Squirrels scream when they are extremely frightened. Ground squirrels emit a scream that is so high-pitched that humans can't hear it, alerting other squirrels of danger. The four main categories of squirrel communication are nesting, mating, aggression and warning calls.
Baby squirrels call to their mothers using sounds that resemble little sneezes. Baby squirrels use a high-pitched scream when they feel threatened, to alert their mothers. When a squirrel is aware of danger, it waves its tail. If the source of danger is still approaching, squirrels let out warning calls to other squirrels. They also use chattering sounds to communicate.