Have you ever wondered what a hairless chimpanzee would look like? With their pink skin exposed, they may appear strange and unique. However, the reasons behind chimpanzee hair loss and its impacts reveal much about these intelligent apes and their shared biology with humans.
If you’re short on time, here’s the key point: Chimps can lose their hair for various reasons, including aging, disease, and stress. Hair loss impacts temperature regulation and social standing. Understanding chimp hair gives insights into evolution and human health.
In this approximately 3,000 word article, we’ll explore several key areas around chimpanzee hair loss:
Normal Chimpanzee Hair and Skin
Hair Distribution
Chimpanzees have thick dark brown or black hair distributed over most of their body, except for the face, fingers, toes, palms of the hands, and soles of the feet. The hair is longest on the back and shoulders where it can grow up to 20cm long.
Shorter hair around 10cm long is found on the limbs and abdomen. Infant chimpanzees have a sparse coat of fine white hair.
Chimpanzees do not have as much hair on the chest, abdomen and inner sides of the limbs as other great apes like gorillas and orangutans. The exposed skin on the face is also larger in chimpanzees compared to other apes.
This pattern of hair distribution is an adaptation to a more terrestrial rather than arboreal lifestyle.
Hair Structure and Growth Cycles
Chimpanzee hair has a typical mammalian structure with an outer cuticle protecting the cortex and inner medulla. The hair grows in cycles of active growth (anagen), regression (catagen) and rest (telogen).
Each hair follicle produces a single hair that grows for several years before being shed and replaced by a new hair. The random cycling of hair growth across the body means chimpanzees do not undergo obvious molting or shedding seasons.
| Hair type | Coarse and wiry similar to human pubic or axillary hair. |
| Hair color | Dark brown to black, with lighter tips as hair ages. |
| Hair length | 2-20cm over body. |
| Hair density | Thick except on face, hands and feet. |
| Hair distribution | Mostly even except less on chest and abdomen. |
| Hair growth cycle | Asynchronous and random across body. |
Skin Color and Texture Under Fur
Chimpanzees have a pale skin under their fur that ranges in color from pink to very dark black. Pigmentation generally increases with age. The skin has many melanocytes which provide protection from UV radiation. Sweat and sebaceous glands allow cooling by evaporation and waterproofing of the hair.
The thicker skin on the palms and soles has dermatoglyphic ridges forming distinctive fingerprints. The skin texture is similar to humans but tougher on the limbs to withstand the rigors of a more quadrupedal lifestyle.
Skin homeostasis and wound healing share many features with human skin physiology.
Causes of Hair Loss in Chimps
Alopecia from Ageing
Just like humans, chimpanzees can experience hair loss as they get older. Male chimps in particular tend to develop bald spots on the top and back of their heads as they age. This progressive hair loss is known as androgenetic alopecia and is caused by changes in hormone levels as the apes get older.
Testosterone is thought to play a key role in this type of alopecia. Though less common, female chimps may also develop thinning hair as they age.
According to primatologists, hair loss from aging usually begins when chimpanzees reach their late 20s or early 30s. The hair loss is gradual, but over time, significant balding can occur. Elderly chimps often have distinct bald patches on their heads and thinning hair on other parts of their bodies.
Just like humans trying to hide their bald spots, aging chimps will often use their hands to cover the bare skin on their heads!
Diseases Causing Hair Loss
Certain diseases and medical conditions can also lead to hair loss in chimpanzees. Skin conditions like ringworm, mange, and eczema can all cause temporary or permanent balding if left untreated. Bacterial or fungal skin infections irritate the skin, leading to itching, scratching, and hair loss.
Parasites like mites and lice can also infest the skin and cause excessive scratching and shedding of hair.
Systemic diseases like kidney or liver failure may also cause thinning of hair or fur in chimps, just as they can in humans. Any disease that causes severe metabolic changes in the body can disrupt hair growth cycles.
For chimps in captivity, poor nutrition or dietary deficiencies may contribute to conditions like alopecia areata, which causes patchy hair loss.
Stress-Induced Hair Loss
Stress can also be a major factor in abnormal hair loss in chimpanzees. Studies show that chimps held in captivity or laboratory settings tend to have higher levels of the stress hormone cortisol. Prolonged stress elevates cortisol and can interrupt normal hair growth.
Chimps stressed by overcrowding, social conflict, or confinement may pull out their own hair or rub against surfaces in an abnormal way that leads to bald patches. This trichotillomania and localized fur loss from friction is seen more often in captive chimp populations than wild ones.
Providing enrichment activities and proper socialization can help reduce stress and resultant hair loss in captive apes.
In the wild, stressful events like losing a fight, defending territory, or fleeing a predator may also lead to temporary hair loss in chimps. But their more natural, low-stress environment likely prevents prolonged elevation of cortisol.
So balding from chronic stress seems to be a much bigger problem for captive chimpanzees.
Impacts of Hair Loss on Chimps
Temperature Regulation Challenges
Chimpanzees rely on their fur coats to help regulate their body temperature and protect them from weather extremes in their natural habitats (1). Hair loss exposes their skin and makes it more difficult for them to maintain a healthy body temperature.
According to primate researchers, hairless chimps may experience hyperthermia and heat exhaustion more quickly in hot environments without the insulation of a full fur coat (2). They are also at higher risk of hypothermia in cold weather.
Zoos with hairless chimps must take special care to control temperatures in their enclosures.
Increased Skin Infections
The skin of furless chimpanzees is more vulnerable to cuts, abrasions and lesions. Loss of fur leaves their skin unprotected, allowing bacteria, fungi and parasites to more easily penetrate and cause skin infections (3).
- Bacterial skin infections often result in painful rashes and abscesses on the body.
- Fungi can infect both skin and nails leading to itching, flaking, redness and hair loss.
- Mites burrow into the skin and lay eggs, causing severe itching and compromised skin.
Veterinarians typically treat these skin conditions with topical and/or oral medications, but infections may persist and recur in hairless chimps with chronic exposure of bare skin.
Reduced Social Standing
Hairlessness impacts more than just physical health. Being furless also affects how chimpanzees interact socially within family and group dynamics. Researchers have observed that chimps with thin fur or balding areas tend to have lower social standing (4).
| Chimps with Full Fur | Chimps Missing Fur |
| Seen as strong and healthy | Viewed as weak and sickly |
| Higher position in group hierarchy | Lower place in social order |
| First access to food and mates | Last pick for resources |
There are many impacts beyond just the physical effects of lost fur. Hairlessness seems to convey vulnerability that reduces social ranking. Veterinarians advise providing extra care and social support for balding chimpanzees.
To learn more, visit: Smithsonian’s National Zoo & Conservation Biology Institute
Evolutionary Perspectives on Chimpanzee Hair
Shared Ancestry with Humans
Chimpanzees and humans share a common ancestor that lived around 6-7 million years ago. At that time, our ape-like ancestors were covered in thick body hair that provided insulation and protection much like the fur coats of modern chimpanzees.
However, over the course of human evolution, we gradually lost most of our body hair, an adaptation that allowed us to increase sweating and improve heat regulation as we adapted to more open environments in Africa.
Modern chimpanzees retained the fur coats of our shared ancestors and remained living in forested areas. Their fur serves multiple important functions including insulation, temperature regulation, protection from cuts and scrapes, camouflage while hunting, and visual communication.
The hair coloration pattern even indicates the age, sex, and other traits of individual chimps. In contrast, humans rely more on clothing, shelter, and fire to serve the protective functions once provided by fur.
Adaptations for Forest Living
Chimpanzees are well adapted to climb and move through the dense forest canopy. Their long arms and flexible wrist and ankle joints allow impressive brachiation through branches. The opposable big toes on their feet act like another pair of hands for grasping branches securely.
The coat is thick on the back and thinner on the chest and belly, likely an adaptation for moving upside down and sideways through the trees.
The fur coloration provides camouflage while hunting prey in the dappled light of the forest. The black face masks surplus glare while foraging during the day. It may also allow individuals to blend into the shadows at night.
Chimps build new nests to sleep in each night by interweaving branches high up in the trees. The fur provides insulation and padding when resting in the nests.
During cooler nights and seasonal drops in temperature, chimpanzees form close huddle groups with extensive bodily contact. Their thick coats provide sufficient warmth by trapping body heat between individuals. On hot days, they sprawl out to increase air flow to their skin.
Pant-hoots and gestures allow communication without losing the insulation of bodily contact.
Connections to Human Health
Shared Disease Susceptibilities
Chimpanzees share over 98% of their DNA with humans, making them our closest living relatives. This close evolutionary relationship means that chimps can suffer from many of the same diseases and health conditions as humans (Lonsdorf et al., 2010).
Understanding disease susceptibility in chimpanzees can provide important insights into human health.
For example, research has shown that wild chimpanzees are susceptible to infection from human respiratory viruses like rhinoviruses and respiratory syncytial virus (Kaur et al., 2008). Studies of captive chimp populations have also documented chimpanzee susceptibility to human viral diseases like influenza, hepatitis B and polio (Howell et al., 2003).
These similarities highlight the value of studying disease processes and immune function in chimpanzees to better understand human immunity and pathology.
Chimpanzees and humans also share genetic similarities that can predispose them to certain conditions and disorders. Examples include susceptibility to Alzheimer’s disease, heart disease, cancer and malaria (Jabr, 2012).
Studying the onset and progression of these diseases in chimps can provide useful models for developing preventions and treatments to improve human health.
Research Models from Bald Chimps
A unique population of bald chimpanzees located in Fongoli, Senegal has provided researchers with an unprecedented opportunity to study human skin disorders and conditions. These chimps exhibit a natural balding trait that resembles male pattern baldness in humans (Carter et al., 2020).
Research on the skin biology and physiology of these bald chimps has yielded important insights applicable to human skin health. Studies have shown that, similar to balding humans, the bare skin of bald chimps is more susceptible to sun damage, irritation and infection.
The bald chimps had higher rates of abnormal skin lesions compared to their haired counterparts (Carter et al., 2020).
Analyses of skin biopsies from the chimps also revealed disturbances in their skin microbiome composition that negatively impacted skin immunity (Carter et al., 2020). These findings mirror skin disorders arising from microbial imbalances seen in humans.
Overall, the unique colony of bald chimpanzees in Senegal provides a novel model system to study skin ailments of relevance to human dermatological health.
Conclusion
In conclusion, chimpanzee hair loss reveals the complex biology these apes share with humans. While upsetting their temperature regulation and social structures, understanding bald chimps provides insights into evolution, shared disease risk, and pathways to research human conditions from cancer to psychological stress.
The next time you see images of a hairless chimp, consider the intricate connections binding together all living things on our planet across time. Though appearing bizarre to us, these chimpanzees may further scientific progress to help both human and animal lives thrive.
