Predator Fieldnotes · Sharks, without the spectacle
A shark does not navigate by smell alone. It brings together signals from its eyes, ears, skin and specialised sensory organs to make sense of the water.
These simplified diagrams show where signals are detected—not how far every shark can detect them.
Nasal openings sample water for dissolved chemical cues. They are separate from the breathing system.
Currents, turbulence and the strength of a source affect what a shark can detect. There is no universal “drop of blood” distance.
A system of sensory structures along the head and body detects local water movement.
It can provide information about nearby animals and the surrounding flow, complementing other senses.
Specialised organs detect weak electrical fields, including those produced by other animals.
This sense can help locate prey at close range, even when the animal is partly hidden in sediment.
Swimming and breathing are related—but not in the same way for every shark.
Forward motion sends water through the mouth and over the gills. Some species depend on this flow to obtain enough oxygen.
It helps explain why certain sharks keep moving, but cannot explain the behaviour of every species.
Other species can pump water across their gills while stationary. Some bottom-dwelling sharks also draw water through openings called spiracles behind the eyes.
A nurse shark resting on the seabed is still ventilating its gills.
Every advantage comes with a context.
MovementStreamlined bodies and powerful tails suit active swimming. Other body shapes support life close to the seabed. Fin arrangement and tail shape are useful clues, not a complete description of behaviour.
BuoyancySharks lack the gas-filled swim bladder found in many bony fish. An oil-rich liver contributes to buoyancy, while body structure and lift during swimming also play a part. Many sharks remain negatively buoyant.
These are introductory explanations. Sensory performance and swimming mechanics vary between species.
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