Bat Sonar

Sometimes I think a bit about what it must be like to sense the world as a bat does. How on earth can we as human beings really understand what it must be like for a bat to sense its world in that way? This idea actually was part of a philosophical paper done years ago in 1974 by Thomas Nagel called, What Is It Like to Be a Bat? He essentially felt that it was impossible for us to fully understand what it must be like to be a bat because we have no common ways of communicating. Some folks have argued this differently since then, but to me, it seems very difficult for us as non-flying, large mammals with limited hearing abilities and no affinity for the night to understand what this would be like.

Our bats are out at night, and even though they have eyes, vision needs to be supplemented because it is dark. So bats developed an echolocation system that allows them to “see” into the dark of night by using sound and its reflections. This is sort of a land or air-based sonar.

Bat sonar 1I do think, though, that we might consider analogies that could help us understand this sonar/echolocation system. We can start with a depth finder (now called fish finders). Depth finders send out sonar or sound waves down into the water. The sound bounces off of objects back to the underwater transponder that picks up the signal. The results are computed and displayed on a screen. I remember when they first came out and about the only thing they could do was tell you the depth, hence the term, depth finder.

Now depth finders do so much more. They can tell you what the bottom is like, whether there are rocks, branches or mud, they can show you where fish are, including an estimate of how many, how deep and how large a group. Because they can now find fish, they are typically called fish finders.

Bat sonar fishfinderThe sounds bouncing off of objects in the water below could be played back for us to hear, but that would be pretty hard to understand. The fish finder unit translates the sonic information into visual information on its display. I am no expert on fish finders, but I do know they are capable of amazing detail of things underwater, showing a lot about the fish, and even small bait fish. They are also capable of dealing with false noise signals that create noise that can obscure details.

Bat sonar 2bOn a fish finder, moving objects show up as curves, which usually mean fish. But you can’t get much more detail. Some fish finders add little fish icons over these visuals to remind you that you are seeing fish.

Bat sonar fishfinder4Bats can do all this and more. And they don’t need any icon reminders!

Bats can use their echolocation to render detail as small as a human hair (different species have differing abilities as to how small a detail they can discern, but it is all close to that level). If they were a fish finder, they would actually see details of the fish, down to the fins. And they could tell the difference of a fish from a turtle or any other swimming object.

For me, though, the fish finder gives an idea of what a bat might “see” with its echolocation. Just imagine it far more detailed!