“We’ve been waiting years” for this moment. Sumatran orangutan used suspension bridge for the first time to cross road in Indonesia.
A surveillance camera installed in a forest in North Sumatra, Indonesia, recently recorded a moment considered historic for conservation: a Sumatran orangutan, whose species is critically endangered, crossed a public road for the first time using a suspension bridge built between the treetops.
The young male was filmed moving over a rope bridge installed above the Lagan-Pagindar road in Pakpak Bharat district. The road crosses an area of forest and, after works completed in 2023, began to separate two patches of habitat that were previously connected by the tree canopy, explains .
For human communities, the road represents an essential link to schools, hospitals and other services. But for orangutans and other arboreal species, it has become a dangerous barrier. The great primates spend more than 90% of their time in treeswhere they feed, rest, build nests and move. When a road opens a clearing that is too wide between the canopies, the forest no longer functions as a continuous territory.
The bridge in question is part of a set of five flyovers installed along the Lagan-Pagindar road to reduce the impacts of habitat fragmentation. Around 350 Sumatran orangutans live in this region, where a local population was divided in two because of the widening of the road.
What has now been released shows that the structure, despite being highly simple, can even function as an ecological corridor.
Forest fragmentation is now considered one of the biggest threats to the survival of orangutans. An area may continue to appear green on a map, but if it is cut off by roads, crops, or other infrastructure, it can turn into a succession of ecological “islands.” And for an animal that avoids moving on the ground, every opening is a huge risk. Why, on the ground, orangutans are more exposed to dogs, vehicles, hunters, people and open spaces that are unfamiliar to them.
After this separation, another problem arises: when animals on one side of the road stop crossing and reproducing with those on the other side, the population loses genetic diversity. In the long term, this isolation increases the risk of inbreeding and makes groups more vulnerable to disease, environmental changes or unexpected events.
The bridge now used by the orangutan is about ten meters long and suspended above the road. Each of the five structures installed in the project required about 200 meters of rope and was built in three to four days by a team of 12 people, according to sources.
Before the orangutan, the cameras had already registered other users. But no orangutans, plus squirrels, long-tailed macaques, Sumatran black langurs and agile gibbons. The use by an orangutan represents a new “light” on the project.
They were built in total three types of bridges: simple ropes, horizontal ladders and hybrid structures. The diversity of designs seeks to respond to the needs of different species, although the orangutan is the main focus.
The bridges have been safety tested and are part of a monitoring and maintenance program. Assessments of structures are carried out every three months and data is collected from surveillance cameras, and the Pakpak Bharat district government plans to install traffic signs before each bridge to warn drivers and encourage them to reduce speed. Local patrols are also planned, in conjunction with a forest management unit, to monitor the passages and deter hunters.
The Sumatran orangutan is critically endangered and survives only on the island of Sumatra. The other two species of orangutan — the Bornean orangutan and the Tapanuli orangutan — also face serious threats.
There are less than 14,000 Sumatran orangutans left in the wild, around 800 Tapanuli orangutans and approximately 104,700 Bornean orangutans. THE orangotango-de-tapanulilimited to a single forested area in North Sumatra, is considered the most endangered great ape in the world.
The conservation of these animals is also important for the health of tropical forests. Orangutans feed on fruits and disperse seeds, helping to regenerate the forest. That is why they are known as “gardeners of the forest”.
