Arboreal wildlife bridges in the tropical rainforest of Costa Rica’s Osa Peninsula

Abstract

Linear infrastructures, especially roads, affect the integrity of natural habitats worldwide. Roads act as a barrier to animal movement, cause mortality, decrease gene flow and increase the probability of local extinctions, particularly for arboreal species. Arboreal wildlife bridges increase connectivity of fragmented forests by allowing wildlife to safely traverse roads. However, the majority of studies about such infrastructure are from Australia, while information on lowland tropical rainforest systems in Meso and South America remains sparse. To better facilitate potential movement between forest areas for the arboreal wildlife community of Costa Rica’s Osa Peninsula, we installed and monitored the early use of 12 arboreal wildlife bridges of three different designs (single rope, double rope, and ladder bridges). We show that during the first 6 months of monitoring via camera traps, 7 of the 12 bridges were used, and all bridge designs experienced wildlife activity (mammals crossing and birds perching). A total of 5 mammal species crossing and 3 bird species perching were observed. In addition to preliminary results of wildlife usage, we also provide technical information on the bridge site selection process, bridge construction steps, installation time, and overall associated costs of each design. Finally, we highlight aspects to be tested in the future, including additional bridge designs, monitoring approaches, and the use of wildlife attractants.

A new window into canopy bridges as a mitigation strategy for arboreal mammals

“…The contributions in this special issue demonstrate the advances that researchers have made in understanding bridge use by employing camera traps for monitoring rather than traditional observation (Azofeifa Rojas and Gregory, 2022; Flatt et al, 2022;Hidalgo-Mihart et al, 2022;Minato et al, 2022;Monticelli et al, 2022;Yap et al, 2022). Furthermore, with the study by Franceschi and colleagues (2022), we also learned about effective arboreal application of a traditionally terrestrial method for monitoring bridges -a sand trap bed used to monitor a bridge -when camera trap theft is a concern.…”

“…Researchers also have had perhaps a surprising amount of success with simple single-line designs (fig. 2a 2022) or designs with two lines next to each other (Flatt et al, 2022;Prasetyo et al, 2022). Two studies of dormice on opposite sides of the globe had success with three-dimensional bridges, including triangular, quadrangular, and spherical designs (fig.…”

“…When installing canopy bridges, cost and maintenance can be a big concern and even inhibitory for implementation. Several papers in the special issue provide valuable information on the cost of the canopy bridges studied (Azofeifa Rojas and Gregory, 2022;Cunneyworth et al, 2022;Flatt et al, 2022;Minato et al, 2022). Azofeifa Rojas and Gregory (2022) also provide information on the maintenance schedule used to keep bridges functional.…”

“…Perhaps of most interest to the progress of canopy bridge science were studies that took an experimental approach to comparing different bridges (Flatt et al, 2022;Moffat et al, 2022;Narváez-Rivera and Lindshield, 2022;Prasetyo et al, 2022;Saralamba et al, 2022). Also worth highlighting is the fact that some species seem to be more amenable to using bridges, including howler monkeys, Alouatta spp.…”

“…While the special issue includes no contributions from Australia, it establishes that the number of canopy bridge studies in Brazil is steadily growing (Buss et al, 2022;Franceschi et al, 2022;Monticelli et al, 2022;Teixeira et al, 2022), with a review paper indicating that the country has nearly 150 canopy bridges (Teixeira et al, 2022). Research from Costa Rica is also well-represented in this special issue (Azofeifa Rojas and Gregory, 2022;Fan and Lindshield, 2022;Flatt et al, 2022;Narváez-Rivera and Lindshield, 2022), and while some countries have required linear infrastructure projects to include canopy bridges (e.g., Australia, Peru), remarkably, Costa Rica seems to be the first country in the process of passing legislation requiring canopy bridges over all new roads nation-wide (Azofeifa Rojas and Gregory, 2022).…”