THE ANIMAL FILES

Great hammerhead

Sphyrna mokarran

The broad head senses prey; the tall dorsal fin can help during rolled swimming.

The great hammerhead has an expanded head with a nearly straight front edge and a tall sickle-shaped first dorsal fin. These structures are involved in sensing, movement and the handling of prey.[1]

Follow the evidence ↓
Great hammerhead
Image: Josh Hallett from Winter Haven, FL, USA · Commons · CC BY 2.0
Head
Broad cephalofoil with a near-straight leading edge[1]
Food
Fishes, rays and invertebrates[1]
Posture
Can swim with the body rolled sideways[1]

Searching across the seabed

Electroreceptive organs on the broad head help detect signals from animals, including rays hidden in sediment. Sweeping the head over the bottom brings the sensing surface across potential prey.[1]

A head also handles prey

Observed attacks have included pinning a ray against the bottom with the head before biting. These records suggest a handling role in addition to sensation, without requiring every hunt to follow the same sequence.[1]

Rolling changes fin function

Accelerometer studies recorded sideways swimming. In that posture the large dorsal fin contributes to lift, and the study associated the behaviour with reduced drag and movement costs. Body orientation changes how a fin meets the water.[1]

A COMMON MIX-UP

Is the hammer-shaped head only a visual label?

No. It carries sensory structures and has been observed participating in prey handling.[1]

TRY A LITTLE REASONING

Why record body angle as well as swimming speed?

Reveal the explanation

Rolling changes which fins contribute lift and how drag is produced, so equal speeds need not imply equal swimming mechanics.[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 — Great hammerhead (fixed revision; adapted and translated)
  2. NCBI Taxonomy — Sphyrna mokarran (identity and classification)

Last fact check:

One discovery leads to another

Blue sharkBlue above, pale below: an ocean swimmer has more than one colour.Prionace glauca ↗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 ↗