The expression “blind as a bat” is not an accurate simile. Studies suggest that bats rely on visual landmarks just like birds do. Unlike birds, bats are mammals. The only mammal in the world that can fly is the bat. Some species of bats fly about rapidly when hunting for insects. This may be where the misleading expression comes from. It is true that bats don’t have strong night vision. Nocturnal bats rely on a sonar system called echolocation. They deliver a high-pitched call and wait for an echo. The echo tells the bats how far away they are from an object. This helps bats find their way around at night. It also helps them catch their prey. Not all bats are nocturnal, though. Large fruit bats don’t live in caves and actually like the daylight. Only a few of more than 1000 species of bats feed on blood.