The craving for salt, both by animals and human beings, is one of the most interesting mysteries of nature. We know that for thousands of years salt has been used and valued by man. Our word "salary" comes from that was so important that a beautiful maiden was sacrificed to the salt god every year. And we know that today, when a prisoner in jail is deprived of all salted food, he practically goes crazy with desire for it.
The fluid in our body, the liquid part of it, is a salt solution. And since our body continuously eliminates liquid in many ways, including perspiration, it must make up for this loss of salt.
Now while there is enough salt in the oceans to cover the whole surface of the earth, the land part of the world is poor in salt. Plants do not contain much salt, and most of the salt in the land itself is washed off by rain water into rivers and oceans.
Land animals, however, are descended from creatures that used to live in the sea. Their body fluid is still what it used to be before they moved to dry land. This means that their body fluid is still like sea water! And since neither plants nor the land can give them enough salt, they keep craving for more and -love to eat salt.
Carnivores, or animals who eat meat, do not crave salt. This is because they obtain it from the body fluid of their victims. But herbivores, or animals who live on vegetable matter, need more salt and love to eat it.