnel bats’ flight and even provide habitats for a high diversity of small fauna. Therefore, ecoducts should be considered as important elements in the green infrastructure networks.