Linear infrastructure in the form of roads is a major source of habitat fragmentation and a barrier effect when animals cannot cross from one side to the other. Roads are a significant threat to tropical forest in Amazonia, fragmenting habitat for both terrestrial and arboreal species, with the latter at even more pronounced threat due to their need of canopy connectivity to move. Wildlife crossings structures have gained acceptance as mitigation measures and a few experiments to test use of different designs have been proved due the distinct locomotion in arboreal species.
We studied 10 paired canopy bridges of three designs and monitored them with camera traps between August and December 2021 in Tahuamanu, Madre de Dios, Peru. The bridges were 15 -35m±5. long and installed over a logging road, with two designs being two-dimensional and the third being unidimensional. Cameras were installed in bridges upon installation to register crossings in the canopy and beneath bridges on the ground to register ground crossings of arboreal mammals.
In 614 trap nights we logged 49 photo events only in one of the two-dimensional bridge designs and all of them were kinkajou (Potos flavus), with the first event being four days after installation. We conservatively estimate that these events represent four different individuals, and interestingly, the animals used only one side of the bridge to cross and crossing speed increased over time. However, on the ground, we recorded 51 photo events of five arboreal species (Ateles chamek, Sapajus macrocephalus, Saimiri boliviensis, Saguinus fuscicollis, Tamandua tetradactyla) crossing the road. Other studies in the area suggest that there are an additional ~ 20 arboreal species in the area. Our results provide valuable preliminary insights into habituation time and design preference for arboreal mammals in tropical forest. As our study continues, we will have more robust data to inform future canopy bridge projects and to contribute to this vital solution for arboreal mammals in a rapidly changing world.
Artificial canopy bridges, arboreal mammals, roads, logging, fragmentation, tropical forest.