top of page

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

By: April Carson

Brenden Miles was on a tour through the Kinabatangan River in Malaysia's Borneo region when he noticed an unusual primate for the first time in his life. He took a few images of the odd monkey and, upon returning home, examined them. What he found was a new species of hybrid monkey, which he named the 'Borneo mystery monkey.'

The primate-like creature was first identified as a species with "unusual color variation" when the team discovered the image on Facebook. According to Miles, at first he thought it might be a morph of the silvered leaf monkey, which is a member of the group with uncommon color variation. But then he noted other minor specifics. “Its nose was longer than that of a proboscis monkey, and its tail thicker than that of a silvered leaf [monkey],” he explains. He forgot all about it and posted a picture of the animal on Facebook.

The “mystery monkey" in the original photo and others appears to be a hybrid of two distantly related primate species that share the same fragmented habitat, according to an analysis of that image and others.

The monkey’s mother was likely a silvered leaf monkey, a species found in both Borneo and Sumatra. The father is more difficult to identify but is thought to be either a proboscis monkey, unique to Borneo, or an entellus monkey, found in both India and Sri Lanka.

Researchers claim that a male proboscis monkey (Nasalis larvatus) met a female silvered leaf monkey (Trachypithecus cristatus) to produce the purported offspring on April 26 in the International Journal of Primatology. And they're concerned about the creature's parent species, to say the least.

Hybridization between closely related species has been documented in captivity and occasionally in the wild (SN: 7/23/21). “But hybridization across genus is extremely unusual,” says Ramesh Boonratana, the regional vice-chair for Southeast Asia for the International Union for Conservation of Nature's primate specialist group.

According to primatologist Nadine Ruppert, habitat devastation, fragmentation, and deterioration as a result of expanding palm oil plantations along the Kinabatangan River might explain how the hybrid arose.

one another — share an environment, they may interact with one another but seldom mate. Cross-genera hybridization happens only when there is a pressing environmental need, according to Ruppert of Universiti Sains Malaysia in Penang Island.

Deforestation accelerated after the discovery of oil, with government plans to exploit it as a resource in 1974. From 1973 to 2010, Sabah's percentage of forest cover fell by about 40%, owing mostly to logging and palm oil plantations.

The orangutan is one of the world's most endangered primates, and its plight is intricately linked to palm oil.

The palm oil industry has been blamed for destroying the habitat of many animals, including the Bornean orangutan (Pongo pygmaeus), which are found only on the island of Borneo.

“Both species are found in small forest patches along the river in certain areas,” Ruppert adds. This causes competition for food, mates, and other resources. “Because the animals are unable to spread away from each other, the larger species' male - the proboscis monkey — can easily supplant the silvered leaf monkey's male.

Since 2016, there have been additional confirmed sightings of the enigma monkey, albeit these were sporadic. For now, the uncommon sightings and COVID-19 pandemic have prevented scientists from obtaining feces samples for genetic analysis in order to identify the monkey's origin. Rather, Ruppert and colleagues compared images of the potential hybrid with those of the parent species both visually and based on limb ratios. “All of its measurements, if it was from one of the two parent species, would be similar to that of one species,” says Ruppert. “That is not the case with this animal, however.

The researchers' conclusion has been bolstered by a photo of a male proboscis monkey mating with a female silvered leaf monkey, as well as stories from boat operators and tour guides about a single male proboscis monkey hanging around a troop of female silvered leaf monkeys.

However, Ruppert is concerned for the well-being of both parent species in light of the mystery monkey's popularity. Proboscis monkeys are listed as endangered by the International Union for Conservation of Nature, while silvered leaf monkeys are vulnerable. “The hybrid is gorgeous, but we don't want to see any more of them,” explains Ruppert. “Both species should have a large enough habitat so they can perform their natural behaviors over time and enough food to do so."

Rising temperatures, changing land uses, and habitat loss or fragmentation may cause more instances of mating - or at least, attempts at mating - between species or even genera in Borneo and elsewhere as a consequence of climate change.

The strange monkey was last seen in September 2020, when it had swollen breasts and was cradling a child, implying that the animal is a producing female. That's another unanticipated finding, according to the researchers, because most crossbreeds are infertile.

The discovery of the Bornean mystery monkey is yet another example of how climate change can lead to new and unexpected hybrid animal species. As rising temperatures and changes to land usage continues, there's a possibility that we may see even more of these hybrids in the future.

This article was originally published on

S1E3 Poltergeists and the Paranormal

Please join us for the Black Knight Satellite The Untold Story movie premiere. A live red carpet event will take place, with Billy Carson taking questions and providing answers on the red carpet. Meet Billy Carson at the LIVE Premiere! Click below for more details.



About the Blogger:

April Carson is the daughter of Billy Carson. She received her bachelor's degree in Social Sciences from Jacksonville University, where she was also on the Women's Basketball team. She now has a successful clothing company that specializes in organic baby clothes and other items. Take a look at their most popular fall fashions on

To read more of April's blogs, check out her website! She publishes new blogs on a daily basis, including the most helpful mommy advice and baby care tips! Follow on IG @bossbabymav



Are you a member of the 4BK TV Channel? If not, you should want to become one!!

On, you can Expand your mind and explore your consciousness in our collection of workshops by Billy Carson, including Remote viewing - Ancient History - Anomaly Hunting, and how to Manifest the things in life you've always desired

Start your 3-day FREE trial now!




bottom of page