Narrow bridges

Roads have shattered the habitat of an endangered monkey. Can bridges fix it?

At the top of the hill road leading to Penang National Park in Malaysia, cars and motorbikes drive through the forest at high speed. Some 40 feet above a particularly busy bend, almost invisible to the untrained observer, hangs an overhead bridge made of rope and recycled fire hoses. It’s easy to miss, but this humble crossing has the power to save lives.

Dusky langur lives, that is.

Why we wrote this

In the forests of Malaysia’s Penang and beyond, new crossings are helping people and wildlife coexist peacefully.

Once abundant on the Malay Peninsula, these endangered primates – also known as dusky leaf monkeys – have large white-rimmed eyes that make them look serious and bespectacled, and they’re essential to the local ecosystem. The Langur Project Penang, a citizen science project founded by wildlife researcher Jo Leen Yap, has seen thousands of animals safely cross the road using its bridge.

The aerial crossing – the first of its kind in Malaysia – is part of a global trend by conservationists to use bridges, tunnels and other passageways to combat habitat fragmentation caused by human development. “As we humans increasingly encroach on the natural world, we must also step up and take responsibility for the well-being of our wildlife,” says Allen Tan of the conservation group Habitat Penang Hill. “Jo Leen’s bridge is a big step in that direction.”

Teluk Bahang, Malaysia

At the top of the hill leading to Penang National Park in Malaysia, cars and motorbikes speed through the forest. Some 40 feet above a particularly busy bend, almost invisible to the untrained observer, hangs an overhead bridge made of rope and recycled fire hoses. It’s easy to miss, but this humble crossing has the power to save lives.

Dusky langur lives, that is.

Once abundant throughout Peninsular Malaysia, these endangered primates – also known as dusky leaf monkeys – have large white-rimmed eyes that make them look serious and bespectacled, and they’re essential to the local ecosystem . Their numbers are dwindling partly because of their own movements; dusky langurs travel between treetops leaping from branch to branch with complete abandon, but when tree cover is thin they resort to using power cables or scrambling across the ground, often resulting in electrocution and fatal collisions with motorists. The Langur Project Penang (LPP), a citizen science project founded by wildlife researcher Jo Leen Yap, counted seven road fatalities on this half-mile stretch of Teluk Bahang road before the construction of the bridge. Since then, thousands of animals have crossed the road without incident.

Why we wrote this

In the forests of Malaysia’s Penang and beyond, new crossings are helping people and wildlife coexist peacefully.

The aerial crossing – the first of its kind in Malaysia – is part of a global trend by conservationists to use bridges, tunnels and other passageways to combat habitat fragmentation caused by human development.

“As we humans increasingly encroach on the natural world, we must also step up and take responsibility for the wellbeing of our wildlife,” says Allen Tan, chief executive of The Habitat Penang Hill, a conservation of the tropical forest which rewarded the research. grants to Ms. Yap through her charitable foundation. “Jo Leen’s bridge is a big step in that direction.”

The love of languages

As a resident of Penang, Ms. Yap considers dusky langurs an important part of her natural heritage. Aside from its cute appearance, the shy species serves as an important seed disperser, helping to regenerate forests.

Courtesy of Langur Penang Project

Jo Leen Yap, the founder of the Langur Project Penang, on one of her many visits to the forest to study the behavior and habitats of the dusky leaf monkeys.

She founded LPP in 2016 with the goal of ensuring that future generations can see and appreciate dark langurs, just as she does. Its team of volunteers – mostly members of the local community and undergraduate students from Universiti Sains Malaysia, where Ms Yap is earning her doctorate. – focuses on research into dusky langur behavior, as well as public awareness and education. Locals are encouraged to report dusky langur sightings, including any signs of distress or traffic accidents, through LPP’s social media channels.

The group named their urban canopy bridge Ah Lai’s Crossing, after the first alpha male langur that LPP tracked for a long time. Ms Yap says it took months of patience to get closer to him. “Once he felt comfortable with me, he took me to his habitat and introduced me to his wife and children,” she says with a delighted laugh. “Thanks to Ah Lai, I was able to study several generations of this langur family.”

According to Ms. Yap, Ah Lai is now expanding her family to another forest. But its local legacy lives on at Ah Lai’s Crossing, which LPP built in February 2019 and reinforced in August 2020. The now double-layered bridge is made of discarded fire hoses collected and donated by the protection organization animals Ape Malaysia. Ms Yap says she chose the fire hoses because they “have great tensile strength and are easy to maintain”.

LPP’s camera trap captured over 2,100 traverses in its first two years. “It took the first dusky langur a few weeks to get used to the crossing, but when we saw it captured on camera, all the time and effort was worth it,” says Hoon Cheng Teo, a citizen volunteer. .

Besides dusky langurs, long-tailed macaques, black giant squirrels, civets, and other nocturnal rodents have all been spotted using Ah Lai’s Crossing.

The case of animal infrastructure

In designing Ah Lai’s Crossing, Ms Yap was inspired by similar projects around the world, such as the bamboo bridges for primates and slow lorises in Indonesia and the famous wildlife overpass in Canada’s Banff National Park. . More recent initiatives include a huge cougar bridge in Los Angeles and a beaver tunnel in Scotland. Studies in North America and Australia show there is also a significant benefit for humans, with wildlife crossings helping motorists avoid dangerous and costly collisions.

Courtesy of Langur Penang Project

A camera trap image shows a dusky leaf monkey crossing the road using the canopy bridge created by the Langur Penang project.

Margaret Lowman, or “Canopy Meg” as she is known, is a pioneer in canopy ecology. She says wildlife passages are absolutely essential to allow animals to roam freely and find new habitats when old ones are destroyed by humans, as is increasingly common, but they must be designed with the environment in mind. behavior of species. “Canopy crossings are probably the most effective for monkeys because they exist at treetop level where the animals already live. They provide continuity of movement where humans may have cut the tree canopy to clear space for construction,” she says.

Dr. Lowman adds that engineering animal canopy crossings is quite simple. Yet crossings come with challenges.

Ah Lai’s Crossing took months of patiently monitoring animal behavior, mapping the most critical crossing areas, obtaining government permits and fundraising. Ms Yap and her team are again working on research and permits in hopes of replicating this initiative elsewhere in Penang and beyond.

Seeing the success of Ah Lai’s Crossing, the Habitat Foundation is considering grants to help build LPP’s future bridges, Mr. Tan says. “Dark langurs are lovable, docile and charismatic creatures, and we need to do our best for them.”