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ELI5 Yahaaa

Senses you do not have

How Does a Shark Find Its Food?

A shark can smell a trace of blood in a huge amount of water, and feel the faint electric buzz of a fish hiding in sand.

Smell that follows atrailA line down each sidethat feels ripplesJelly-filled pits thatsense electricityTeeth in rows, alwaysmoving forward
A shark is mostly senses, wrapped in muscle.

  1. Step 1 of 5

    It smells its way along a trail.

    1 A trace driftsaway on thecurrent2 One nostrilsmells morethan the other3 It turnstowards thestronger side

    Water carries smells the way air does. A shark swings its head side to side, comparing which nostril smells more, and turns towards the stronger side until it arrives.

  2. Step 2 of 5

    It feels ripples with its sides.

    A fish thrashes Its side linefeels the push

    A line of tiny hair cells runs down each flank. A struggling fish sends out pressure waves, and the shark reads them like you read a nudge — it knows where and how far without seeing anything.

  3. Step 3 of 5

    It senses electricity.

    Dark speckles on thesnout Pits that read aheartbeat through sand

    Every moving muscle makes a faint electric field, including a heartbeat. A shark's snout is dotted with jelly-filled pits that pick this up — so a flatfish buried in sand is not hidden at all.

  4. Step 4 of 5

    Its teeth are on a conveyor belt.

    1 A front toothbreaks off2 The row behindrolls forward3 A new rowstarts growingat the back

    Shark teeth are not rooted in bone, so they fall out constantly. A fresh row is always waiting behind, and it rolls forward to take the place — a shark can get through thousands in a lifetime.

  5. Step 5 of 5

    A shark really is a fish.

    A whale Lungs, warm blood,bonesA shark Gills, cold blood, nobone at all

    Unlike a whale, a shark takes its air from the water through gills and never surfaces to breathe. Its skeleton is not bone at all — it is rubbery cartilage, the same stuff as the tip of your nose.

    Shark skin is covered in microscopic teeth that all point backwards. Stroke it one way and it is smooth; the other way it is like sandpaper.

The short version

A shark hunts with smell, with ripples felt along its sides, and with pits that read the electricity of a heartbeat.

Try it yourself

Close your eyes and have someone clap once in the room. Pointing at the sound is the same trick as a shark comparing its two nostrils.

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