Hippos Sweating Blood!
Hippos don't have sweat glands, instead they have glands that produce a red-colored secretion that acts as a sunscreen and inhibits bacterial growth on the skin. This secretion is often mistaken for blood, giving rise to the misconception that hippos sweat blood.
Sweating, or perspiration, is a secretion from the sweat glands present in the skin of many mammals. It is mostly an act of thermoregulation.
Thermoregulation is the ability of the body to maintain its temperature. Sweat usually evaporates from the surface of the skin and helps to cool off the body whenever it gets heated. That is the reason why we sweat on hot summer days or while physically exerting ourselves.
There are, however, many animals that don't really sweat, some of them regulate their body temperature by panting. This helps in dissipation of heat from their mouth. Now, let us get right down to business and find out whether pigs really sweat or not.
Do Pigs Sweat?
Contrary to the popular belief, pig don't really sweat much. An average adult human may produce 2-4 liters of sweat per hour, compared to that the sweat produced by a pig is almost negligible. This is because porcine skin has very few sweat glands.
This trait is not unique to these animals, dogs don't sweat much either. They maintain their body temperature by panting and sweating through their paws. But unlike a dog, you will never find a pig panting, so how is it that a pig can maintain its body temperature?
With obvious innate thermoregulatory mechanisms absent, maintaining body temperature for these animals can be a bit difficult, especially because they cannot tolerate a temperature above 22°C. Pigs have overcome this challenge by evolutionarily developing an affinity for wallowing in mud. This helps to reduce their body temperature when their ambient temperature is pretty high. This is why you'll find them rolling around in mud (and you thought they were filthy to do so). Apart from pigs, other animals like rhinos and elephants are also seen to regulate their body temperature by covering themselves with mud or water.
Is It Safe to Eat Pork?
The fact that pigs don't sweat has led people to believe that there must be a buildup of toxins in pigs, and so it might not be safe to eat them. If you have given up on your beloved bacon listening to this, then it's time to be happy again, as pork doesn't contain these so-called toxins!
The primary function of perspiration in mammals is regulation of body temperature, elimination of certain toxic molecules may be an added advantage. Elimination of toxins is more of a job for the liver and kidneys. As the organ system in pigs is well-developed, elimination of toxins takes place quite efficiently.
Sweat Like a Pig!
"Sweating like a pig" usually means to sweat profusely. Now that we've established that pigs don't sweat, we need to debunk what on earth made pigs infamous for sweating. The origin of this idiom lies far from the animal kingdom, it has evolved from the process of smelting iron. When molten iron is poured into runners made of silica and allowed to cool, the shape it takes after cooling kinda resembles a sow and her piglets. This gives the iron its name, pig iron (talk about imagination).
When pig iron cools the air surrounding the metal reaches its dew point leading to the formation of droplets of moisture on the surface of the metal. Thus, the idiom "sweating like a pig" came into existence.