Orangutans wear a coat that spans a surprisingly wide palette, from pale cinnamon and bright ginger to deep rusty maroon, depending on species, age, sex, and the individual animal. No single shade defines the entire genus. The three recognized species each tend toward a slightly different part of that spectrum, and an individual orangutan’s color shifts over the course of its life. What makes their coloring especially interesting is that the pigment responsible is the same one behind human red hair, yet the genetic route to that reddish tone turns out to be completely different.
Three Species, Three Tendencies
Until 2017, scientists recognized two species of orangutan. Today there are three: the Bornean orangutan (Pongo pygmaeus), the Sumatran orangutan (Pongo abelii), and the Tapanuli orangutan (Pongo tapanuliensis), found only in a small highland area of northern Sumatra. Each has a somewhat different look, hair texture included.
Bornean orangutans tend toward the darker end of the range. Their coats often read as a deep auburn or chocolate-tinged maroon, and their hair lies relatively flat against the body. Sumatran orangutans are generally lighter and longer-haired, with coats closer to cinnamon or bright orange, and conspicuously shaggier faces. Tapanuli orangutans, the most recently described species, have been characterized as having frizzier, more cinnamon-toned hair and smaller, flatter facial flanges in adult males. These are generalizations: within any wild population you can find individuals that look noticeably lighter or darker than average. Coat color in orangutans varies across individuals at least as much as hair color varies across a room of red-haired people.
Why Orangutans Are Red
The color itself comes down to pigment chemistry. Mammalian hair color is produced by melanin, which comes in two main forms: eumelanin, which produces blacks and browns, and pheomelanin, which produces reds and yellows. Orangutan hair is dominated by pheomelanin, which is why the overall impression is warmly reddish rather than the dark brown or black that characterizes most other great apes.
A reasonable first guess would be that orangutans are red for the same reason some humans are: a change in the MC1R gene, the gene most famously linked to red hair in people of European descent. In red-haired humans, certain variants of MC1R result in a receptor that does not function properly, causing melanocytes to produce pheomelanin instead of eumelanin. Researchers tested whether the same thing was happening in orangutans and found it was not. The orangutan MC1R receptor works. Pharmacological testing showed it binds its signaling molecules and produces an intracellular response, with only a slightly lower response to one particular hormone and a mildly elevated baseline activity compared with the human version. In other words, the orangutan’s MC1R gene has not broken down the way it has in red-haired humans. The reddish coat evolved through a different, still-unidentified genetic pathway.
1Molecular Biology and Evolution. High Diversity in Functional Properties of Melanocortin 1 Receptor (MC1R) in Divergent Primate Species Is More Strongly Associated with Phylogeny than Coat ColorThis makes orangutan coloring an example of convergent evolution: two lineages arriving at a visually similar result through completely separate genetic mechanisms. The implication is that whatever selective pressure or genetic drift pushed orangutans toward pheomelanin-heavy hair, it did not involve the same molecular shortcut that accounts for red hair in humans.
1Molecular Biology and Evolution. High Diversity in Functional Properties of Melanocortin 1 Receptor (MC1R) in Divergent Primate Species Is More Strongly Associated with Phylogeny than Coat ColorHow Color Changes From Infancy to Adulthood
An orangutan does not look the same color throughout its life. Newborns and very young infants are typically covered in sparse, light-colored, somewhat wispy hair that sticks out from the body. As the animal grows, the coat texture and color both change markedly. In Bornean orangutans, the scattered, erect hairs that characterize infants give way to thicker, denser hair that lies closer to the head by around the age of seven. The overall pelage tends to deepen in hue as the animal matures, so that a bright ginger infant may grow into a dark auburn adult.
2PubMed. Developmental changes in the facial morphology of the Borneo orangutan (Pongo pygmaeus): possible signals in visual communicationThese changes are not just cosmetic quirks. Researchers who tracked Bornean orangutan facial development concluded that the light, fluffy infant coat and the pale skin patches around the eyes and mouth function as infant signals, visual cues that communicate the animal’s age and vulnerability to other group members. As those signals fade and are replaced by darker skin, heavier hair, whiskers, and a beard after about age seven, the animal starts broadcasting its transition toward adulthood. The shift happens in both sexes, though the timing of certain details differs between males and females.
2PubMed. Developmental changes in the facial morphology of the Borneo orangutan (Pongo pygmaeus): possible signals in visual communicationSkin and Face Color Tell Their Own Story
When people picture an orangutan, the red hair dominates the mental image. But the skin underneath, and especially the skin of the face, carries its own suite of colors and changes that are just as interesting from a biological standpoint.
Infant Bornean orangutans have conspicuously light-colored skin around their eyes and mouths. This pale ring is most prominent in animals younger than about three years, then rapidly shrinks in area through roughly age seven. The darkening of facial skin continues well past that. In females, the eyelids stay white even past the age of ten and do not turn black until around twenty. In males, the eyelids darken earlier, turning black before age ten. Adult orangutans of both sexes end up with predominantly dark facial skin, though the exact shade can range from dark grey to almost black.
2PubMed. Developmental changes in the facial morphology of the Borneo orangutan (Pongo pygmaeus): possible signals in visual communicationThe most dramatic facial feature belongs to fully mature, flanged males. These males develop large cheek pads called flanges that frame the face in a broad disc. The flanges are dark-skinned and largely bare, creating a high-contrast frame against the surrounding red hair. Flanged males also develop a large throat pouch and produce long calls that carry through the forest. Not all adult males develop flanges; some remain in an “unflanged” state for years or even permanently, retaining a more slender face that resembles a female’s. The reasons for this developmental divergence involve social competition and hormonal regulation and remain an active area of research. But in color terms, the difference is stark: a flanged male’s face is a massive dark oval bordered by long red hair, while an unflanged male’s face is smaller, lighter, and less visually imposing.
Is Orange Good Camouflage in a Rainforest?
To a human walking through a Bornean or Sumatran forest, an orangutan looks strikingly visible. That bright reddish-orange against green foliage seems about as far from camouflage as you can get. But color perception is not universal across species, and the answer changes when you consider how other animals actually see.
Research on primate coat conspicuousness found that orange coloration, while eye-catching to humans, would be cryptic amongst foliage to many primates, including to all males and many females of the orange-furred species’ own kind. This is because the ability to distinguish red and orange from green depends on having trichromatic color vision, meaning three types of cone cells in the retina. Many primates are dichromatic (two cone types), which makes reds and greens much harder to tell apart. Most potential predators of primates, and many of their primate neighbors, fall into this dichromatic category.
3American Journal of Primatology. Colors of primate pelage and skin: objective assessment of conspicuousnessOrangutans themselves are trichromats, as are all Old World primates and apes, so they can see each other’s color perfectly well. But against the dappled light of a tropical canopy, where filtered sunlight creates complex patches of gold, brown, and green, even a human trichromat can lose sight of a motionless orangutan at moderate distance. The reddish hair blends into the warm tones of bark, dead leaves, and sun-dappled branches. In practical terms, orangutans are not as conspicuous in their natural habitat as they appear in a zoo enclosure or a photograph with a clean green background.
Color Variation You Can See in Captivity
Zoo visitors sometimes notice that orangutans in one facility look quite different in color from those at another, and this is not always just species differences. Captive orangutans live under very different conditions than wild ones: controlled diets, UV-filtered light, climate-controlled enclosures, and sometimes generations of breeding that mix Bornean and Sumatran lineages (though modern breeding programs work hard to prevent this). All of these factors can subtly affect coat appearance.
Sunlight exposure plays a role. Wild orangutans spend their days in variable light, from deep canopy shade to direct tropical sun. Prolonged UV exposure can bleach pheomelanin slightly, producing lighter tips on the hair shafts, a process familiar to anyone who has noticed their own hair lighten over a summer. Captive animals that spend more time indoors or under filtered light may retain darker, more saturated color. Diet could theoretically influence coat quality as well, since nutritional deficiencies sometimes dull hair in mammals, though this has not been rigorously studied in orangutans.
Age-related graying also occurs. Elderly orangutans, particularly those in their thirties and forties, may show patches of grey or whitened hair, much the way humans do. The bright orange of a young adult slowly gives way to something more muted and streaked. In the wild, few orangutans reach the extreme old ages sometimes seen in captivity, so dramatic graying is more commonly observed in zoo populations.
Why the Underlying Genetics Remain Murky
Given that the MC1R gene does not explain orangutan redness, the obvious question is: what does? The honest answer is that researchers do not yet know. Coat color genetics in non-model organisms (species that are not lab mice or domesticated animals) is still a developing field. In mice, dozens of genes influence coat color, and the same is probably true for primates, but mapping those genes in a critically endangered, slow-breeding wild ape is far more difficult than in a mouse colony.
One candidate pathway involves the regulation of how much pheomelanin versus eumelanin melanocytes produce, which can be controlled at many points beyond just the MC1R receptor. Genes affecting the availability of cysteine (a building block of pheomelanin), the activity of enzymes downstream of MC1R signaling, or the transport of pigment granules into the growing hair shaft could all contribute. For now, all of these remain plausible but unproven. The research that ruled out MC1R as the explanation also noted that the orangutan MC1R carries thirteen amino acid differences from the human version, three of which arose specifically along the orangutan lineage after it split from the other great apes.
1Molecular Biology and Evolution. High Diversity in Functional Properties of Melanocortin 1 Receptor (MC1R) in Divergent Primate Species Is More Strongly Associated with Phylogeny than Coat ColorThe difficulty of answering this question also reflects priorities. Orangutan conservation biology tends to focus on habitat loss, fragmentation, population genetics for breeding management, and disease. Coat-color genetics, while scientifically interesting, sits lower on the priority list for the small number of research groups working on orangutan genomics.
How Orangutan Color Compares to Other Red Primates
Orangutans are not the only red primates, though they are the most famous. Red howler monkeys, red-shanked doucs, golden lion tamarins, and some lemur species all display strikingly reddish or orange fur. Interestingly, the conspicuousness research mentioned earlier found that orange coloration crops up across multiple primate lineages, including in both Old World and New World monkeys, and often appears cryptic rather than showy when evaluated against the visual systems of each species’ actual ecological community.
3American Journal of Primatology. Colors of primate pelage and skin: objective assessment of conspicuousnessWhat sets orangutans apart is the combination of their reddish fur with their sheer size and their largely solitary, arboreal lifestyle. A golden lion tamarin weighing half a kilogram and an orangutan weighing eighty kilograms are working with the same pigment family, but the visual effect and the ecological context are vastly different. For an orangutan, the long, flowing reddish hair also serves as insulation and rain-shedding in a tropical downpour. Wild orangutans sometimes drape large leaves over their heads in the rain, but the hair itself is coarse and oily enough to repel a fair amount of water, and its length and density help maintain body temperature during cool, wet nights in the canopy.
What Flanges, Beards, and Long Hair Signal to Other Orangutans
Beyond the baseline reddish coat, orangutans develop a range of secondary features whose visual impact builds on or contrasts with their hair color. Fully flanged adult males grow enormous cheek pads, a throat pouch, and a cape of especially long hair on their arms and back. This long hair, often the deepest and most saturated red-brown on the animal’s body, makes the male look physically larger and more imposing. When a flanged male displays by shaking branches or producing long calls, the flowing arm hair amplifies every movement.
Females develop beards and whiskers as they age, and these facial features darken along with the rest of the face. In Bornean orangutans, the transition from the pale-faced, wispy-haired juvenile to the dark-faced, bearded adult provides a visual timeline of maturity. Researchers have suggested that these progressive changes serve as honest signals of age and reproductive status, readable at a distance through the forest canopy. An orangutan encountering another at the edge of visibility can assess, from the silhouette and contrast of dark face against red hair, whether it is looking at an infant, a subadult, an adult female, an unflanged male, or a flanged male, each of which calls for a different social response.
2PubMed. Developmental changes in the facial morphology of the Borneo orangutan (Pongo pygmaeus): possible signals in visual communicationThe interplay between red hair and dark skin is itself part of the signal. High contrast is easier to detect at a distance and in low light, which matters for an animal that lives in a dimly lit forest interior and communicates primarily through visual and acoustic channels rather than close-range grooming and touch, as more social primates do. For an animal whose social encounters are infrequent and sometimes tense, being able to broadcast identity and status from far away has clear advantages.