Demystifying the Strange Beauty of the Proboscis Monkey’s Large Nose
Of all the #monkey species around the world, one stands out with its large, bizarre nose. In male proboscis monkeys, their bulbous noses will often hang past their mouths.But why did they evolve such a strange feature? Are they a visual sign of health and status to potential female mates, and to other males? Or did they evolve to help the monkeys make honks and other loud sounds? New groundbreaking #research has much to reveal about the mysterious large nose of the Proboscis Monkey!
Fascinating and oddly beautiful Proboscis #Monkeys of #Malaysia #Indonesia, have webbed feet and live in harems. Now #researchers discovered why they have such long noses! Help them survive when you #BoycottPalmOil #Boycott4Wildlife @palmoildetect https://wp.me/pcFhgU-5G6
Share to BlueSky
Share to Twitter
Gentle Proboscis #Monkeys of #Borneo are famous for their long noses. Until recently the reasons why baffled scientists, not anymore! They’re threatened by #palmoil #deforestation. You can help when you Boycottpalmoil #Boycott4Wildlife @palmoildetect https://wp.me/pcFhgU-5G6
Share to BlueSky
Share to Twitter
Written by Katharine Balolia, Senior Lecturer in Biological Anthropology, Australian National University The author would like to acknowledge the paper’s co-author, former ANU Masters student Pippa Fitzgerald. This article is republished from The Conversation under a Creative Commons license. Read the original article.
In our new study, published in Scientific Reports, we have deepened our understanding of these enlarged nasal structures by investigating what lies beneath: the structures in the skull.
Our findings help to explain how these noses function as visual and acoustic signals of health and status. They also add to a growing body of evidence that shows researchers can use close examinations of skulls to glean information about primate social behaviour.
A battle of noses
One of the largest monkey species in Asia, proboscis monkeys (Nasalis larvatus) are endemic to the island of Borneo. They live in coastal mangroves, peat swamps and riverine forests, and have an unusual diet made up mostly of leaves.
They can swim quite well and have webbed fingers and toes. They typically live in harem groups, made up of a single adult male (who tends to have a large, bulbous nose), some adult females and their offspring.
Males don’t often get the opportunity to attract a harem until they reach middle age. These older, dominant and large-nosed males don’t easily tolerate other large-nosed males, often trying to ward them off aggressively with deep honks and “nasal roars” – loud calls they make using their noses.
Young adult males with smaller noses often live in all-male bachelor groups, and don’t tend to fight aggressively with each other. When these bachelor males get older and become large (and large-nosed) enough to compete with males that are part of a breeding group, they are in a position to overthrow the tenured male. Females then often choose to form a harem group with this new, high-status male.
What’s behind the nose?
We investigated the size and shape of the proboscis monkey nasal cavity. That’s the bony chamber of the skull that sits behind the fleshy nose. Our goal was to find out if the size and shape of the nasal aperture – the front part of the cavity, where the fleshy nose tissue attaches – can tell us more about why these peculiar appendages evolved.
Previous research that looked at the bulbous nose in males suggests it evolved to advertise status. In our new research, we wanted to better understand how this could be the case, this time using data taken from the skull.
We used 3D surface models, downloaded from a public repository, to take size and shape measurements from 33 adult proboscis monkey skulls. We compared these with the adult skulls of king colobus monkeys, blue monkeys and crab-eating macaques, three old world monkey species.
We chose some measurements to quantify the nasal cavity, and others to quantify the nasal aperture in all the species. We also looked at tooth wear, since older adult monkeys have more worn teeth than younger adults. That would allow us to find out if older adult males had a larger nasal aperture than younger adult males.
Better honks
If male proboscis monkeys have a different nasal cavity shape to females, and a unique shape compared to the other monkey species, it would support the idea these enhanced nasal structures – both the fleshy nose and the cavity behind it – evolved to allow for more effective honks and nasal roars.
That was indeed what we found. The shape of the male nasal cavity was low and long compared to females. This allows males to build up resonance (sound vibration) in their nasal cavities, allowing them to emit deeper and louder calls through their noses.
The nasal aperture shape was also different between the sexes. In males, it looks a bit like an eggplant, while in females it looks more like an upside-down pear. This unique opening shape in males allows for higher intensity sounds to be emitted through the nose.
The sex differences in cavity shape were also larger than what we found in other old world monkey species. This further supports the idea that the nasal cavity of male proboscis monkeys underwent an evolutionary change for the purpose of making certain sounds.
Lastly, the age. Older proboscis monkey males really do have larger nasal apertures than younger adult males, but the cavity itself didn’t increase with age. This supports the idea that the large noses act as a visual signal. It’s also consistent with the fleshy nose size increasing in middle-aged or older adult males, which we know from behavioural studies in the wild.
Our evidence from the skull allows us to better understand how nasal structures in male proboscis monkeys evolved for both acoustic and visual signalling.
The more we know about how regions of the skull function as social signals, the better chance we have of reconstructing extinct primate social behaviour using fossilised skull remains.
Written by Katharine Balolia, Senior Lecturer in Biological Anthropology, Australian National University The author would like to acknowledge the paper’s co-author, former ANU Masters student Pippa Fitzgerald. This article is republished from The Conversation under a Creative Commons license. Read the original article.
ENDS
Learn about other animals endangered by palm oil and other agriculture
Global
South America
S.E. Asia
India
Africa
West Papua & PNG
Sunda Clouded Leopard Neofelis diardi
Glaucous Macaw Anodorhynchus glaucus
Attenborough’s Long-Beaked Echidna Zaglossus attenboroughi
Nancy Ma’s Night Monkey Aotus nancymaae
Maned Wolf Chrysocyon brachyurus
Tufted Ground Squirrel Rheithrosciurus macrotis
Learn about “sustainable” palm oil greenwashing
Read more about RSPO greenwashing
Lying
Fake labels
Indigenous Land-grabbing
Human rights abuses
Deforestation
Human health hazards
A 2019 World Health Organisation (WHO) report into the palm oil industry and RSPO finds extensive greenwashing of palm oil deforestation and the murder of endangered animals (i.e. biodiversity loss)
Take Action in Five Ways
1. Join the #Boycott4Wildlife on social media and subscribe to stay in the loop: Share posts from this website to your own network on Twitter, Mastadon, Instagram, Facebook and Youtube using the hashtags #Boycottpalmoil #Boycott4Wildlife.
2. Contribute stories: Academics, conservationists, scientists, indigenous rights advocates and animal rights advocates working to expose the corruption of the palm oil industry or to save animals can contribute stories to the website.
Wildlife Artist Juanchi Pérez
Mel Lumby: Dedicated Devotee to Borneo’s Living Beings
Anthropologist and Author Dr Sophie Chao
Health Physician Dr Evan Allen
The World’s Most Loved Cup: A Social, Ethical & Environmental History of Coffee by Aviary Doert
How do we stop the world’s ecosystems from going into a death spiral? A #SteadyState Economy
3. Supermarket sleuthing: Next time you’re in the supermarket, take photos of products containing palm oil. Share these to social media along with the hashtags to call out the greenwashing and ecocide of the brands who use palm oil. You can also take photos of palm oil free products and congratulate brands when they go palm oil free.
https://twitter.com/CuriousApe4/status/1526136783557529600?s=20
https://twitter.com/PhillDixon1/status/1749010345555788144?s=20
https://twitter.com/mugabe139/status/1678027567977078784?s=20
4. Take to the streets: Get in touch with Palm Oil Detectives to find out more.
5. Donate: Make a one-off or monthly donation to Palm Oil Detectives as a way of saying thank you and to help pay for ongoing running costs of the website and social media campaigns. Donate here
#animalBehaviour #AnimalBiodiversityNews #animalCommunication #animalIntelligence #animalRights #Borneo #Boycott4wildlife #BoycottPalmOil #deforestation #Indonesia #Malaysia #monkey #monkeys #PalmOil #palmOilDeforestation #palmoil #ProboscisMonkeyNasalisLarvatus #research #Researchers #SouthEastAsia
King Colobus, Colobus polykomos | New England Primate Conservancy
The king colobus (Colobus polykomos) is native to the tropical lowland and montane rainforests on the western coast of Africa, from Gambia to Côte d’Ivoire.New England Primate Conservancy
Sunda Clouded Leopard Neofelis diardi
Sunda Clouded Leopard Neofelis diardi
IUCN Status: VulnerableLocation: Brunei Darussalam; Indonesia (Sumatera, Kalimantan); Malaysia (Sarawak, Sabah)
Gliding through the rainforest canopy like a phantom predator, the Sunda Clouded Leopard moves with unmatched grace, making them one of the least understood big cats in the world. Their spectacularly patterned coat, the longest canines relative to skull size of any feline, and astonishing agility in trees set these big cats apart as a truly unique species. Yet, despite these remarkable adaptations, these mysterious carnivores are now rapidly vanishing from the wild due to human-related threats.Massive infrastructure projects, industrial-scale palm oil plantations, and poaching for the illegal wildlife trade have decimated their populations. Once thought to be a subspecies of the mainland clouded leopard, genetic studies in 2006 confirmed that they are a distinct species, found only in Borneo and Sumatra. Today, they are among the most threatened felines in the world, teetering on the edge of an uncertain future. Take action for them every time you shop and #BoycottPalmOil #Boycott4Wildlife
Sunda Clouded #leopards are agile ambush #predators 🐆 of #gibbons, wild #pigs and mouse deer in #Borneo and #Sumatra. #Palmoil deforestation is a huge threat to these #BigCats. Help them when you #Boycottpalmoil 🌴🔥💀🚫#Boycott4Wildlife @palmoildetect https://wp.me/pcFhgU-anN
Share to BlueSky
Share to TwitterSleek and elegant wild #Cats 🐱🐆 of #Indonesia 🇮🇩 and #Malaysia 🇲🇾 Sunda Clouded #Leopards are #vulnerable due to #PalmOil #Deforestation and #poaching Help them when you 🌴🩸🔥⛔️ #Boycottpalmoil #Boycott4Wildlife @palmoildetect https://wp.me/pcFhgU-anN
Share to BlueSky
Share to TwitterAppearance & Behaviour
Sunda Clouded Leopards are expert climbers, possessing a long, thick tail (equal to their body length) for balance, rotating ankle joints that allow them to descend trees headfirst, and razor-sharp retractable claws for gripping bark. Their bodies are smaller and more compact than mainland clouded leopards, making them highly agile ambush predators.They are solitary and nocturnal, moving silently through the forest to hunt primates, deer, and birds. Unlike most big cats, they purr rather than roar and rely on their extraordinarily developed senses to detect prey. Though they spend time on the forest floor, they are one of the most arboreal of all felines, capable of jumping several metres between branches.
Threats
1. Deforestation for infrastructure, timber and palm oil
- More than 50% of Borneo’s forests and two-thirds of Sumatra’s forests have been destroyed, mainly for palm oil plantations and logging.
- Mega infrastructure projects, including the Pan Borneo Highway, Trans-Sumatra Highway, and Indonesia’s new capital (Nusantara), are further severing vital forest corridors.
- Illegal logging and forest conversion continue to reduce already fragmented populations, leaving them trapped in isolated forest patches.
2. Poaching and the Illegal Wildlife Trade
Highly valued for their skins, bones, and meat, they are frequently trapped in snares. Between 2011 and 2019, at least 30 individuals were seized in the illegal trade, with live animals smuggled internationally. The rise in commercial wildlife markets has put additional pressure on an already declining population.3. Loss of Prey and Ecosystem Disruptions
Overhunting of deer, wild boar, and primates is drastically reducing their food supply. A 2024 study revealed that mesopredator release—where smaller carnivores like Sunda Leopard Cats increase in number—may be negatively impacting the number of clouded leopards.4. Human-Wildlife Conflict and Retaliatory Killings
Farmers kill clouded leopards when they prey on livestock. With deforestation pushing them into human settlements, conflict is increasing.5. Climate Change and Forest Fires
Longer dry seasons and extreme weather due to climate change are making rainforest habitats unstable and food sources scarcer. Fires, caused by land clearing for palm oil plantations, are destroying crucial remaining habitat.Geographic Range
The Sunda Clouded Leopard (Neofelis diardi) is found only on the Southeast Asian islands of Borneo and Sumatra. Known locally as rimau-dahan (“tree tiger” in Malay) and entulu in Sarawak, these elusive big cats thrive in dense rainforests, where their exceptional climbing skills and camouflage allow them to hunt undetected. They are particularly dependent on lowland primary forests but have been increasingly pushed into montane and secondary forests due to rampant deforestation.Key Habitats:
- Sumatra – Leuser Ecosystem, Kerinci Seblat National Park, Bukit Barisan Selatan National Park
- Borneo – Kalimantan (Indonesian Borneo), Sabah and Sarawak (Malaysian Borneo), Brunei Darussalam
- Heart of Borneo Landscape – This transboundary rainforest, spanning Brunei, Malaysian Borneo, and Indonesian Kalimantan, serves as one of the last strongholds for the species.
Diet
Sunda Clouded Leopards are apex rainforest predators, feeding on:
- Primates – Gibbons, macaques, langurs
- Ungulates – Mouse deer, muntjac, young bearded pigs
- Birds, rodents, and reptiles
- Occasionally livestock in fragmented forest areas
Their hunting strategy involves stealth and ambush, using their powerful jaws and canines to deliver a fatal bite to the neck. As their habitat shrinks, they are increasingly forced into human settlements, where they are often shot in retaliation.
Mating and Reproduction
Little is known about their breeding behaviour, however:
- They reach sexual maturity at around two years old.
- Gestation lasts 85–95 days, producing 1–5 cubs (typically 2).
- Cubs remain hidden in dense vegetation for the first five months.
- Mothers raise cubs alone, teaching them to hunt before they become independent.
- Their slow reproductive rate, combined with habitat destruction, makes population recovery extremely difficult.
FAQs
Are Sunda Clouded Leopards dangerous to humans?
No. Sunda Clouded Leopards are extremely elusive and prefer to avoid human contact. They only venture into human areas when forced by habitat loss.How are they different from mainland Clouded Leopards?
Sunda Clouded Leopards (Neofelis diardi) were originally thought to be the same species as the Indochinese Clouded Leopard (Neofelis nebulosa), but genetic studies in 2006 confirmed that they are separate species.• Genetic divergence: The two species diverged between 2 million and 900,000 years ago, likely when rising sea levels isolated Borneo and Sumatra from the mainland.
• Physical differences: Sunda Clouded Leopards have darker fur, smaller cloud markings, and a more robust build, whereas Indochinese Clouded Leopards are lighter in colour with larger, more defined markings.
• Habitat preferences: Sunda Clouded Leopards rarely descend to the forest floor, whereas Indochinese Clouded Leopards hunt both in trees and on the ground.
Why are they called “Tree Tigers”?
The Malay name rimau-dahan means “tree tiger”, as they are among the best tree-climbing predators in the world. This name comes from their incredible climbing skills and their resemblance to big cats like tigers. Their large paws, long tail, and flexible ankles make them exceptional tree climbers, often leaping between branches or ambushing prey from above.Are Sunda Clouded Leopards extinct anywhere?
They were once found on Java, but are now extinct there.How many Sunda Clouded Leopards are left?
Estimates suggest there are fewer than 10,000 mature individuals, but deforestation and poaching are causing rapid declines. Exact numbers are hard to determine due to their elusive nature.Take Action!
Every time you shop, choose 100% palm oil-free products to avoid contributing to deforestation. #BoycottPalmOil #Boycott4Wildlife
- Boycott palm oil and products that contribute to rainforest destruction.
- Support conservation efforts protecting Borneo and Sumatra’s last remaining forests.
- Advocate for stronger anti-poaching laws and enforcement.
Support Sunda Clouded Leopards by going vegan and boycotting palm oil in the supermarket, it’s the #Boycott4Wildlife
Support the conservation of this species
This animal has no protections in place. Read about other forgotten species here. Create art to support this forgotten animal or raise awareness about them by sharing this post and using the #Boycottpalmoil #Boycott4Wildlife hashtags on social media. Also you can boycott palm oil in the supermarket.Further Information
Cowan, C. (2024, April 29). Borneo and Sumatra megaprojects are carving up clouded leopard forests. Mongabay. https://news.mongabay.com/2024/04/borneo-and-sumatra-megaprojects-are-carving-up-clouded-leopard-forests/Buckley-Beason, V. A., Johnson, W. E., Nash, W. G., Stanyon, R., Menninger, J. C., Driscoll, C. A., Howard, J., Bush, M., Page, J. E., Roelke, M. E., Stone, G., Martelli, P., Wen, C., Ling, L., Duraisingam, R. K., Lam, P. V., & O’Brien, S. J. (2006). Molecular evidence for species-level distinctions in clouded leopards. Current Biology, 16(23), 2371–2376. https://doi.org/10.1016/j.cub.2006.08.066
Haidir, I., Macdonald, D. W., & Linkie, M. (2020). Sunda clouded leopard (Neofelis diardi) densities and human activities in the humid evergreen rainforests of Sumatra. Oryx, 55(2), 189-196. https://doi.org/10.1017/S0030605319001005
Hearn, A., Ross, J., Brodie, J., Cheyne, S., Haidir, I.A., Loken, B., Mathai, J., Wilting, A. & McCarthy, J. 2015. Neofelis diardi (errata version published in 2016). The IUCN Red List of Threatened Species 2015: e.T136603A97212874. https://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T136603A50664601.en. Accessed on 26 February 2025.
Kaszta, Z., Cushman, S. A., Hearn, A. J., Burnham, D., Macdonald, E. A., Goossens, B., Nathan, S., & Macdonald, D. W. (2019). Integrating Sunda clouded leopard (Neofelis diardi) conservation into development and restoration planning in Sabah, Borneo. Biological Conservation, 235(4). https://doi.org/10.1016/j.biocon.2019.04.001
Mayhew, D. S., Hearn, A. J., Devineau, O., Linnell, J. D. C., & Macdonald, D. W. (2024). Loss of Sunda clouded leopards and forest integrity drive potential impacts of mesopredator release on vulnerable avifauna. Heliyon, 10(12), e32801. https://doi.org/10.1016/j.heliyon.2024.e32801
Wikipedia. (n.d.). Sunda Clouded Leopard. https://en.m.wikipedia.org/wiki/Sunda_clouded_leopard
Wong, W.-M. (2021, September 17). Species Spotlight: Sunda Clouded Leopard, the Ethereal and Declining ‘Tree Tiger’. The Revelator. https://therevelator.org/species-spotlight-sunda-clouded-leopard/
How can I help the #Boycott4Wildlife?
Take Action in Five Ways
1. Join the #Boycott4Wildlife on social media and subscribe to stay in the loop: Share posts from this website to your own network on Twitter, Mastadon, Instagram, Facebook and Youtube using the hashtags #Boycottpalmoil #Boycott4Wildlife.2. Contribute stories: Academics, conservationists, scientists, indigenous rights advocates and animal rights advocates working to expose the corruption of the palm oil industry or to save animals can contribute stories to the website.
Wildlife Artist Juanchi Pérez
Mel Lumby: Dedicated Devotee to Borneo’s Living Beings
Anthropologist and Author Dr Sophie Chao
Health Physician Dr Evan Allen
The World’s Most Loved Cup: A Social, Ethical & Environmental History of Coffee by Aviary Doert
How do we stop the world’s ecosystems from going into a death spiral? A #SteadyState Economy
3. Supermarket sleuthing: Next time you’re in the supermarket, take photos of products containing palm oil. Share these to social media along with the hashtags to call out the greenwashing and ecocide of the brands who use palm oil. You can also take photos of palm oil free products and congratulate brands when they go palm oil free.
https://twitter.com/CuriousApe4/status/1526136783557529600?s=20
https://twitter.com/PhillDixon1/status/1749010345555788144?s=20
https://twitter.com/mugabe139/status/1678027567977078784?s=20
4. Take to the streets: Get in touch with Palm Oil Detectives to find out more.
5. Donate: Make a one-off or monthly donation to Palm Oil Detectives as a way of saying thank you and to help pay for ongoing running costs of the website and social media campaigns. Donate here
Learn about other animals endangered by palm oil and other agriculture
Global
South America
S.E. Asia
India
Africa
West Papua & PNG
Glaucous Macaw Anodorhynchus glaucus
Attenborough’s Long-Beaked Echidna Zaglossus attenboroughi
Nancy Ma’s Night Monkey Aotus nancymaae
Maned Wolf Chrysocyon brachyurus
Tufted Ground Squirrel Rheithrosciurus macrotis
Visayan Broadbill Sarcophanops samarensis
Learn about “sustainable” palm oil greenwashing
Read more about RSPO greenwashing
Lying
Fake labels
Indigenous Land-grabbing
Human rights abuses
Deforestation
Human health hazardsA 2019 World Health Organisation (WHO) report into the palm oil industry and RSPO finds extensive greenwashing of palm oil deforestation and the murder of endangered animals (i.e. biodiversity loss)
#animals #bigCat #bigcat #bigcats #Borneo #Boycott4wildlife #BoycottPalmOil #Brunei #carnivores #cats #deforestation #ForgottenAnimals #Gibbons #hunting #Indonesia #Kalimantan #leopard #leopards #Malaysia #PalmOil #palmOilDeforestation #palmoil #Pigs #poaching #predators #Sarawak #SEAsia #SouthEastAsia #Sumatra #SundaCloudedLeopardNeofelisDiardi #vulnerable
Species Spotlight: Sunda Clouded Leopard, the Ethereal and Declining ‘Tree Tiger’ • The Revelator
Isolated on just two islands in Asia, this forest-dependent wild cat persists in the region experiencing the world’s fastest deforestation.Wai-Ming Wong (The Revelator)
Lo, thar be cookies on this site to keep track of your login. By clicking 'okay', you are CONSENTING to this.