DIRECTORY TO SPECIES ACCOUNTS
LARGE WHALES
(40-85 feet [12-26 m] maximum overall length)
With a Dorsal Fin
All five species of large whales with a dorsal fin belong to the same major baleen whale group, the balaenopterid whales or rorquals. All are characterized by the presence of a series of ventral grooves, usually visible on stranded specimens and the length and number of which are diagnostic to species. In addition, all species, with the exception of the humpback whale, have at least one distinctive (though often not prominent) ridge along the head from just in front of the blowhole to near the tip of the snout. (The humpback whale, on the other hand, is distinguished by numerous knobs, some of which are located along the line of the head ridge, with others scattered on the top of the head.) In Bryde's whale, the single head ridge characteristic of the other rorquals is supplemented by two auxiliary ridges, one on each side of the main ridge.
At sea, these whales often appear very similar and must be examined carefully before they can be reliably identified.
In general, though the characteristics of behavior may vary from one encounter to the next, based on the activities in which the animal is engaged, whales in this group may be distinguished from each other on the basis of differences in 1) the size, shape, and position of the dorsal fin and the timing of its appearance on the surface relative to the animal's blow (in general, the larger the whale, the smaller the dorsal fin—the further back its position and the later its appearance on the surface after the animal's blow); 2) the height of body in the area of the dorsal fin, relative to the size of the dorsal fin, which is exposed as the animal sounds; 3) sometimes the blow rate and movement patterns; and 4) the shape and color of the head.
Despite variability in behavior by members of the same species from one encounter to the next, an observer can greatly increase the reliability of his identification by forming the habit of working systematically through a set of characteristics for the species rather than depending on any single characteristic.
Blue whale
Balaenoptera musculus
p. [19]
- Body very large, up to 85 feet (25.9 m) long.[7]
- Body basically bluish with mottlings of grayish white.
- Baleen all black.
- Head broad and nearly U-shaped, viewed from above.
- Head flat in front of blowhole, viewed from side.
- Dorsal fin small (to 13 inches [33 cm]), triangular to moderately falcate, in the last one-third of back.
- Distribution primarily from temperate seas to pack ice; rare in tropics.
- Distribution more northerly during summer.
- Flukes occasionally raised slightly on long dive.
[7] These figures are all near maximum sizes recorded for the North Atlantic. For all species which have historically been exploited by whale fisheries present maximum sizes may be significantly less than these figures.