Look up in the woods and you may see a familiar sight: squirrels using tree limbs like a leafy highway, crossing a patch of land without putting their paws on the ground.
That's true in the Amazon rainforest as well. A new study published by Binghamton University biologists in the journal Neotropical Biology and Conservation offers insights for the first time into how arboreal species use human-made canopy structures.
Authored by environmental studies alumnus Justin Santiago '21, now in a master's program at Miami University, and Binghamton University Assistant Professor of Biological Sciences Lindsey Swierk, "Arboreal mammal use of canopy walkway bridges on an Amazonian forest with continuous canopy cover" focuses on research conducted at the Amazon Conservatory for Tropical Studies (ACTS) Field Station in the Napo-Sucusari Biological Reserve, located 40 miles outside of Iquitos, Peru.
Either naturally occurring or artificially constructed, canopy bridges are exactly what they sound like: pathways that connect trees, offering passage to tree-dwelling animals. For example, think of a tree limb extending toward another tree in the woods, Santiago and Swierk explained. Artificial bridges may mimic these natural crossings or may take the form of an elevated walkway, such as the one used in their study. Whatever form they take, canopy bridges can be found all over the world - including in your own backyard.
The walkway at the ACTS Field Station consists of a series of platforms and bridges from 6 to 36 meters above the forest floor built primarily for use by researchers and visitors. Humans aren't the only tree-loving mammals to use such structures. According to the World Wildlife Fund, 427 species of mammals live in the Amazon; researchers estimate that 227 of these species spend a great deal of their time in trees.
The researchers set up four camera traps to record animals using the bridge over a three-week period; arboreal mammals were recorded using the bridge on 41 occasions. They included sloths, porcupines, opossums, monkeys and others.
During the survey, the animals used the bridge solely at night. While many species may have a nocturnal bent, others may be reacting to the presence of human beings using that same bridge for tourism. Outside of the survey period, a sloth and a troop of saki monkeys were seen using the walkway during the day, during a period of minimum human activity after the end of tourist season.
"Arboreal mammals are known to be shy and camouflage relatively well within their surroundings, yet at nighttime they have been shown to increase their activity and become much more mobile," Santiago said.
Future studies could address seasonal differences in canopy usage or explore potential changes in reported species.
Overall, their findings could aid in the development of future artificial canopy walkway designs. As forest habitats become fragmented, walkways provide a way for forest creatures to meet their survival needs while staying safe.
"In a broader context, as fragmentation continues to disconnect ecosystems, artificial canopy structures provide a safer route for arboreal species, keeping them away from roads where mortality events could occur," Santiago said.
