How do dolphins see with sound?
A dolphin can find its way, and its food, even if it is completely blind, by listening to the echoes of its own clicks.
▶ Start the storyDolphins and other toothed whales see with sound. They send out focused clicks, then listen to the echoes that bounce back from fish, rocks and the seabed. By timing the echo, the animal works out how far away something is, and it needs no light to do it.
The idea is simple: ranging works by measuring the time between the animal's own sound and the echoes that return. Underwater, it is a sensible trick, because vision is often extremely limited in range there, while sound travels well. Echolocation is the primary sense of toothed whales, which can survive even if completely blind.
The clicks come from the head. Air is passed through structures called , and the beam is focused by the , a large fatty organ on the forehead that acts as an acoustic lens. As the animal approaches something interesting, the click rate increases, so the picture gets sharper as it closes in.
Step 1: Air through the
Makes a high-frequency click
Step 2: The aims the beam
A fatty acoustic lens focuses the sound
Step 3: Echo returns from the target
Timing gives distance
Step 4: Jaw fat catches the echo
Passed on to the middle ear
The echoes do not come back through the ears alone. They are received mainly through fatty structures around the lower jaw, which pass the sound on to the middle ear. So the dolphin, in effect, hears with its jaw. Toothed whales generally hear frequencies, far above what a person can hear.
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Recap
Toothed whales click, listen for the echo and time it, like a sonar built into the head.
💡 A trick to remember it · Click out, jaw in: the melon aims the shout, the jaw catches the echo.
Surprising fact · Echoes are received mainly through fatty tissue around the lower jaw.
Sources (2)
No source, no claim. Every fact in this lesson (17 claims) cites at least one of these.