Researchers were amazed to see, and capture footage of, red langur monkeys and white-bearded gibbons mobbing a predator in the rainforests of Borneo.
This extraordinary behaviour was particularly interesting as two groups of different primate species joined forces to harass the feline.
The field team from Borneo Nature Foundation (BNF) were observing wild red langur monkeys in the Sabangau Forest in Indonesia, as part of their long-term behaviour research project.
A nearby group of white-bearded gibbons started to give alarm calls towards an area of tangled vegetation in the forest canopy. The langurs joined the gibbon group and also directed alarm calls.
It turned out that there was a Sunda clouded leopard hiding in the canopy, who was bombarded by alarm calls for over two and half hours and even had its tail pulled by the male gibbon.
“It was very exciting to watch these wild animals come together and interact this way,” said J Zainuddin, a BNF field assistant and paper co-author.
“It is something I have never seen before. I think we were also very lucky to get this rare behaviour on camera.”
The BNF team have two theories as to why the cloud leopard was mobbed by the primates.
First, the leopard may have been sleeping when encountered by the gibbons, as it is normally a nocturnal species.
Secondly, an infant from the gibbon group had been missing for three weeks prior to this interaction and it may have been predated upon by the leopard.
Although the gibbons and langurs put themselves at risk by mobbing the leopard, it was beneficial for them to work together to deter this predator.