As we enter the dog days of summer, people will try all sorts of things to escape the heat, from sweating in front of a fan to drinking a piping hot cup of tea (which actually does help). But body heat is about more than comfort—it's a question of survival. Rising body temperature puts more stress on various functions, for instance, increasing blood flow and putting strain on the heart and brain. With global temperatures consistently hitting record highs, how efficiently an animal can keep cool could spell the difference between existence and extinction.
When it comes to our natural method of regulating body temperature, humans are among the only animals in the world who cool down by perspiration. But our scaled, furred or feathered friends aren't left to suffer helplessly in the heat. Some creatures have evolved unique—and sometimes disgusting—adaptations to deal with scorching temperatures.
Sweating might be the most familiar way to cool down, mainly because it's the favored method of humans. Sweat is made mostly of water with some potassium, salt and other minerals. As it evaporates from the skin, it carries heat away and reduces your overall body temperature. Sweat is produced in sweat glands, which are activated by the hypothalamus, the area of your brain that controls certain key biological processes, including your heart rate, your blood pressure and your body temperature. The average human body has between two and five million sweat glands.
Humans aren't the only animals with sweat glands, but we are one of the few species that produces large amounts of perspiration to cool off. While sweating might lead to awkward encounters on a hot day, some scientists think that it also gave us an evolutionary advantage. Daniel Lieberman, professor of Human Evolutionary Biology at Harvard University, argues that our ability to sweat let us run longer distances at faster speeds than other animals. This meant humans could hunt game during the hottest parts of the day, when other predators were forced to rest. Other experts, such as anthropologist Nina Jablonski at Pennsylvania State University, say that sweating provided more efficient cooling that allowed us to evolve bigger, hotter brains.
In addition to higher primates (monkeys, apes and humans), horses are among the only other animals in the world that perspire profusely—making them one of the few that could challenge humans in a marathon.