Rats! Some people hate them as pests and others keep them as pets. This is a domestic, pet rat. Domesticated rats are usually very friendly. All rats are cautious and intelligent.
Rats, unlike other mammals, can't vomit. So they're very careful about what they eat, not trying new things until they're sure they are safe. Rats primarily want grain, in the wild, and will swarm on crops when they start to ripen.
They're very social, and will even set other rats free from cages. They tend to live in large colonies, and in some areas can breed until they swarm in a "plague" of rats.
I've both cursed at city rats, and cooed gently to pet rats.