Bats do not actually cry in the sense that humans do. The sound we perceive as a "cry" is actually their echolocation calls.
Echolocation is a sensory system used by bats (and some other animals) to navigate and find prey in the dark. It involves emitting high-frequency sounds and then listening for the echoes that bounce back off of objects in the environment.
Bats use echolocation because they are nocturnal animals and need to navigate and hunt in the dark. Echolocation allows them to locate food, avoid obstacles, and find roosting sites in complete darkness.
Yes, humans can hear the sounds of bat echolocation, although some of their calls may be at frequencies that are too high for us to detect. Bats often emit calls at frequencies between 20 and 100 kHz, while the range of human hearing is typically between 20 Hz and 20 kHz.
No, bat cries are not harmful to humans. In fact, bats are generally not aggressive towards humans and will only use echolocation as a means of communication and navigation. Some bats may emit louder calls if they feel threatened, but they do not pose any danger to humans through their cries.