THE ANIMAL FILES

Basking shark

Cetorhinus maximus

A giant open mouth can be a plankton filter rather than a large-prey trap.

Basking sharks feed by swimming forward with the mouth open. Gill rakers retain small prey from the passing water. Large size and a familiar shark outline coexist with a feeding system centred on dense patches of zooplankton.[1]

Follow the evidence ↓
Basking shark
Image: Greg Skomal / NOAA Fisheries Service · Commons · Public domain
Feeding mode
Ram filter feeding[1]
Food
Zooplankton, especially copepod-rich patches[1]
Teeth
Small teeth, not a toothless mouth[1]

Water through a moving filter

Forward movement drives water into the mouth and across the gill-raker system. Tiny organisms are retained while water passes out. Copepod-rich patches are favoured, so the animal is not sampling every parcel of sea equally. Prey concentration helps determine where feeding effort is worthwhile.[1]

The outline does not dictate the meal

Long gill slits, a wide mouth and small teeth differ from the large cutting teeth of a white shark. A basking shark still has teeth, but filtering is the important food-acquisition mechanism. Anatomical details therefore distinguish two sharks whose distant silhouettes might initially look similar.[1]

Hidden travel and visible leaps

Satellite tags reveal journeys over thousands of kilometres and long periods below the surface. The species can also breach, although proposed reasons remain uncertain. A rare spectacular leap should not replace tracking data when describing ordinary movements, and absence from the surface does not establish absence from an area.[1]

A COMMON MIX-UP

Is a filter-feeding shark necessarily toothless?

No. Basking sharks have small teeth alongside the gill-raker feeding system.[1]

TRY A LITTLE REASONING

Why seek a dense plankton patch instead of filtering all water equally?

Reveal the explanation

More prey per volume of water can increase food obtained during forward swimming.[1]

Sources & editorial notes

Adapted and translated from the cited Wikipedia revisions, with source-linked reasoning. Image credit and licence are listed separately above.

Adapted and translated from Wikipedia contributors; exact revisions are linked below. CC BY-SA 4.0

  1. Wikipedia contributors — Cetorhinus maximus (adapted and translated; exact revision)
  2. NCBI Taxonomy — Cetorhinus maximus (identity and game lineage)

Last fact check:

One discovery leads to another

Common thresherThe tail joins the hunt.Alopias vulpinus ↗Great white sharkA long journey can run on reserves in the liver.Carcharodon carcharias ↗Goblin sharkThe jaws reach forward before the whole shark needs to.Mitsukurina owstoni ↗