Rare "Mystery Monkey" Hybrid Of Distantly Related Species Found In Borneo


Rachael Funnell


Rachael Funnell

Digital Content Producer

Rachael is a writer and digital content producer at IFLScience with a Zoology degree from the University of Southampton, UK, and a nose for novelty animal stories.

Digital Content Producer

monkey hybrid borneo

The hybrid has so far only been assessed using photos but exhibits traits of two distantly related species. Image credit: Lhota et al 2022, International Journal of Primatology, CC BY 4.0

Shenanigans have been taking place in Borneo, Malaysia, as it was discovered that a proboscis monkey and a silvery langur have created a new hybrid. The “mystery monkey” is the product of two distantly related species that now share a habitat, and may possibly be competing for resources as a result of humans interfering with the landscape

Hybridization among wild animals isn’t all that rare, but the union of animals this distantly related is seldom seen, say authors of a new paper published in the International Journal of Primatology. Evidence for the species’ union includes photographs of cross-species mating plus an adult female hybrid who is thought to have offspring of her own.


The parent species behind the “mystery monkey” hybrid are believed to be the proboscis monkey Nasalis larvatus, and Trachypithecus cristatus, a species of silvery langur. Both are found in the Lower Kinabatangan Wildlife Sanctuary in Sabah, Borneo, and are thought to compete for forest space.

COVID-19 meant that researchers had to take an alternative approach to investigate the monkeys, as restrictions meant they had to keep a safe distance. Instead, they used an image library of photographs taken within the sanctuary to look for clues as to the monkeys’ lifestyles, appearances, and relationships.

The hybrid was first spotted in the photo album as a juvenile, but with fresher images providing more insights, they found evidence for her having reached adulthood and possibly even had a baby of her own.

The “putative hybrid,” as she’s affectionately referred to by the study authors, exhibits intermediate characteristics between N. larvatus and T. cristatus both in her coloration and limb proportions. Both species are known to hang out in mixed groups in the area and have even been caught on camera mating, demonstrating the arena was set for a monkey mash-up.

monkey hybrid
Photo of the hybrid and what's believed to be her baby, taken by Nicole Lee, September 7, 2020. Image credit: Lhota et al 2022, International Journal of Primatology, CC BY 4.0

While photographic evidence of the hybrid holding an infant while apparently lactating would indicate she’s fertile, the authors voice concern that her existence may be the result of human development and could threaten the species' future. The conversion of forests along the Kinabatangan River has fragmented these animals’ habitat, meaning they could now represent competitive species sharing limited resources.

The worry is that this could lead to the comparatively larger males of N. larvatus booting smaller male T. cristatus out of their groups which could, in time, lead to their local extinction.

The researchers hope to confirm the female hybrid’s identity with the aid of fecal sampling in future research once the restrictions surrounding COVID-19 are lifted. The non-invasive approach could enable them to pin down her genetic makeup once and for all.

[H/T: Live Science]


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