How Does a Bat See in the Dark?

Sound Waves

Like dogs, bats can hear high-pitched sounds that humans and many other animals cannot perceive. Since the bats don't have the luxury of dog whistles, they have to make these sounds themselves. They create incredibly loud and high pitched sounds either through their mouths or noses. These sounds can often be so loud that the bat has to have a protective mechanism in its ears that contracts a muscle, closing off the ears to avoid damaging them.

Echo

Once the bat emits these sounds, it listens for an echo to come back. Based on the sound of the echo and where it's coming from, the bat is able to tell the shape of its surroundings and locate any prey on the premises easily. The echo will pick up even the tiniest bit of movement, such as the flutter of a fly's wing. This is important for the bat since insects are its main food source.

Picture in its Head

The bat has such a sophisticated sonar system that it can even pretty accurately gauge the size and shape of objects that it cannot see and even the density. It does this by listening not just to the sounds that echo back, but the way in which they echo back. This gives the bat a picture in its head which is not too different from what a human would see if wearing infrared goggles. This is why it appears that the bat is seeing in the dark.

Smell

One bat that does not have the ability to "see" in this manner is the Old World fruit bat. However, since these bats' prey is pretty stationary, this talent is generally not needed. Instead fruit bats have bigger eyes than their insect-eating brethren; however, they still require a decent amount of light to see well. When in doubt, this bat relies on its sense of smell to find fruit to eat.