Blue Whale

Balaenopterra musculus

The blue whale is the largest animal ever to have lived on Earth. Its body is very long, tapered and streamlined. The head is broad, long and almost U-shaped, accounting for up to a quarter of the animal’s total length. A single prominent ridge runs from the tip of the rostrum to just forward of the paired blowholes, which are contained in a large, raised splash guard. The body is smooth and relatively  free of visible parasites, though a few barnacles may attach themselves occasionally to the edges of the flukes and the tips of the flippers. Between 55 and 88 throat pleats

Key  Characteristicsblue whale

  • Exceptionally long body
  • Longitudinal ridge on head
  • Blue-grey body color
  • Light -grey mottled appearance
  • Tiny, stubby fin set far back
  • Broad, flattened, U-shaped head
  • Large blow holes with splash guard
  • Extremely thick peduncle
  • Blow 9-12 m, vertical

Dorsal Fin: about 30cm high, thus very small in proportion to the body but readily observable at sea. Its shape may be triangular or falcate. The tip may be rounded or pointed. The fin is located about three-quarters of the distance along the body from the head.

Flippers: tapered and relatively short, about eleven percent of total body length.

Flukes: broad, triangular and up to 25 percent of body length in span. The rear edges are smooth and slightly concave, with a marked median notch. Variations in the shape of the flukes aids photographic identification of individual animals, as do the patterns of mottling on their flanks.

Baleen Plates: between 260 and 400, black in colour, suspended from either side of upper jaw. Length 50cm (front) to 100cm (rear).

Colouration: blue-grey, often with lighter grey mottling on a relatively dark background (or the reverse). The underside is paler, sometimes white, though microorganisms growing on the skin sometimes cause it to take on a yellowish-green tint. The leading edge or underside of the flippers may be of a lighter colour or white, while the flukes are dark underneath.

Behaviour: Blue whales are fast, strong swimmers, cruising at about 20km/h (11kt), and capable of reaching speeds of 45km/h (25kt) when alarmed. Feeding speeds are slower, usually 2-6km/h (1-3kt). They can sometimes be easy to approach. Adults, unlike their young, rarely if ever breach.

Blowing and diving patterns vary according to the type of activity in which the whale is engaged. ‘Flukes up’ indicates a deep dive. Shallower dives are ‘flukes down’ or ‘no fluking’. When relaxed, the whale will spout 1-4 times a minute for a total of between two and six minutes before diving. Dives last from less than ten minutes to up to half an hour, the longer times signifying deeper dives. Blue whales spend more than 94 percent of their time submerged. After a deep dive, a blue whale will reoxygenate its body by blowing, i.e. breathing, 5-12 times a minute.

Blue whales feed all day but are less active in the afternoon. Fluke-up dives are common when feeding. They approach prey from beneath, lunging upward through the prey field with open mouths, often swimming on their sides or upside-down.

Group Size: usually solitary or in pairs, though groups of up to six are sometimes found together. Aggregations of up to 25 may gather in feeding areas.

Associates: known to associate with Bryde’s whale in feeding areas.

Diet: crustaceans, mainly euphasiids (krill) and mysids.

Dive Depth: 300-500m

Blow: 9-12m, vertical.