Whales, Dolphins, and Porpoises of the Western North Atlantic Part 3

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 k.n.o.bs, 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.

[Sidenote: 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.

[Footnote 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.

It should also be noted that differences in methods of measurements often account for discrepancies in reported lengths.]

[Sidenote: FIN WHALE

_Balaenoptera physalus_

p. 26]

Body large, up to 79 feet (24 m) long.

Body mostly dark gray or brownish gray; undersides of flukes and flippers and belly white; grayish-white chevron frequently on back behind head.

Right lower lip white; right upper lip sometimes white; left lip dark.

Head V-shaped, viewed from above.

Right front one-third to one-fifth of baleen plates, yellowish white.

Other baleen bluish gray with yellowish-white stripes.

Dorsal fin to 24 inches (61 cm), slightly more than one-third forward from tail; forms angle of less than 40 with back.

Distribution extensive but not very common near pack ice and in tropics.

Distribution more northerly during summer.

Flukes not raised on dive.

[Sidenote: SEI WHALE

_Balaenoptera borealis_

p. 32]

Body up to 62 feet (19 m) long.

Body appears s.h.i.+ny; dark gray on back, often with ovoid grayish-white scars; white on front of belly; undersides of flippers and flukes dark.

Baleen grayish or ash black with fine, light-gray bristles.

Dorsal fin to 24 inches (61 cm), strongly falcate, well more than one-third forward from tail; forms angle of more than 40 with back.

Distribution extensive; are not very common in cold waters and may have a greater tendency than fin whales to enter tropical waters.

Distribution more northerly in summer.

Flukes not raised on dive.

[Sidenote: BRYDE'S WHALE

_Balaenoptera edeni_

p. 37]

Body up to 46 feet (14 m) long.

Body dark gray overall.

Head has series of three ridges from area of blowhole to snout.

Baleen slate gray with coa.r.s.e dark bristles.

Dorsal fin to 18 inches (45.7 cm), falcate, well more than one-third forward from tail, often irregularly worn on rear margin.

Distribution primarily tropical and southern temperate.

Flukes not raised on dive.

[Sidenote: HUMPBACK WHALE

_Megaptera novaeangliae_

p. 40]

Body up to 53 feet (16.2 m) long.

Body dark gray with irregular white area on belly; flippers white; underside of flukes often has varying amounts of white.

Head in front of blowhole flat and covered with k.n.o.bs.

Baleen dark gray to black with olive-black bristles.

Dorsal fin small, quite variable in shape, usually hooked, located on a step or hump, in last one-third of back.

Flippers very long (to nearly one-third of body length), white, and scalloped on leading edge.

Distribution at least New England to Iceland and Greenland during summer.