Here is a list of actions you hamster might make and reasons for them.
Squeaking:
Your hamster is frustrated, angry, or hurting; it is best to return your hamster to its cage. Check to see if your hamster shows any sign of illness.
Although this says that a hamster squeaks due to being threatened I saw one site that said that it is a mating call. Another site said it means it is happy. So I guess it can squeak at any time. It's normal though. All the hamsters that I have had also squeaked but sometimes they were playing sometimes they may have felt threatened. One of my hamsters even squeaked whenever he wanted to be held. Just observe the way it is acting. Read its body language and maybe you'll know what emotion he is trying to show!
Source(s):
Experience with my hamsters and google!!!!!
