Whales, Dolphins, and Porpoises of the Western North Atlantic Part 4

Distribution to shallow tropical banks, winter and spring.

Flukes often scalloped on trailing edges and sometimes raised on dive.

NOTE: Because of its small adult size, usually less than 30 feet (9.1 m), another member of the rorqual family, the minke whale, is included with the medium-sized whales in this guide. Features by which it may be distinguished from all other rorquals are discussed in the species account.

Further, inasmuch as the dorsal fin of the humpback whale is highly variable in shape, positive identification may require reference to the sperm whale (p. 57), which, though the sperm whale has been cla.s.sified with species without dorsal fin, has a rather distinct dorsal hump, particularly noticeable when the animal arches the back and tail to begin a long dive.

[Ill.u.s.tration: Figure 8a.--Swimming, blowing, and diving characteristics of blue, fin, sei, and Bryde's whales.]

[Ill.u.s.tration: Figure 8b.--Swimming, blowing, and diving characteristics of humpback, bowhead, right, and sperm whales.]

(40-65 feet [12-20 m] maximum overall length)

Without a Dorsal Fin

There are three species of large whales without a dorsal fin in the western North Atlantic Ocean. Two of these, the bowhead or Greenland whale, and its more widely distributed close relative the right whale, are baleen whales. The third, the sperm whale, is a toothed whale. The first two have relatively smooth backs without even a trace of a dorsal fin. The sperm whale has a humplike low, thick, dorsal ridge, which, from certain views, particularly when the animal is humping up to begin a dive, may be clearly visible and look like a fin. But because the profile of that hump and the knuckles which follow it are often not very prominent in this species, it has been cla.s.sified with the finless big whales.

All three species are characterized by very distinctive blows or spouts.

In both the bowhead and the right whales, the projection of the blow upward from two widely separated blowholes a.s.sumes a very wide V-shape with two distinct columns, which may be seen when the animals are viewed from front or back. Though this character may be visible under ideal conditions in many of the other baleen whales species as well, it is exaggerated and uniformly distinct in the bowhead and right whales and may be used as one of the primary key characters. In the sperm whale, the blow emanates from a blowhole which is displaced to the left of the head near the front and projects obliquely forward to the animal's left.

This blow seen under ideal conditions positively labels a large whale as a sperm whale.

Remember, however, that wind conditions may affect the disposition and duration of the blow of any species and that a single character alone is seldom sufficient to permit positive identification.

[Sidenote: BOWHEAD WHALE

_Balaena mysticetus_

p. 49]

Body to 65 feet (19.8 m) long.[8]

Body dark; back smooth.

Chin and belly often white.

Head lacks callosities.

Baleen dark gray with gray fringes; to 12 feet (3.7 m) or more.

Upper jaw and lower lip strongly arched.

Two blowholes clearly separated.

Blow projects upward in wide V-shape.

Distribution restricted to Arctic waters south to Davis Straits.

Flukes raised on longer dives.

[Footnote 8: These figures are near maximum sizes recorded for the North Atlantic. All three species have been heavily exploited by whale fisheries. Therefore maximum sizes today may be significantly less than these figures (see text).

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

[Sidenote: RIGHT WHALE

_Eubalaena glacialis_

p. 52]

Body to 53 feet (16.2 m) long.

Body from dark to light gray and mottled; back smooth; chin and belly usually white.

Head and lower jaw covered with callosities (the largest of which is called the bonnet and is set on top of the snout).

Baleen usually dark gray with dark fringes; to 7.2 feet (2.2 m).

When animals swim, mouth agape, near surface; baleen sometimes appears pale brownish to yellowish gray in color.

Upper jaw and lower lip strongly arched.

Two blowholes clearly separated.

Blow projects upward in wide V-shape.

Distribution extends from Iceland south at least to Florida and reported from Texas.

Flukes raised on longer dives.

[Sidenote: SPERM WHALE

_Physeter catodon_

p. 57]

Body to 69 feet (20.9 m) long; males grow significantly larger than females.

Body dark grayish brown to brown; wrinkled in appearance.

Back has rounded hump followed by knuckles.

Head boxlike, comprises up to 40% of body length.

From 18 to 25 functional teeth in each side of narrow lower jaw.

Single blowhole on left of head at front.

Blow projects forward obliquely from head and to left.

Distribution extends from tropics to Arctic; adult males distributed farther north.

Flukes raised on longer dives.

MEDIUM-SIZED WHALES

(13-32 feet [4-10 m] maximum overall length)

With a Dorsal Fin

There are 11 species of medium-sized whales with a dorsal fin known from the western North Atlantic. These species, taking many diverse forms, range in maximum adult size from about 13 feet (4.0 m) (grampus) to about 33 feet (10.1 m) (the minke whale). This group includes such widely distributed and frequently encountered species as the pilot whales, false killer whales, and minke whales, and such rarely encountered and poorly known species as the various "beaked whales"

(_Mesoplodon_ spp. and the goosebeaked whale).

Aside from their common inclusion within the stated size range and the presence of a dorsal fin in all species (which ranges from only a small nubbin in some of the beaked whales to a substantial 5- to 6-foot [1.5- to 1.8-m] sail on adult male killer whales), these species have no diagnostic field characteristics in common. Therefore, each is discussed in detail and is placed in the text in near proximity to those species with which it is likely to be confused in the field.

[Sidenote: MINKE WHALE

_Balaenoptera acutorostrata_

p. 63]

Body to 30 feet (9.1 m), or more, long.

Body black or dark gray; area of gray shading on each side just in front of and below dorsal fin.