Level of interest - at night is the best time to watch mice as they play, run, etcc.... they are ever so fun to watch as they are very acrobatic and hang from the bars at the top of the cage. So they are very interested in everything.

Facial expressions - Depending on how well the mouse is taken to the owner they have many facial expresions, I have a mouse that smiles at you when you first wake up in the morning, she also has a sad face, a frightened face and even an inquisitive face. Can get pictures of the different face types if needed

Body postures - When a mouse is relaxed it will start cleaning itself, Frightened it will start banging its tail on the side of its cage while being as still as possible, and when it is wide awake and looking for trouble it will stand on its to back paws and look around for some where it can cause trouble.

Vocal and olfactory signals (isn't this sniffing? lol) - Yes mice do do a lot of sniffing of each other, but they also squeak when the dominant one is putting a naughty mouse back in line, also squeaking can happen when they are fighting over a bit of food. There is also a little squeaking sound or tuttering as I put it, when they are happy, you can normally hear this if you put the mouse to your ear.

Interaction with other animals - Well I recently had Callie my mouse get out and get into a gerbil cage, and I found them sleeping together they also play and eat together. When the cats are around mine are always at the bars sniffing the cats. Even the rabbits get checked out when they come by the cage.