Part 7

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 documented. 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 shore 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 latitude 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 shore 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 offshore 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.

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 pronounced 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 quantities 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.

Sperm whales (p. 57) have a squarish head that may somewhat resemble that of an adult male northern bottlenosed whale. However, there are numerous characteristics which will permit these species to be distinguished even from a distance:

NORTHERN BOTTLENOSED WHALE SPERM WHALE

BLOW

Low and bushy; projects Low and bushy, projects upward from indentation on obliquely forward from left top of head. side of head; usually less than 8 feet (2.4 m).

COLORATION

Lighter brown; adults splotched Brownish gray; body appears with grayish white; wrinkled. body smooth.

FLUKES

Rarely notched; seldom raised Notched; raised on long dive. on long dive.

HEAD

Tapering in younger animals; Squarish, long, all black; bulbous in adults; beakless. white in older animals; beaked.

A further aid to distinguishing northern bottlenosed and sperm whales at sea is the fact that the sperm whales that are found in areas where northern bottlenosed whales are encountered are usually older, larger males from 40 to 60 feet (12.2 to 18.3 m) long. Northern bottlenosed whales do not exceed 32 feet (9.8 m).

Northern bottlenosed whales may also be confused with the poorly known North Sea beaked whale (p. 82). When they can be examined at close range, however, northern bottlenosed whales should be distinguishable on the basis of the distinctly bulbous forehead.

Distribution

In the western North Atlantic, northern bottlenosed whales are restricted to Arctic and north temperate waters, where they most commonly occur in offshore areas. They have been reported from Davis Straits and the entrance to Hudson Strait, the Gully southeast of Sable Island, and as far south as Narragansett Bay, R.I.

In the spring and summer they concentrate near the northern limits of their range, occasionally visiting deep channels of the Gulf of St. Lawrence and eastern Newfoundland in summer. During these seasons they may extend to the edge of the pack ice.

In the fall and winter the bulk of the population migrates southward. Many probably winter in the Labrador Sea while others move farther southward and farther offshore.

Stranded Specimens

Like the beaked whales discussed on p. 70 through 83, the northern bottlenosed whales have no notch in the tail flukes, have two throat grooves forming a V-shape on the chin, and have only two teeth in the lower jaw, with those teeth emerged from the gums only in adult males. These teeth may have sometimes fallen out of older males, but the tooth sockets should still be visible in the gums.

NOTE: Some specimens--both male and female--will be found to have a series of vestigial teeth the size of toothpicks in the upper and/or lower jaws. Similar vestigial teeth, 5-40 in number, sometimes occur in goosebeaked whales (p. 70). Further when they are prepared for museum collections, the lower jaws of adult northern bottlenosed whales may be found to contain a second pair of teeth just behind the first.

Northern bottlenosed whales may be distinguished from the remainder of the beaked whale family, however, by the extremely robust body, by the bulbous forehead, which is more extensively developed in larger animals, particularly males, and by the pronounced dolphinlike beak.

GOOSEBEAKED WHALE (T)

_Ziphius cavirostris_ G. Cuvier 1823

Other Common Names

Ziphius, Cuvier's beaked whale, grampus (St. Vincent) (see also p. 96).

Description

Goosebeaked whales reach a length of 23 feet (7 m). Females are slightly larger than males of the same age. Calves are probably less than about 6 feet (1.8 m) at birth. The head is small relative to the body length and, when viewed laterally, is slightly concaved or scooped on the upper margin. The cleft of the mouth is small, smaller than in any other species of beaked whales. The beak is indistinct in larger individuals. There is a distinct indentation on the back behind the head. Two teeth are found at the tip of the lower jaw of adult males only.

The dorsal fin is relatively tall and distinct, to at least 15 inches (38.1 cm), smoothly falcate, and located well behind the midpoint of the back. The blowhole is located far forward on the top of the head. The blow, which may project slightly forward and slightly off to the left, is usually low and inconspicuous. Though the first blow after a long dive may be more distinct, even it is rarely visible even under good wind conditions for more than a few hundred yards.

Descriptions of the color pattern vary. Individuals may be dark rust brown, slate gray, or fawn colored on the back and generally lighter on the belly. Some appear dark in both regions, still others--particularly youngsters--appear lighter gray or tan on the belly. The body is frequently covered with white or cream-colored blotches (particularly on the belly). The tail flukes are dark on the bottom. The head is frequently paler in color. Old males have a distinct white head and are frequently extensively scarred.

Natural History Notes

Goosebeaked whales frequently occur in groups of from 10 to as many as 25 individuals. They have been reported to jump clear of the water. They are presumably deep divers and are known to stay down for more than 30 min. When they begin a deep dive, they often raise their tail flukes above the surface and dive nearly vertically. Goosebeaked whales feed primarily on squid.

May Be Confused With

So little is known of the external appearance and behavior of the living beaked whales at sea that all the species may easily be confused.

Goosebeaked whales are larger than all other beaked whale species with the exception of the northern bottlenosed whale. Upon close examination they may be distinguished from the northern bottlenosed whale by the lighter coloration of the head, reaching an extreme in the white head of adult males. (See p. 67 and Fig. 75.)

Distribution

As with other species of beaked whales seldom encountered or at least seldom positively identified at sea, the distribution of goosebeaked whales is poorly known and must be constructed from records of stranded specimens. Such records, often involving sick individuals that may have washed ashore from considerable distances, may give an inaccurate picture of normal ranges.

In general, stranding reports suggest that goosebeaked whales are sparsely but widely distributed in nonpolar latitudes. They appear to be primarily tropical in distribution, though they venture into temperate areas in summer. They have been reported from Massachusetts and Rhode Island south to Florida and thence to the islands of the West Indies. They are frequently stranded along the Florida coast and are not an uncommon species in the extant whale fishery of the Antillean Islands. The fact that goosebeaked whales strand more frequently than other beaked whales may reflect either a greater abundance or a greater tendency to approach close to shore.

They are probably primarily an offshore species.

Stranded Specimens

To be positively identified, stranded goosebeaked whales in an advanced state of decomposition may require museum preparation and examination of the skull and teeth. Fresh specimens may be tentatively identified by the characters illustrated in the figures.

OTHER BEAKED WHALES (T)

_Mesoplodon_ spp.

Other Common Names

Grampus (St. Vincent) (see also p. 96).

Description

In addition to the northern bottlenosed whale (p. 67) and the goosebeaked whale (p. 70), four other species of beaked whales have been reported from the western North Atlantic. All four species are known primarily from stranded specimens and have been rarely encountered at sea. Therefore statements of range are usually limited to inferences from locations of strandings, and information on appearance and habits of the species in the wild is almost totally lacking.

The infrequent encounters with beaked whales at sea may result from such factors as 1) a low inconspicuous blow, 2) avoidance of ships, and/or 3) distribution in small groups in offshore areas well outside the normal boating lanes.

The following descriptions will aid primarily in identifying stranded specimens. Though subtle differences in ranges, color patterns, and dorsal fin shapes and positions may be helpful in narrowing the choices of living animals, the species will continue to be extremely difficult to distinguish from one another in the brief encounters typical at sea until additional data are collected.

The beaked whales have the following characteristics in common: 1) two small creases forming a V-shape on the throat, 2) the absence of a conspicuous notch on the rear margin of the tail flukes (some specimens have a slight indentation), and 3) the absence of functional teeth in all except adult males. Adult males have a single pair of teeth in the lower jaw, the position and description of which help to identify the species. The teeth of females are not functional and only rarely emerge from the gums. Therefore, if a stranded animal is an adult male, its species can be determined by the position and description of the teeth. For example, in _Mesoplodon mirus_, the teeth are located near the tip of the lower jaw; in _M. europaeus_, they are located about a third of the way from the tip of the snout to the corner of the mouth; in _M. bidens_, they are nearly half way from the tip of the snout to corner of the mouth; and in M. densirostris, they are located in large prominences near the back of the mouth.

If the animal is a female or an immature male, however, museum preparation and examination might be required before the species can be positively determined. The following four sections summarize characters of western North Atlantic beaked whales.