2,271. Beginning Hilchos Maachalos Assuros
Maachalos Assuros 1:1
There is a positive mitzvah to know the signs that differentiate between kosher and non-kosher domesticated animals, wild animals, birds, fish and locusts as per Leviticus 20:25, “You shall distinguish between a kosher and a non-kosher animal, between a non-kosher and a kosher bird” and Leviticus 11:47, “To differentiate between kosher and non-kosher, between an animal that may be eaten and one that may not be eaten."
Maachalos Assuros 1:2
The signs of domesticated and wild animals are explicit in the Torah: split hooves and chewing cud. Both of these are necessary; any domesticated or wild animal that chews cud doesn’t have teeth on its upper jaw. Every animal that chews cud also has split hooves except for the camel. Every animal that has split hooves also chews cud except for the pig.