Malaysian authorities are building more of the makeshift bridges after some orangutans were spotted using them over the past year, said Marc Ancrenaz, co-founder of French-based conservation group Hutan, which is working with Malaysian state wildlife department officials on orangutan protection.
Conservationists estimate about 11,000 orangutans live in Malaysia's Sabah state in Borneo, but many are isolated from each other because swaths of forest have been cut for development, logging and oil palm plantations.
Environmental groups and wildlife authorities have been hooking up old fire hoses strung together between trees on different sides of rivers to help orangutans - which cannot swim - swing or walk across them. The first bridge was set up seven years ago, but it was only last year that an orangutan was captured on camera using one of them.
Witnesses have seen others doing so since then, prompting officials to build more bridges.
"It takes a while for the animals to get used to it. ... If we are not able to reconnect them, they will go extinct very soon," Ancrenaz said.
But the bridges are "just a quick fix" because the long-term solution would be reforestation, Ancrenaz said.
Benoit Goossens, an adviser for the Sabah Wildlife Department, said more bridges will soon also be hung across oil palm plantation moats.
Studies of the orangutan population in part of Sabah indicated they might go extinct within 60 years due to inbreeding and loss of habitat unless the jungle patches are reconnected.
Hutan estimates the number of orangutans in Sabah has decreased eight-fold in the past 15 years, though conservation efforts in recent times have slowed the decline.
Last year, Sabah's government announced it would bar companies from planting palm oil and other crops near rivers to preserve the natural habitat of orangutans and other threatened animals. Authorities working with the World Wildlife Fund have also pledged to replant trees in crucial territory over the next five years.