#proboscis-monkey-nasalis-larvatus — Public Fediverse posts
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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 TwitterGentle 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 TwitterWritten 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.
Proboscis monkey side view with a large nose Slavianin/ShutterstockIn 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.
The nose is considerably smaller in female proboscis monkeys. Milan Zygmunt/ShutterstockWhat’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.
Crab-eating macaques have tiny noses by comparison. Erik Klietsch/ShutterstockWe 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.
3D model screenshots of a male proboscis monkey (left) and a female proboscis monkey (right). Male nasal aperture size is 29% larger than that of females, and males and females differ in their nasal aperture shape. Katharine Balolia/Morphosource Media (USNM521841; ID 000345556 and USNM142224; ID 000345144)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.
Making honks and nasal roars really does seem to be the evolutionary purpose of these fleshy noses. Nokuro/ShutterstockOur 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.
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Monkey minds: what we can learn from primate personality
Carla Litchfield, University of South Australia
Every human is different. Some are outgoing, while others are reserved and shy. Some are focused and diligent, while others are haphazard and unfussed. Some people are curious, others avoid novelty and enjoy their rut.
This is reflected in our personality, which is typically measured across five factors, known as the “Big Five”. These are:
Fascinating #research by @UniversitySA #primates, just like us have unique personalities. Some are chilled, while others are chaotic, some are curious while others are conservative. Some are the life of the jungle party, others shy!
- Openness – intellectual curiosity and preference for novelty
- Conscientiousness – the degree of organisation and self-discipline
- Extraversion – sociability, emotional expression and tendency to seek others’ company
- Agreeableness – degree of trust or suspicious of others and tendencies towards helpfulness and altruism, and
- Neuroticism – emotional stability or volatility.
But did you know that our primate cousins – other apes (chimpanzees, bonobos, orangutans, gorillas and gibbons) and monkeys – also exhibit a similar personality profile? Some are bold, others shy. Some are friendly, other aggressive. Some are curious, while others are conservative.
But they also differ from us in some interesting ways. And it’s in teasing out these differences that we can learn a surprising amount about the way they live, and how they have evolved.
Purple-faced Langur Semnopithecus vetulusSocial influence
Comparative psychologists have long adapted personality tests to measure the personality of other species, including pets, big cats, and our “hairy” primate relatives.
Since nonhuman animals cannot fill out a questionnaire, a human who knows them well – perhaps a caregiver, zookeeper, owner, researcher or park ranger – rates their personality for them.
Chimpanzees, it turns out, are remarkably similar to us in their personality make-up. They have been found to have the same five personality factors that we have. However, they also have a sixth Dominance factor. This includes features such as: independent, confident, fearless, intelligent, bullying and persistent.
Why do chimps have a Dominance factor and we don’t? It appears to be due to the kind of society that chimps live in. Understanding the dominance hierarchy of male chimpanzees – who is powerful and who is not – is a matter of survival and well-being for every chimpanzee in a community.
Other primates also show interesting variations in personality that correspond to their social dynamics.
Do I look conscientious or neurotic? Rod Waddington/Flickr, CC BY-SAMacaque machinations
The 22 species of macaque monkeys are the only primates that are as widespread in their distribution as we are. Along with their disparate habitats, they also have a wide variation in the structure of the societies, which appears to have influenced the evolution of their personalities.
A team of researchers, led by Mark Adams and Alexander Weiss of Edinburgh University, investigated personality and social structure in six species of macaque and found some interesting variation.
There are four main categories of social style, ranging from Grade 1 “despotic” to Grade 4 “tolerant”, depending on how strict or relaxed their female dominance hierarchies are.
Grade 1 species showed strong nepotism or favouritism towards kin and high ranking monkeys. These species include rhesus macaques, a species commonly used in laboratories and sent into space before humans, and Japanese macaques, which include the famous snow monkeys who soak in hot springs.
Lion tailed macaqueAt the other end of the spectrum, the Grade 4 species showed more tolerance in social interactions between unrelated females. This includes Tonkean macaques, which are found in Sulawesi and the nearby Togian Islands in Indonesia, and Crested macaques, which are critically endangered.
(A wild crested macaque received international attention when he stole a wildlife photographer’s camera and then photographed himself. This could be an example of a “bold” and “curious” personality.)
Red-cheeked Gibbon Nomascus gabriellaeIn the middle of the social tolerance scale are the Grade 2 and 3 species. This includes Assamese macaques, which are sometimes found at high altitudes in Nepal and Tibet, and Barbary macaques, which include the infamous “apes” of Gibraltar (actually monkeys, not apes), who are often overweight and aggressive because tourists overfeed them.
Do I look aggressive to you? Michelle Bender/Flickr, CC BY-NC-NDPersonality differences between macaque species
Interestingly, the individual species of macaques didn’t all have the same personality factors. The Japanese, Barbary, crested and Tonkean macaques had only four, while the Assamese had five, and rhesus monkeys had six factors.
All of the species exhibited the dimension of Friendliness. This seems to be a personality factor unique to macaques, and is a blend of chimpanzee Agreeableness and human Altruism.
Tonkean macaques also had a Sociability personality factor. Just like chimpanzees and humans, this species of macaque uses affiliative contacts (i.e. friendship) to reinforce bonds. Only crested macaques did not show the personality factor of Openness (i.e. curiosity), usually found in humans and other primates. The factors Dominance and Anxiety were found for rhesus and Japanese macaques.
The old and the new
The study also showed the fascinating connections between personality and social style. Grade 1 despotic species – Japanese and rhesus macaques – were rather similar, and so were Grades 2, 3 and 4, including the more tolerant species such as Assamese, Tonkean and crested macaques.
On the evolutionary scale, African primates, such as the African Barbary macaque, are “older”. Therefore, they represented the “ancestral” social behaviours for macaques.
Barbary macaque personality has a Dominance/Confidence factor, which is related to social assertiveness, an Opportunism factor, which relates to aggression and impulsivity, a Friendliness factor, relating to social affiliation, and an Openness factor, relating to curiosity and exploratory behaviour.
Rhesus and Japanese macaques, on the other hand, are “younger” on the evolutionary scale. Therefore, the Dominance and Anxiety factors seen in these species must have evolved later.
Psst. You’re disagreeable. jinterwas/Flickr, CC BYUnderstanding the personality of an individual animal or species can help in animal management and welfare. Rhesus macaques, for example, display an Anxiety personality factor. These monkeys are also most commonly used in bio-medical laboratory research. Knowing that some individuals may be prone to anxiety means that researchers must make extra efforts to alleviate any potential distress.
The findings that some Barbary macaques may be especially socially assertive, aggressive, impulsive, curious and exploratory may also help us convince tourists to keep their distance from these monkeys in Gibraltar to avoid conflicts!
Such studies of animal personality also shed light on our own personality dimensions. Our lack of a Dominance factor suggests that our ancestral environment was perhaps more egalitarian and less characterised by high social stratification, which is also borne out by anthropological and palaeontological studies.
Ultimately, we can learn a lot from our primate cousins, not only about their personalities, but about personality itself – not to mention learning a thing or two about ourselves and the social environment in which we evolved.
Carla Litchfield, Lecturer, School of Psychology, Social Work and Social Policy, University of South Australia
This article is republished from The Conversation under a Creative Commons license. Read the original article.
#amazingAnimals #animalBehaviour #animalExtinction #animalIntelligence #animalRights #animalrights #animals #CaquetáTitíMonkeyPlecturocebusCaquetensis #Primate #primates #primatology #ProboscisMonkeyNasalisLarvatus #research #RolowayMonkeyCercopithecusRoloway