In the wild they live in very large groups. Sometimes they will even band with other groups. Baby rats are born through their mother's body. When babies are born, they have no fur and very thin skin. Baby rats are completely helpless, so their mothers stay with them for awhile.
Rats have a few interesting features.
I said earlier was that they band together to take down larger farm animals. Another thing, rats can carry up to 20 different diseases in the wild or ones that live at your house. These tiny animals which are actually moderate sized for rodents, can cause much damage and destruction. When they are tamed, they make good pets and they can be interesting to study and learn about.