THE ANIMAL FILES

Blue shark

Prionace glauca

Blue above, pale below: an ocean swimmer has more than one colour.

A blue shark’s long pectoral fins and slim body make a distinctive outline in open water. Its back is dark blue and its belly white, and squid are important among its varied prey.[1]

Follow the evidence ↓
Blue shark
Image: Diego Delso · Commons · CC BY-SA 4.0
Body pattern
Dark blue above and pale underneath[1]
Swimming outline
Slender body with long pectoral fins[1]
Important prey
Squid and other marine animals[1]

A name that describes one side

The blue shark is deep blue along the top, lighter on the sides and white below. This countershaded pattern means a side view, a view from above and a view from underneath will not show the same appearance. Long pectoral fins add another useful feature beyond colour alone.[1]

Open water includes a vertical dimension

Blue sharks occur in temperate and tropical oceans, using surface waters and deeper layers. In temperate areas they may approach coasts, while tropical records can involve deeper water.[1]

Slippery prey and a varied menu

Squid are an important part of the diet, alongside bony fish and other marine animals. Triangular teeth help hold slippery prey.[1]

A COMMON MIX-UP

Is a blue shark blue from every viewing angle?

No. Its darkest colour is on the upper body, while the underside is white. The common name is a useful starting point, not a complete description of the animal’s three-dimensional appearance.[1]

TRY A LITTLE REASONING

What information does a surface map leave out?

Reveal the explanation

Depth. Blue sharks can occupy different water layers within their ocean range. Two observations at similar coordinates may still describe different conditions if one animal was near the surface and the other much deeper.[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 — Blue shark (fixed revision; adapted and translated)
  2. NCBI Taxonomy — Prionace glauca (identity and classification)

Last fact check:

One discovery leads to another

Tiger sharkSlow cruising does not reveal the whole hunting repertoire.Galeocerdo cuvier ↗Bull sharkEntering a river requires a shark to change how it handles salt and water.Carcharhinus leucas ↗Great hammerheadThe broad head senses prey; the tall dorsal fin can help during rolled swimming.Sphyrna mokarran ↗