Zero roadkill as Amazon canopy bridges secure 15,000 crossings

From the article:

About 2,900 kilometers (1,800 miles) away, on the road that leads to Alta Floresta, a small Amazon town in the far north of Mato Grosso state, cases like the buffy-headed marmoset’s roadkill have not been recorded since 2024. That year, eight canopy bridges were installed, connecting fragmented forest patches. Camera trap footage revealed that, over 15 months, the aerial wildlife crossings enabled 15,000 safe crossings by arboreal animals — and not a single roadkill.

The bridges are part of a program involving Projeto Reconecta and the municipal government, along with local organizations and business owners who are eager to conserve the unique biodiversity of their town and promote ecotourism, but were alarmed by the growing number of wildlife-vehicle collisions.

Biologist Fernanda Abra, an associate researcher at the Smithsonian National Zoo and Conservation Biology Institute in the U.S., and the founder of Reconecta, recalled that just hours before installing the first bridges in Alta Floresta, she found two Schneider’s marmosets (Mico schneideri) dead. The species is endemic to the Brazilian Amazon and is threatened with extinction.

“A canopy bridge serves two purposes,” Abra said. “The first is to improve connectivity for wildlife, allowing animals to move from one side to the other in these fragmented forest areas. As a result, we also reduce roadkill.”

All bridges have two camera traps, one facing the crossing to record which animals are using it and another facing the forest to observe which animals arrive there but decide not to use it.

Among the primate species recorded using the bridges during the first months of the program were the black-faced black spider monkey (Ateles chamek), the Purus red howler monkey (Alouatta puruensis), the northern night monkey (Aotus infulatus), the tufted capuchin (Sapajus apella), Schneider’s marmoset and the Alta Floresta titi monkey (Plecturocebus grovesi).

Described only in 2019 and soon after classified as critically endangered, the Alta Floresta titi monkey has become the symbol of the initiative, which is now entering a new phase thanks to its positive results.

“In August, we will install eight more bridges in the city’s urban area,” Abra said. “The only difference is that the electric utility will first need to lower the power lines and insulate them so that if animals jump from the bridge onto the wires, they won’t be electrocuted.”

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The project underway in Alta Floresta is not Reconecta’s first. In 2021, working alongside the Waimiri-Atroari Indigenous people, the team installed 32 canopy bridges over BR-174, the highway that crosses both their territory and the Amazon between the Brazilian states of Amazonas and Roraima.

The Waimiri-Atroari helped Abra identify the best locations for the artificial bridges. Over the past five years, cameras mounted on the bridge poles have documented about 1,250 primate crossings, including the golden-handed tamarin (Saguinus midas), a species that is not strictly arboreal and often descends to the ground in search of food, making it particularly vulnerable to roadkill.

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After years of working along Brazilian highways, the biologist had always sought a solution that was simple, low-cost and durable. The current bridge features a multilayer design that accommodates primates with different modes of locomotion — from species that rely on their prehensile tails to move through the canopy to brachiating species such as spider monkeys, which swing using their arms, both of which are common in the Amazon, as well as species that simply walk across the network of crossed ropes. It is worth noting that other small terrestrial mammals, including opossums, sloths and mouse opossums, have also been recorded using the bridges.

Abra said it is important to keep in mind that this is a long-term project, and results are not always immediate. BR-174 was built in the 1970s, and animals take time to adapt to a new crossing alternative. Reconecta’s monitoring has shown that use of the structures increases over time.

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In Alta Floresta, tufted capuchins took seven months before using one of the bridges for the first time, which may indicate that each species has its own pace of adaptation.

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One of the hopes for reducing wildlife roadkill is the passage of a bill currently under consideration in Brazil’s Congress that would establish the National Road Safety Plan for Wildlife, which calls, among other measures, for the placement of wildlife warning signs, speed-reduction devices and the construction of overpasses, aerial crossings and underpasses along highways.

The bill has already been approved by the Chamber of Deputies and is now awaiting a vote in the Senate.

If approved, the canopy bridge model developed by Reconecta could be implemented nationwide. In 2026, Brazil’s National Department of Transport Infrastructure designated the design as the recommended standard for highways.

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Abra also hopes to bring her canopy bridges to other biomes, including the Pantanal and the Atlantic Forest, helping prevent the deaths of monkeys such as the buffy-headed marmoset.

Expectations are especially high for bridges over BR-262, one of Brazil’s longest highways, which cuts across the Pantanal and is known as the “highway of death.” The road kills approximately 2,000 animals every year.