Eventually, the babies get too heavy and the mothers leave them 'at home' at the roost, whilst they go off to find fruit for themselves. At this stage, the young are still feeding on mother's milk. When the young can fly, then they go off in search for their own food, although they may stay close to mother for guidance. Echo-location is something that bats use to help them find their way about. Many bats have huge ears like radio dishes to help them hear the sound better.
Bats can interpret what the echo means.
When bats are flying they make thousands of sound bleeps a minute, but when they are resting, they hardly make any.