How do sharks find prey in dark water: smell, electric sense and pressure?
A shark can pick up the faint electric field of a hidden fish through the skin of its snout: an organ described in 1679 whose job nobody understood for almost three centuries.
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Which one is it?
A shark finds prey by combining several senses, and three of them work even when the water is too dark or too murky to see. It smells, it feels water movement, and it can detect the faint electric fields that every living animal gives off.
Step 1: Smell
Parts per million of blood, with direction from nostril timing.
Step 2:
Feels water speed and pressure changes nearby.
Step 3: Electric sense
Ampullae of Lorenzini pick up the fields that muscles produce.
Smell comes first. Some sharks can detect as little as one part per million of blood in seawater, and they work out which way a scent is coming from by the timing of its arrival in each nostril. In low-visibility waters, sharks generally have larger , the part of the brain that handles smell.
Close in, a shark feels the water. Its is a system that detects water speed and pressure changes nearby, and it helps the shark sense currents, obstacles and struggling prey that it cannot see.
The strangest sense is electric. Every animal produces an electrical field through muscle contractions. Sharks have called ampullae of Lorenzini, with pores concentrated around the snout and mouth. Sharks are more sensitive to electric fields than any other animal, and it lets them find prey hidden in sand. The organs were described in 1679, but their job was only identified in 1960.
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A signal fades with distance
y = 100 · x^−1
Challenge · Keep the strength at 100 and choose the exponent so the signal at distance 2 is a quarter of the signal at distance 1.
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Recap
A shark can smell, feel pressure and sense the electric field of living muscle, so even hidden prey leaves clues.
💡 A trick to remember it · Nose, wake and spark: smell the trail, feel the ripple, sense the muscle's electricity.
Surprising fact · The ampullae were described in 1679, but only identified as electric-field sensors in 1960.
Sources (2)
No source, no claim. Every fact in this lesson (14 claims) cites at least one of these.