- Sweating is an adaptation that helps some animals cope with heat but it is relatively rare.
- Horses have the most efficient sweating and cooling system with humans coming in second.
- While donkeys and zebras can sweat, they only sweat heavily when under high stress or pain.
Sweat might be messy, smelly, and generally unappealing, but it is an important human phenomenon that helps to make us what we are. Perspiration is a cooling mechanism that kicks in to keep the internal body temperature at a reasonable 98.6 degrees Fahrenheit. Primarily composed of water, potassium, salt, and other minerals, sweat literally serves to release excess heat generated by the muscles when other methods of cooling have failed. Otherwise, if we did not sweat, we would overheat and die. But did you know that there are animals that sweat, too?
Despite how necessary it is for human health, perspiration is a rare phenomenon in the animal kingdom. True sweating is mostly limited to primates and equines. Instead, most animals have evolved to regulate their body temperature in all kinds of different ways, including panting, rolling around in the mud, swimming in the water, lounging in shade, and urinating or defecating all over one’s body. Some animals also have exceptionally long ears with a lot of blood vessels that release excess heat into the air.
The anatomy of sweating is critical to understanding how it works. To simplify things a little, there are generally two different types of sweat glands: the apocrine glands and eccrine glands. Apocrine glands, located near the base of the hair follicles, have primarily evolved for the purpose of producing odors as pheromones, territorial markers, and warning signals; they’re very rarely used to cool the body on warm days (though there are some exceptions). Eccrine glands, located close to the surface of the skin, mostly produce sweat for the purpose of thermoregulation.
The majority of mammals are covered in apocrine glands over most of their body. Primates (chimps and gorillas in particular) are the only group of mammals with a relatively high number of eccrine glands in comparison to apocrine glands.
Humans are likewise the only species on the planet whose bodies are almost completely covered in eccrine glands (except for a few places like the armpits, ear canals, eyelids, and nipples). We contain between two million and five million of these glands all over our bodies. Together they produce around 12 liters of sweat a day.
The evolution of (relatively) bare skin was believed to be a necessary precondition for the evolution of sweat in humans. Sweat easily evaporates from bare skin, whereas it would accumulate and gather around dense hair follicles, which would have a counterproductive effect. The evolution of sweat in turn allowed humans to hunt game over long distances on hot days, while most other species would easily overheat.
With all that background detail in place, this article will consider the top 7 animals (besides humans) that produce some form of perspiration. The list will only include the animals that sweat to release heat, cool the body, or moisturize the skin in some way. It will not include general perspiration for other survival purposes.
#7 Horses and Donkeys
Anyone who has ever worked with horses for long enough will notice that they do sweat heavily when they are working hard. They also have the ability to produce a type of foam or lather over their bodies, particularly around the hind legs and neck, when exercising or working in hot environments. This foam contains a unique protein called latherin that gives the sweat a foamy appearance when it is in an area where friction occurs, such as between the thighs.
The latherin allows the perspiration to work through the entire surface of the waterproof hair, from the base to the tip. This in turn increases its exposure to air so it will eventually evaporate from the body. Latherin is also present in saliva, where it helps the horse to chew high-fiber foods.
When it’s working particularly hard, a horse can easily lose around 4 gallons of sweat per hour, depending on the intensity of the exercise and the temperature of the surrounding environment. By comparison, a horse typically drinks between 10 and 20 gallons of water per day. The effectiveness of this cooling system reduces the need for the horse to pant very much in hot conditions, and it may be a sign of a health problem if the horse cannot properly sweat.
Horses have an extensive network of blood vessels just under the skin that help them regulate their body temperature. When they sweat in hot weather, these blood vessels expand to maximize the amount of heat dissipated. In cold weather, the blood vessel contract and divert blood flow deeper in the body. This is one of the specialized mechanisms that allow the horse to be such an amazing athlete.
While donkeys are also able to sweat, they do so much less than a horse. The donkey’s primary method of dispersing extra heat is through its large ears which have multiple blood vessels close to the surface of the skin so that heat can escape. Donkeys do not have the same blood vessels that horses do under their skin so they are not able to adapt to changes in temperature as quickly as horses can. Donkeys generally only sweat when they are under severe stress so it should be seen as a sign that the donkey is in distress and may need help.
Zebras, just like horses and donkeys, are a member of the genus Equus. It’s, therefore, no surprise that their bodies also have the ability to create the same foamy latherin that helps to facilitate evaporation and cooling around the hair. What’s particularly fascinating about the zebra is that the latherin might interact with the stripes in unique ways. Some scientists have speculated that erect black hairs could promote sweat evaporation during the hottest parts of the day.
The evolution of zebra stripes still remains a contentious subject, however, and thermoregulation is just one hypothesis among many others. In general, Zebras are much more similar to donkeys than to horses.
The chimpanzee is often said to be humanity’s closest living relative because we share some 98.8% of the same DNA. One of the traits we share in common with them is the ability to sweat.
As mentioned previously, chimpanzees have a high ratio of eccrine to apocrine glands, presumably to help them regulate the temperature of their bodies. Nevertheless, their sweating isn’t quite as efficient as a person’s, both because of a lower density of glands on their skin and because of their thick fur. For this reason, the chimpanzee still relies on other methods to stay cool.
Another close human relative, gorillas also have the ability to sweat in warm weather to remain cool and comfortable, but thermoregulation is only one purpose of the sweat glands.
Just like chimpanzees and humans, gorillas have a specialized tissue called axilla or axillary organ located on the armpits. This organ is particularly pronounced in male gorillas. It is composed of four to six layers of glands that secrete sweat and other scents. This actually serves the primary purpose of facilitating communication within the entire group. The scent provides an alarm signal to other group members when potential threats are lurking nearby. It’s also a useful sign of reproductive availability.
For some unknown reason, humans still retain the strong armpit odor, despite seemingly serving little purpose. This has generated a bit of a scientific mystery.
#3 Old World Monkeys
The Old World monkey is an entire family of primates, mostly native to Africa and Asia. Macaques and baboons are the most well-known members of this group. It does not include New World monkeys, like marmosets and tamarins, as well as the lemurs of Madagascar.
The macaque is a genus of Old World monkeys; there are 23 species within this group, most of them native to Asia. The best-known species are probably the Rhesus macaque and the Japanese macaque. While they do have the ability to sweat, it’s not quite as pronounced as their great ape cousins. This is probably due to the fact that they have a fairly even split between eccrine and apocrine glands on their skin.
The baboon is another genus of Old World monkeys, comprising six distinct species native to Africa and the Arabian Peninsula. They are characterized by a dog-like muzzle, powerful jaws, sharp teeth, short tails, a relatively large body size, and protruding buttocks. Baboons also appear to have quite a few eccrine glands covering their bodies. Some studies confirm that they do, in fact, produce sweat in response to heat.
You may be a little surprised to learn that dogs have a cluster of eccrine glands (sometimes also called merocrine glands) around their paw pads. These have a similar function as human sweat glands to cool the body. If you look closely, you can sometimes see perspiration gathering around the paws during a hot day. The relatively bare skin makes perspiration possible. But this is also why the sweat is restricted to the paw pads only.
Because of their thick fur, dogs cannot sweat over most of their bodies. They must still pant to remain cool. Given that their ability to sweat is so limited and rather inefficient, dogs can over heat relatively quickly. A good way to help them cool down is to place their feet in cool water.
Despite popular misconception, the hippopotamus does not produce true sweat at all, but it’s still fascinating for a different reason. This big semi-aquatic African herbivore secretes a red sticky mucus-filled liquid that functions as a kind of moisturizer, sunscreen, and antibiotic. This perspiration is initially colorless, but it actually turns red and brown when reacting with certain pigments. People have given it the nickname of blood sweat, even though it contains neither blood nor true sweat.
The hippopotamus’s skin is extremely sensitive and prone to drying out. For this reason, they like to stay in the water or roll around in the mud to keep their delicate skin moisturized. However, they are also very territorial creatures, and they will sometimes venture onto land to chase predators or other intruders out of their domain. In those cases, their mucus acts as further protection and lubrication for their skin until they can return to the water.
Sweating is an adaptation that helps dispel excess heat but it is relatively rare in the animal world. Here are seven animals that share this ability with humans:
|3||Old World Monkeys|
|7||Horses and Donkeys|
Thank you for reading! Have some feedback for us? Contact the AZ Animals editorial team.