Borneo has a hybrid 'mystery monkey,' and researchers are concerned

A new study suggests that a monkey spotted in Borneo is a rare hybrid between two different species.

Researchers concluded that the mystery monkey is the offspring of a proboscis monkey and a silvery langur, two distantly related species.

Scientists analyzed photos that appeared on social media in the year 2017, because the researchers couldn't investigate the forest where the monkey lives. The primate was first photographed as a juvenile, but recent photos show that it is now a mature female and may have an infant of her own.

Nadine Ruppert, a primatologist at the Universiti Sains Malaysia (Science University of Malaysia), told Live Science in an email that they were all in awe when they saw her nursing a baby.

These monkeys were getting hit by cars. Scientists had a solution.

While different species don't produce viable offspring if they mate, they may occasionally interbreed in the wild to create hybrid species. The International Union for the Preservation of Nature (IUCN) says that pig-tailed macaques interbreed in parts of Thailand. The proboscis monkeys and silvery langurs are not in the same evolutionary group as interbreeding species.

The Kinabatangan River in Malaysian Borneo is where the ranges of proboscis monkeys and silvery langurs overlap. The two monkey species are very different.

Adult proboscis monkeys have long noses, while adult silvery langurs have shorter noses. The monkeys are larger. A male proboscis monkey can grow up to 30 inches long and weigh up to 53 pounds. According to the New England Primate Conservancy, silvery langurs are only about 56 cm long and weigh about 14 pounds.

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The dominant male and multiple females live in groups with their offspring. Once a male matures into a group, he is pressured to leave and start his own group or take over another group. Habitat decline is limiting the areas where these males can go.

We concluded from the observations that male proboscis monkeys are having sex with female silver langurs in the area and that there are mixed groups where female proboscis monkeys take care of silver langur babies.

Male proboscis monkeys may be using their larger size to oust langur males and take over langur groups. The researchers think that the mystery monkey in the photos is the offspring of a male and female proboscis monkey. Her face has a gray tint, but her nose is pronounced like a female proboscis monkey.

The so-called mystery monkey and her baby are unusual because most hybrid babies are sterile and unable to produce offspring. She may have been taking care of another woman's baby or she may have swollen her breasts to make her offspring her own.

There is a downside to the discovery, which is that both species are competing for food and mates in the remaining narrow riparian forest patches.

The study was published in a journal.

It was originally published on Live Science.