Using high-pitched squeaks beyond the limits of human hearing, bats navigate and locate prey in the dark by interpreting the echoes produced when their calls bounce off objects, a technique called echolocation. Even if humans could hear in that range, the idea of locating a creature as tiny as a mosquito strictly by the sound which bounces off its body hints of science fiction. Flying with their mouths open, bats emit a constant stream of cries. As the animal hones in on prey, the calls become more frequent -zot, zot, zot, zzzt. Thus bats ate basically shouting as loud as they can.
Bats use other hunting tools as well as echolocation.
Big eared bats listen for the footsteps and chewing sounds of feeding caterpillars and swoop down to pluck the insects off of vegetation. The vision of California leaf-nosed bats is equal to the best night vision scopes, allowing them to see insects feeding on vegetation. Stop-action photography reveals how bats corral elusive prey by cupping their wings and tail membranes to scoop insects towards their mouths. When winter arrives in the northern hemisphere, bats migrate to warmer climates, or find a quiet cave or shelter with constant temperature and humidity and enter a state of hibernation. This can result in the animal's starving before the end of winter.