Whales, Dolphins, and Porpoises of the Western North Atlantic Part 34

[Ill.u.s.tration: Figure 151.--A rough-toothed dolphin stranded near New Smyrna Beach, Fla. This species has from 20 to 27 fairly large teeth in each side of both the upper and lower jaws. Those teeth are sometimes marked by many fine vertical wrinkles along the crown, a characteristic from which the species derives its common name. (_Photos by D. K.

Caldwell._)]

PYGMY KILLER WHALE (T)

_Feresa attenuata_ Gray 1874

Other Common Names

Slender blackfish, slender pilot whale.

Description

Pygmy killer whales reach a length of about 8-9 feet (2.4-2.7 m). They are usually relatively slender-bodied with a rounded head, an underslung jaw, and no beak.

The falcate dorsal fin, located about the center of the back, is usually between 8 and 12 inches (20.3 and 30.1 cm) tall (though it may reach 15 inches [38 cm] in some individuals), is sometimes very distinctive, and resembles that of the Atlantic bottlenosed dolphin. The flippers are slightly rounded on the tips.

The color has been described as dark gray or black on the back, often lighter on the sides, extending higher in front of the dorsal fin and with a small zone of white on the underside, often a lighter gray area on the sides, and distinctive white regions around the lips. The chin may be completely white. This white zone on the chin, described as a "goatee," is often clearly visible in swimming animals.

May Be Confused With

The pygmy killer whale resembles the false killer whale but is much smaller and can be distinguished at close range by the zones of white coloration. False killer whales are almost all black and reach a length of up to at least 18 feet (5.5 m). Pygmy killer whales are dark gray on the back, often lighter on the sides, and show a region of white on the belly which may extend so high up onto the sides that it is visible on a swimming animal. Further, they reach only 8-9 feet (2.4-2.7 m).

Pygmy killer whales may also be confused with the similarly sized and colored many-toothed blackfish. So little is known of the two species'

appearance and behavior at sea that it is doubtful that they can be successfully distinguished, though many-toothed blackfish apparently lack the white region often seen on the sides of pygmy killer whales.

Further, pygmy killer whales have rounded flippers and smoothly tapered heads, while those of the many-toothed blackfish are pointed on the tip and more sharply pointed (often described as a parrot beak).

Distribution

Pygmy killer whales are probably distributed in the tropical and subtropical waters of the western North Atlantic. They have been reported from Texas, the Atlantic coast of Florida, and St. Vincent Island, Lesser Antilles. Records of the species from the other oceans of the world suggest that its distribution is limited to tropical and subtropical waters.

Stranded Specimens

Stranded pygmy killer whales can be clearly distinguished from both the false killer whale and the many-toothed blackfish. In addition to the differences discussed above, the following are key differences between the pygmy and false killer whales:

PYGMY KILLER WHALE FALSE KILLER WHALE

TEETH

10-13 in each side of upper 8-11 per jaw per side, and lower jaws; lower teeth prominent.

smaller.

VENTRAL COLORATION

White from a.n.u.s to under tail Dark from a.n.u.s to tail stock; stock, white may extend up lighter pale gray area forward sides. between flippers.

FLIPPERS

Smoothly rounded. Characteristic hump on forward margin.

Pygmy killer whales can be distinguished from many-toothed blackfish on the basis of the second species' larger number of teeth. (Many-toothed blackfish have from 22 to 25 teeth in the upper jaw and from 21 to 24 in the lower jaw.)

[Ill.u.s.tration: Figure 152.--Pygmy killer whales at sea northwest of Hawaii (top) off the island of Oahu, Hawaii (middle), and from southeastern Florida in the tank at the Wometco Miami Seaquarium (bottom). When swimming rapidly, pygmy killer whales may closely resemble the much larger false killer whales. In addition to their much smaller size, rarely exceeding 9 feet (2.7 m), however, pygmy killer whales can be distinguished by their more rounded head, the white coloration of the lips and chin, and the white zone on the belly, sometimes extending up the sides. (_Photos by S. Ohsumi (top); J.

Naughton, National Marine Fisheries Service and courtesy of E.

Shallenberger, Sea Life Park (middle); and courtesy of Wometco Miami Seaquarium (bottom)._)]

[Ill.u.s.tration]

[Ill.u.s.tration: Figure 153.--Pygmy killer whales 5 miles off Kaena Point, Oahu, Hawaii. These individuals were dark on the back with varying degrees of lighter coloration on the sides, extending high onto the sides in front of the dorsal fin. Many had a white "goatee" on the chin and lower jaw. The prominent dorsal fin is characteristic. (_Photos by E. Shallenberger, courtesy of Sea Life Park, Hawaii._)]

[Ill.u.s.tration: Figure 154.--Side and belly views of a pygmy killer whale from South Africa. Note the slight white coloration of the lips, the white region on the ventral surface (extending up onto the sides just below the dorsal fin), and the falcate sharply pointed dorsal fin. Note also the flippers, which lack the hump on the forward margin characteristic of false killer whales. (_Photos courtesy of P. B.

Best._)]

[Ill.u.s.tration: Figure 155.--Pygmy killer whales have from 8 to 11 teeth in each side of the upper jaw and from 11 to 13 in each side of the lower jaw. Many specimens reportedly have one fewer on the right than on the left side. The teeth are smaller than those of the false killer whale and far less numerous than those of the more closely sized many-toothed blackfish. Note also the white lips. (_Photo courtesy of P.

B. Best_)]

MANY-TOOTHED BLACKFISH (T)

_Peponocephala electra_ (Gray 1846)

Other Common Names

Hawaiian blackfish, melon-headed whale.

Description

Many-toothed blackfish reach lengths of at least 9 feet (2.7 m) and are similar in body shape to the larger false killer whale and the similar-sized pygmy killer whale. The body is elongated and slim with a rather slim tail stock. In general, the head is shaped like that of the false killer whale but has a sharper appearance to the snout, sometimes described as a parrot-beak. The forehead is rounded, slightly overhanging the lower jaw, and has no beak. The dorsal fin is up to 10 inches (25.4 cm). It is probably very distinctive as the animals surface to breathe. Many-toothed blackfish are black on the back and slightly lighter on the belly. The areas around the a.n.u.s and genitals and the lips are unpigmented. Many-toothed blackfish are presumably rare.

May Be Confused With

Many-toothed blackfish may be confused with either the false killer whale or the pygmy killer whale. They are considerably smaller than the false killer whale, have a slightly more pointed snout, and lack the prominent humplike forward margin on the flippers which is characteristic of the false killer whale.

They are approximately the same size as pygmy killer whales, but the white area around the genitals which extends up onto the side in pygmy killer whales may be lacking in many-toothed blackfish. This species has pointed flippers, while those of pygmy killer whales are rounded on the tips. Many-toothed blackfish also have a slightly more pointed snout.

Otherwise, the two species are virtually indistinguishable in encounters at sea.