Do Dolphins And Whales ‘See’ With Sound?

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While it is not feasible to believe that we can fully understand how another species perceives the world, researchers have devised tests which show that bottlenose dolphins (cousins to the orcas) have the ability to correlate the information from their sonar with what they see, as demonstrated by the following two video clips.

The first one shows that a dolphin can match an object that it can only detect with sonar, with one that it must use vision to perceive:

The second clip shows that dolphins can then remember an object, with an associated “word”:

So we know that at least some cetacean species can detect objects with their sonar and refer to them visually, but to determine whether or not this means that they truly ‘see’ a picture of the object with their sonar we need to find out if there is a biological format that would enable them to do this. The evidence is definitely there.

First, their brains are constructed such that their visual and hearing pathways are developed to make this possible. Their brains are different from ours, things are moved around and different regions are enhanced, but scientists have shown that there is a system in place that would make visualizing sound feasible (for those of you who want a challenging, but clearly written summary of this subject, I recommend Dolphin Biosonar Echolocation A Case Study by James T. Fulton).

Second, their bodies are equipped to take in sound information from several directions at once, which would help them to build a three dimensional picture of an object due to the time difference of the returning signal. Even their teeth are arranged asymmetrically – and although there is speculation that the teeth actually act as antennae of sorts, I think it could also be true that the tooth placement is a byproduct of how the jaw beneath transfers the sound information.

Sperm whale jaw (Creative Commons)

Look carefully at the picture on the left and you can see how the teeth on the left and right sides of the jaw are offset from each other. Note also the dish shape of the skull – the brain actually sits behind this dished area; nestled in front was the ‘acoustic lens’ composed of fats and oils that the whale used to focus the sound beam. Sperm whales such as this one have a particularly fine grade of oil, and were ruthlessly exploited for this in the past.

Finally, returning to our vision analogy from the previous post, scientist have shown that the way we process what we see is also complicated, involving special cells, nerve pathways and dedicated regions of our brains – and by time the information reaches the brain it could have come from any type of sensory input. In the case of cetaceans, being able to “see” what they “hear” is the most efficient way to process the information.

Next: How might cetaceans have evolved this ability?

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