Highways in the forest: How animals use canopy bridges

Walk through a rainforest and you’ll hear more than you see. Leaves rustle. Branches shake. Something is always on the move – but not on the ground.

Up in the forest canopy, life runs on its own network of bridges made of wood and leaves. Monkeys, sloths, and porcupines cross the treetops like commuters on morning routes.

That natural highway inspired scientists from Binghamton University to study how animals use man-made canopy bridges in the Amazon. Their work brings a fresh look at how treetop creatures behave and adapt in a forest that still feels untouched by humans.

Studying animal movement

At the Amazon Conservatory for Tropical Studies in Peru, researchers Justin Santiago and Lindsey Swierk set up cameras high in the forest.

The walkway they studied was built for scientists and visitors, stretching between 6 and 36 meters above the ground. It’s a web of ropes and wooden bridges connecting towering trees.

Four cameras ran for three weeks. Each one watched from a different height, day and night. The footage revealed sloths gripping bridge ropes, porcupines balancing on beams, and opossums darting across railings.

Most activity took place between 21 and 27 meters – right in the middle of the canopy. That’s where the temperature felt warm, the air stayed damp, and the wind softened. The animals seemed to prefer it.

When the forest sleeps

The cameras caught one clear pattern: the forest wakes up when the sun goes down. From 7 p.m. to 10 p.m., mammals crossed the bridges again and again. Some lingered longer, like the two-toed sloths, which stayed active until 4 a.m.

“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.

The timing makes sense. At night, the air cools and the forest grows still. Fewer humans walk the bridges. It becomes safer to travel and easier to hide.

The camera data showed higher humidity and warmer air during those hours – a comfortable mix for movement.

Rare species on canopy bridges

Among all the visitors, one stood out: the streaked dwarf porcupine, Coendou ichillus. Scientists call it data-deficient because so few sightings exist. Until recently, no one had recorded it alive in the wild. This study changed that.

The tiny porcupine appeared in the camera traps several times, moving carefully along the bridge ropes. Earlier research noted that C. ichillus usually stirs between 8 p.m. and 1 a.m. (exactly what the new footage confirmed).

Watching its behavior helped fill long-standing gaps in knowledge about this mysterious animal. For scientists, each appearance felt like a clue in an unfinished story.

Peak activity on canopy bridges

The middle canopy – roughly 21 to 27 meters high – was a sweet spot. Animals avoided the upper canopy, where the air turned hot and windy, and the lower levels, where predators might roam.

The mid-canopy provided cover and comfort. Here, animals could travel unseen and avoid risky gaps.

This preference matched patterns seen in other tropical forests. Activity peaks when conditions are mild, and most species favor hidden, stable routes over open, exposed paths. That behavior now shapes how scientists think about future bridge designs.

A model for conservation

Santiago and Swierk’s research offers more than a snapshot of nocturnal life. It gives conservationists a model for how animals might use artificial structures in damaged forests.

“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.

Forests across the tropics are breaking apart due to logging and roads. For animals that rarely touch the ground, those gaps are dangerous. Bridges – whether natural or man-made – become lifelines connecting populations.

Designing better canopy bridges

The study showed that walkway design matters. Height, temperature, and wind all shape animal behavior.

If a bridge mimics the mid-canopy environment – stable air, moderate light, close vegetation – animals are more likely to use it. Such data-driven design can turn artificial walkways into real conservation tools.

The researchers plan to expand the study to compare forests with different degrees of fragmentation. The goal is to understand whether animals use bridges the same way in damaged habitats as they do in pristine ones.

That knowledge could guide future wildlife corridors across South America’s shrinking forests.

A quiet connection

The Amazon canopy never sleeps. Even as people walk the bridges by day, animals claim them at night. Each crossing – by sloth, porcupine, or opossum – shows how life adapts when given the chance.

The study reminds us that simple human structures can sometimes reconnect what’s broken.

A walkway meant for visitors can also serve as a road for the forest’s original inhabitants. High above the ground, in the quiet dark, the rainforest keeps moving.

The study is published in the journal Neotropical Biology and Conservation.

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