A strange monkey was observed in the forest along the Kinabatangan River in Sabah, Malaysia. The image of the monkey, after being posted on wildlife groups on social media, has attracted attention because of its appearance, the Guardian reported on June 12.

The scientists studied various photographs of the monkey, looking at its color and body detail, and concluded that it was likely a hybrid of a male proboscis monkey (Nasalis larvatus) and a female silver langur (Trachypithecus cristatus).

They observed that the mysterious monkey’s face was more like a proboscis monkey than a silver langur, although its nose was not as long as that of a proboscis monkey and its skin was gray. Its coat color distribution is characteristic of proboscis monkeys.

The hair of the strange monkey is long and dense, like that of a silver langur, but the sides of the face do not have a mane as is common in this species.

The putative hybrid monkey was first seen in 2017, and is now an adult. It was last photographed in September 2020 while holding a baby monkey.

Observation teams say they have seen groups of the two species close together in the area, and they have also photographed interbreeding.

This case may be related to habitat loss, which forced the species to live in clusters in the Kinabatangan riverside forests, the team of researchers say.

“Habitat loss or fragmentation has always been a threat to wildlife populations,” said Nadine Ruppert, primatologist and senior lecturer at Universiti Sains Malaysia. Ms. Ruppert is a co-author of the study on the mysterious monkey, which was published in the International Journal of Primatology in April.

A previous study found that forest cover in the area has decreased significantly in recent decades. Sabah lost 39.5% of its forest area between 1973 and 2010.