Whales, Dolphins, and Porpoises of the Western North Atlantic Part 25

Stranded Specimens

Stranded belugas are unlikely to be confused with any other species of cetaceans. The all-white coloration, the robust body shape with a rather small head and a distinct neck region, and the presence of 8-11 teeth in each of the upper jaws and 8-9 in each of the lower jaws permit positive identification.

[Ill.u.s.tration: Figure 108.--A group of three belugas surfacing to breathe off northwestern Alaska. The animal to the right has just begun to exhale, the middle animal is in the midst of his inhalation, and the animal on the left has completed his blow and is preparing to dive. Note the all-white coloration and, on the center animal, the small dorsal ridge just emerging from the water. Details of the dorsal ridge are clearly visible in the inset photograph. (_Photos by G. C. Ray and K. G.

Hewlett (inset)._)]

[Ill.u.s.tration: Figure 109.--Note the robust form and the small head of this swimming beluga off northwestern Alaska. (_Photo by G. C. Ray._)]

[Ill.u.s.tration: Figure 110.--Captive belugas at Vancouver public aquarium. Note the dorsal ridge, the shape of the head and body, and the unusually shaped flippers. (_Photo by K. C. Balcomb._)]

[Ill.u.s.tration: Figure 111.--Ventral view of a beluga harpooned in the northeastern Canadian Eskimo Fishery. Note the very narrow tail, just in front of the flukes, and the robust form of the species. Belugas have 8-9 teeth in each of the lower jaws, and 8-11 in each of the upper jaws.

(_Photo by P. F. Brodie._)]

NARWHAL (T)

_Monodon monoceros_ Linnaeus 1758

Other Common Names

Unicorn whale (historical name not currently in use).

Description

The narwhal, also known as the unicorn whale because of the long tusk found on adult males, is one of two medium-sized whales found in the Arctic waters of the northwestern Atlantic. They reach a maximum length of from 15 to 16 feet (4.6 to 4.9 m) excluding the tusk. Newborn calves are approximately 5 feet (1.5 m) long. Narwhals have small rounded heads and a small mouth. Like the other medium-sized whale in the same region, the beluga or white whale, the narwhal has no dorsal fin. Instead, it has a series of b.u.mps, approximately 2 inches (5.1 cm) high along the midline of the back in the half nearest the tail. The ridge created by these b.u.mps may be readily seen on a swimming animal.

The basic coloration of the species changes slightly with age. Young animals are uniformly dark bluish gray on the back but rapidly begin to develop the numerous leopardlike spots on the back and sides characteristic of adults. Those spots rarely extend onto the belly even in old animals.

Narwhals have only two teeth. In the females, these teeth rarely emerge from the gums. In males, one and sometimes both of those teeth grow out the front of the snout, spiraling in a left-hand or sinistral direction, and may reach a length of 9 feet (2.7 m). One or two tusks may also be exposed, however, in females.

Natural History Notes

The function of the tusk in male narwhals is unknown, but it was this feature of the animal that earned it the name "unicorn whale" and resulted in its extensive hunting by whalers. During their annual migrations narwhals may congregate but are commonly found in groups of 10 or fewer during the rest of the year.

Narwhals feed on a variety of organisms, including cod, rockfish, flounder, and crabs, but their diet consists primarily of squid.

Distribution

Narwhals are found in the high arctic seas of the western North Atlantic, primarily in Lancaster Sound and its fringes. It has been noted that they are found in isolated pockets within that range and are not, like the beluga, widely distributed.

Narwhals make annual migrations in response to the movement of the ice.

During the fall as the ice begins to form, the whales migrate to the south, sometimes reaching the Labrador coast. In the spring they return to the pack ice.

May Be Confused With

Narwhals are so different in coloration from the only medium-sized cetacean which shares its range and habitat--the beluga--that the two are highly unlikely to be confused. Belugas are usually all white or light slate gray in color, while narwhals are very much darker, ranging from bluish gray to brownish, and are often covered with light leopardlike spots. Furthermore, the body of the beluga is more robust.

Further, swimming narwhals frequently buck their heads up to breathe, a behavior which makes the tusk of adult males visible and permits positive identification.

Stranded Specimens

Stranded narwhals should be easily identifiable by the distinctive coloration and the unique characteristics of the teeth. In adults, one or two of the teeth may develop into the long, left-hand spiraling tusk, shown in Figures 112 and 114. Immature animals have no teeth which are emerged.

[Ill.u.s.tration: Figure 112.--In this photo of narwhals, the origin of the name "unicorn whale" is apparent. The animal at the right, an adult male, exposes his tusk as he surfaces aggressively to breathe. Even when this feature is not observed, however, the narwhals' mottled gray coloration makes them easy to distinguish from the all-white belugas, with which they share a common range. Note also the dorsal ridge on the animal to the left. (_Photo by D. Lusby, courtesy of the Sea Library._)]

[Ill.u.s.tration: Figure 113.--A juvenile narwhal in a tank at New York Aquarium. Though newborn animals are dark bluish gray on the back, fading to white on the belly, note that the mottled gray coloration characteristic of adults is well developed even in relatively young animals. The white region on the head is lanolin cream, applied to protect the animal's skin during transport. (_Photo by H. E. Winn._)]

[Ill.u.s.tration: Figure 114.--A stranded male narwhal. The long unicorn tusk is the spiral extension of one of the two teeth, though the other may be exposed above the gums in males and may even develop into a second long tusk; both teeth of females are normally buried in the gums and rarely emerge. Note the highly distinctive dorsal ridge, near the midpoint of the back. (_Photos by D. Lusby, courtesy of the Sea Library._)]

Small Whales, Dolphins, and Porpoises With a Dorsal Fin

ATLANTIC SPOTTED DOLPHIN (T)

_Stenella plagiodon_ (Cope 1866)

Other Common Names

Spotter, Gulf Stream spotted dolphin, spotted porpoise, long-snouted dolphin.[11]

[Footnote 11: See also p. 110. The common name "long-snouted dolphin"

was once widely used for this species. It is now more frequently used for _Stenella longirostris_, also known as the spinner dolphin.]

Description

Atlantic spotted dolphins reach a maximum adult length of 7.5, perhaps 8 feet (2.3 to 2.4 m). They are generally more robust in body shape than the other species of Stenella, closely resembling Atlantic bottlenosed dolphins in that regard, though the Atlantic spotted dolphins tend to be more slender.

The dorsal fin is distinctly back-curved and pointed on the tip, also closely resembling that of the Atlantic bottlenosed dolphin.

As the common name suggests, the Atlantic spotted dolphins are marked dorsally with numerous grayish-white spots on a darker background and ventrally with dark spots on a lighter background, though the extent of the spotting and the additional details of coloration change with age.

Immature animals lack spots completely. They are dark gray or purplish gray on the back, becoming lighter gray on the sides and white on the belly. The cape along the back is distinctly separated from the lighter gray coloration of the sides. The flippers and the trailing edge of the flukes are darker than the rest of the body.