Whales, Dolphins, and Porpoises of the Western North Atlantic Part 16

Other Common Names

Little piked whale, lesser rorqual, little firmer, sharp-headed finner, grampus (Newfoundland), gibord (Quebec).

Description

Minke whales are the smallest baleen whale species in the northern hemisphere, reaching maximum lengths of just over 30 feet (9.1 m). One of the most distinctive features of this species is an extremely narrow, pointed, distinctly triangular rostrum with a single head ridge, similar to but much sharper than that of the fin whale (hence the common name "sharp-headed finner"). Minke whales have a tall, falcate dorsal fin located in the latter third of the back, in about the same position as that of the sei whale, which often becomes visible simultaneously with the low, usually inconspicuous blow.

Minke whales are black to dark gray on the back and white on the belly and on the underside of the flippers. Portions of the underside of the flukes may be steel bluish gray. They have a diagonal band of white on each flipper, the extent and orientation of which varies individually.

Like the fin whale, minke whales (at least from the Pacific) sometimes have a chevron on the back behind the head and often have two regions of lightish-gray coloration on each side--one just above and behind the flippers; another just in front of and below the dorsal fin. These patches may be quite conspicuous on some animals, indetectable on others. These markings may also be present on Atlantic specimens, though they have not yet been doc.u.mented. The baleen, which may be visible from close range when the animal is feeding, is mostly yellowish white with fine white bristles. The posterior plates (up to half) may be brown to black.

Natural History Notes

Minke whales are frequently found as single animals, pairs, or trios, though they may congregate in areas of food concentration in the northern seas during the spring and summer. They are more likely to be seen up close than their larger cousins--the blue, fin, and sei whales--because they often closely approach boats, particularly stationary boats, as if curious about them.

Minke whales may also approach very close to sh.o.r.e and often enter bays, inlets, and estuaries.

Like fin whales, they often arch the tail stock high into the air when beginning a long dive. However, they do not raise the flukes above the surface when beginning a dive.

Minke whales feed primarily on small shoal fish (herring, cod, pollack, and capelin).

Minkes sometimes breach, leaping completely clear of the water and entering smoothly, head first, or with a substantial splash like humpback whales.

May Be Confused With

When they are seen at relatively close range, minke whales can be readily distinguished from the other rorquals that have relatively tall, falcate dorsal fins (fin, sei, and Bryde's whales) by their considerably smaller size and by their distinctive white band on each flipper.

At a distance, however, positive identification may be difficult. Minke whales have a small, low, inconspicuous blow. Like sei whales, they frequently expose the dorsal fin simultaneously with the blow, but minke whales hump the tail stock much higher when beginning a long dive--more like fin whales.

From a distance, minke whales might also be mistaken for northern bottlenosed whales (or any of several other beaked whales with a similar dorsal fin). They can be distinguished by the differences in head shape, body color and markings, and behavior, detailed on p. 67.

Distribution

Minke whales are distributed in the polar, temperate, and tropical waters of the western North Atlantic. They are found from the pack ice south to at least Anguilla, Lesser Antilles, and the eastern Gulf of Mexico, though they appear to be most abundant in temperate waters north of the lat.i.tude of New York and are infrequently reported from tropical waters. At least some of the population migrates to the northern portions of their range in spring and back south in autumn. They often approach close to sh.o.r.e and enter river mouths, inlets, and estuaries.

Minke whales arrive along the Canadian coast in May or June. Some migrate as far north as Hudson Strait, where they remain until the freeze in October, November, or December. By December the majority of the population has begun to move to the south, although some animals remain behind so long as to become entrapped in the ice and die. Spring and summer concentrations along the Canadian coast correspond to concentrations of capelin, cod, and herring. Southern concentrations, also corresponding with concentrations of herring, extend farther offsh.o.r.e at least to the edges of the Grand Bank. Minke whales also summer off the south coast of western Greenland, which they probably reach from waters southwest of Iceland. Minke whales also occur in deep pelagic waters.

Stranded Specimens

Stranded minke whales can be most readily identified by: 1) their small size (to just over 30 feet [9.1 m]); 2) the transverse white bands on the flippers; 3) the yellowish-white baleen plates (up to half the posteriormost plates may be brown or black), 300-325 per side in number and having fine white bristles (the plates are up to 4.75 inches [12 cm]

wide at the base and up to 8 inches [20.3 cm] long); and 4) by the 50-70 thin ventral grooves, ending well before the navel, often just even with the flippers.

[Ill.u.s.tration: Figure 62.--The minke whale, at a maximum length of just over 30 feet (9.1 m), the smallest baleen whale species of the western North Atlantic, is distributed in polar, temperate, and tropical waters.

These animals usually have a low, inconspicuous blow and are sometimes curious enough about boats that they will alter their course to investigate them. Note the two areas of light gray on the sides of the body, characteristic of at least Pacific minke whales. (_Photo from off British Columbia, courtesy of_ Nanaimo Free Press.)]

[Ill.u.s.tration: Figure 63.--Three views of minke whales at sea. In all note the transverse band of white on the flippers and the sharply pointed head. Note the gray chevron visible on the back (top), the absence of a conspicuous blow and the appearance of the prominent dorsal fin on the surface while the blowholes are still exposed (middle), and the distinctive regions of light gray on the sides (bottom). (_Photos from off San Diego, Calif. by G. E. Lingle (top); from the northern West Indies by H. E. Winn (middle); and from the western Pacific by j.a.panese Whales Research Inst.i.tute, courtesy of H. Omura (bottom)._)]

[Ill.u.s.tration: Figure 64.--Minke whales are also known as sharp-headed finners. On this animal from the North Pacific, note the sharply pointed head and the single central head ridge. (_Photo by j.a.panese Whales Research Inst.i.tute, courtesy of H. Omura._)]

[Ill.u.s.tration: Figure 65.--A minke whale stranded at Santa Barbara, Calif. Note the dark back, the white-banded flipper, and the 60-70 fine ventral grooves extending to just behind the flippers. The short, white baleen plates are visible in the open mouth. (_Photo by S. Anderson._)]

[Ill.u.s.tration: Figure 66.--Minke whales have from 300 to 325 short, yellowish-white baleen plates (up to half the anteriormost plates may be brown or black) with fine white bristles on each upper jaw. (_Photo from Santa Barbara, Calif. by S. Anderson._)]

NORTHERN BOTTLENOSED WHALE (T)

_Hyperoodon ampullatus_ (Forster 1770)

Other Common Names

None known.

Description

Northern bottlenosed whales reach a length of 32 feet (9.8 m) and are robust in form. They are characterized by a bulbous forehead, which is more p.r.o.nounced on larger animals and most distinctive in adult males, and by the dolphinlike beak displayed in animals of all sizes and ages, which is sometimes visible as the animals surface steeply to breathe.

The blowhole is located in an indented area behind the bulbous forehead, and the blow emanating from it projects upward or slightly forward to a height of up to 6 feet (1.8 m), is bushy and is visible from a considerable distance under low wind conditions. The dorsal fin, located two-thirds of the way back on the back, reaches at least 12 inches (30.5 cm) in height and is distinctly falcate. The dorsal fin may be visible from a distance of several hundred meters.

Northern bottlenosed whales are usually brownish in color, though the markings change with age. Smaller animals are a uniform chocolate brown.

Larger animals retain the chocolate brown color on the back but are often lighter on the sides and the belly and often have irregular patches or blotches of grayish-white coloration on the back and sides.

Extremely large animals, presumably older males, often have a white head. The flippers and the undersides of the flukes are uniformly brown in color.

Natural History Notes

Northern bottlenosed whales often form tightly packed groups of up to 10 or more animals. This species holds the anecdotal record for the longest dives, having been reported by early whalers to remain submerged over 2 h. They are probably deep divers, feeding primarily on squid (though they may take fishes as well), and they rarely go in water shallower than 100 fathoms (183 m).

After a long dive, northern bottlenosed whales will sometimes remain on the surface for 10 min or more, blowing at regular intervals before making another dive. After the last blow of a series or when the animals are startled by a boat, they may show the tail flukes as they begin to dive. The flukes are not notched on the rear margin.

Northern bottlenosed whales have been observed to show curiosity about boats, coming to them from a considerable distance. They have also been observed to "lobtail," raising the tail flukes above the water and slapping them against the surface, and to jump clear of the water.

In the late 19th century, after stocks of bowhead whales were severely reduced by overwhaling, northern bottlenosed whales became a prime target of arctic whalers. They were sought because in addition to whale oil produced from the body blubber, the forehead of the species yielded quant.i.ties of spermaceti like that obtained from sperm whales.

May Be Confused With

Northern bottlenosed whales have a northerly and deep-water distribution. Within their range, they may be confused at a distance with minke whales, with sperm whales, or perhaps with North Sea beaked whales.

Minke whales (p. 63) have a falcate dorsal fin located in approximately the same position as that of the northern bottlenosed whale. However, minke whales have a flathead in front of their two blow holes and are black to dark gray on the back.