When temperatures soar, people often exclaim that they are ‘sweating like pigs’, although this expression has little to do with pigs at all. As pigs are mammals, thermoregulation (the ability to keep one’s body temperature at a certain level) is important and while they do have a few sweat glands, they are mostly ineffective at keeping them from overheating.
Instead, pigs have had to find another way to cool down in the heat. Sweat keeps us cool as the water evaporates from the surface of our skin. To compensate for a lack of sweat glands, pigs take to rolling around in water or mud, which has the same cooling effect.