The truth behind the 'mysterious monkey hybrid' in Malaysia

According to the researchers, the monkey hybrid found in a forest in Malaysia may have been the result of interspecific mating, which occurred due to habitat reduction.

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 networks, 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.

(From left) A female silver langur (Trachypithecus cristatus), a mysterious monkey hybrid holding her baby, and a male proboscis monkey (Nasalis larvatus). (Photo: Nature Picture Library/Alamy).

The hair of the strange monkey was long and dense, like that of a silver langur, but the sides of the face did 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 groups say they have seen groups of the two species close together in the area, and they have also photographed interspecific matings.

A, B, C, D, F are images of mysterious monkeys from childhood to adulthood. The silver langur in photo A could be its mother. In photo E is an adult male proboscis monkey mating with an adult female silver langur. (Photo: International Journal of Primatology).

This case may be related to habitat loss, which has 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.