According to a 2008 study, mice squeak to communicate, portray emotion and exhibit reward-seeking behavior. Mice rely strongly on hearing to communicate while away from the nest and gathering food.
Humans cannot hear all the squeaks a mouse makes because of its ability to make audible and ultrasonic sounds. Male mice create complex patterns with their squeaks during reproduction. Females chirp while around other females, and mouse pups squeak when their mothers leave. Scientists involved in this study related the squeaks to dopamine, or pleasure-seeking behaviors. Dopamine-deprived mice were less vocal overall, indicating that mouse squeaks are related to experiencing and searching for pleasure.