Paris - The orangutan population on the island of Borneo has shrunk by a quarter in the last decade, researchers say, urging a rethink of strategies to protect the critically-endangered great ape.
The first-ever analysis of long-term orangutan population trends revealed a worrying decline, they said.
An international team of researchers used a combination of helicopter and ground surveys, interviews with local communities and modelling techniques to draw a picture of change over the past ten years.
Previous counts have largely relied on estimations based on ground and aerial surveys of orangutan nests. Some suggested that Bornean orangutan numbers were in fact increasing.
Conflict with humans
The new findings, the team said in a statement, are "a wake-up call for the orangutan conservation community and the Indonesian and Malaysian governments who have committed to saving the species."
Every year, between $30-40m is spent in the region to halt wildlife decline.
"The study shows that these funds are not effectively spent," said the team.
The biggest threat to orangutans, one of only two great ape species found in Asia today, are habitat loss due to farming and climate change and their killing for food or in conflict with humans.
Some 2 500 orangutans are killed in Borneo every year, the researchers said.