THE ANIMAL FILES

Harbour porpoise

Phocoena phocoena

A small coastal hunter follows fish through the water column.

The harbour porpoise has a compact body, a triangular dorsal fin and a poorly defined beak. Its feeding is not restricted to one depth: prey near the bottom, in mid-water or near the surface can draw it to different places.[1]

Follow the evidence ↓
Harbour porpoise
Image: Ecomare/Sytske Dijksen · Commons · CC BY-SA 4.0
A compact outline
The dorsal fin is triangular.[1]
Following the prey layer
Feeding depth changes with prey.[1]
Coastal movement
Individuals can move between inshore and offshore waters.[1]

A compact outline

The body is thickest just ahead of the dorsal fin, with a dark back and paler underside. The beak is not strongly set apart from the head. These visible proportions are useful for recognising the animal, particularly when only a brief surfacing is seen.[1]

Following the prey layer

Small schooling fish provide much of the food, and squid or crustaceans are also taken in some places. Feeding may occur near the bottom in shallower water, nearer the surface for sprat, or in mid-water in deeper areas. The prey's location helps explain the porpoise's position.[1]

Coastal movement

Porpoises are often seen alone or in small groups. Some studies describe limited local movements, but recorded trips between inshore and offshore waters prevent a simple claim of permanent residency in one spot. A local sighting documents presence, not the full extent of an individual's movements.[1]

A COMMON MIX-UP

Must a harbour porpoise remain inside a harbour?

No. It uses several coastal settings and can move between inshore and offshore waters.[1]

TRY A LITTLE REASONING

Why might one animal feed near the surface on one occasion and deeper on another?

Reveal the explanation

Different prey occupy different layers. Following food can change feeding depth without changing species identity.[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 — Harbour porpoise (cited revision)
  2. NCBI Taxonomy — Phocoena phocoena

Last fact check:

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