Did you know that the pig is rated the fourth most intelligent animal? Pigs are part of the order artiodactyl. There are more than 180 species of pigs, found on every continent except Antarctica. They come in just about any size and color, have an average lifespan of 20 years and litters from 2 to 12 piglets. Pigs are often thought to be dirty, but actually keep themselves cleaner than most pets. They are seen laying in mud because they do not have sweat glands and constantly need water or mud to cool off.