An unknown monkey found in Borneo is a rare hybrid between two different species competing for space in the forest, a new study suggests.

The researchers concluded that the “mystery monkey” was most likely the offspring of a proboscis monkey (Nasalis larvatus) and a silver langur (Trachypithecus cristatus) – two related species with the same habitat.

Coronavirus The restrictions prevented researchers from investigating the forest where the monkey lived, so scientists instead reviewed the photos that began appearing on social media in 2017. The monkey was first photographed as a teenager, but recent photos from 2020 show that the animal is now a mature female and may have its own baby.

“She looks like she’s taking care of a baby,” study co-author Nadine Ruppert, a primatologist at Universiti Sains Malaysia (Science University of Malaysia), told Live Science in an email. “We’re all amazed, it’s pretty surreal.”

Although different species typically do not produce viable offspring when they mate, very closely related species can occasionally interbreed in the wild to create hybrids. For example, northern pig-tailed macaques (leonine monkey) and southern pig-tailed macaques (nemestrine macaque) interbreed in some parts of Thailand, according to International Union for Conservation of Nature (IUCN). However, the interbreeding species are generally identical and belong to the same evolutionary group, or genus – the proboscis monkey and silvery langur are not.

The hybrid monkey was spotted near the Kinabatangan River in Malaysian Borneo (the island is divided into three countries: Malaysia, Brunei and Indonesia), where a range of proboscis monkeys and silvery langurs overlap. But these two types of monkey are markedly very different.

Adult proboscis monkeys have a pinkish face with an elongated nose, while the adult silvery langur has black faces with a shorter, flatter nose. Probosicis monkeys are also larger. A male proboscis monkey can grow up to 30 inches (76 cm) long and weigh 44 to 53 pounds (20 to 24 kg). Silvery langurs only reach about 22 inches (56 cm) in length and weigh 14.5 pounds (6.6 kg) on ​​average, according to New England Primate Conservancy.

A family of proboscis monkeys on a tree in Borneo.A family of proboscis monkeys on a tree in Borneo.

A group of silvery langurs, also known as silvery lutungs, sitting on a branch in Borneo.A group of silvery langurs, also known as silvery lutungs or leaf monkeys, sitting on a branch in Borneo.

Both species live in groups consisting of a dominant male and multiple females and their offspring. Men born into these groups are forced to leave when they are old enough to start their own groups, or take over another group. However, the decline in housing is limiting the areas where scattered men can go, according to Ruppert.

“We concluded from observations made by photographers that male proboscis monkeys mate with female silver langur in the area and there are mixed groups where female proboscis monkeys are still nursing babies that silver langur, ”Ruppert said.

Male proboscis monkeys may use their larger size to expel male langur and capture langur groups. The researchers suspect that the “mystery monkey” in the photos is the offspring of a male proboscis monkey and a female langur because it has characteristics of the same species. For example, her nose is pronounced like a female proboscis monkey, but not as long, and her face is gray in color.

Most hybrids born from different species are sterile and do not produce offspring, making the so -called mystery monkey and her baby even more unique. She was possibly aalmothering-or caring for another woman’s baby-but the photos showed that she had swollen breasts associated with lactation, indicating that the offspring was hers.

Although the discovery is strange and intriguing, there is a downside. “It is unfortunate that both species are now struggling together in the remaining narrow riparian forest patch surrounded by oil palm plantations, where they compete for food and marriage opportunities, ”Ruppert said.“ Hopefully people will start talking about him, not as an attraction, but as a ‘flagship’ animal of the area who needs to protect, and with him, his two parent species and their habitat. ”

The study was published April 26 at International Journal of Primatology.

Originally published in Live Science.