Whales, Dolphins, and Porpoises of the Western North Atlantic Part 21

Very tall and erect in adult Shorter, slender, strongly males; tall and slightly back falcate.

curved in female.

HEAD SHAPE

Broad, rounded. Tapered, slender.

FLIPPER SHAPE

Paddle-shaped. Moderately long with characteristic hump near middle on forward margin.

LENGTH

To at least 30 feet (9.1 m). To at least 18 feet (5.5 m).

Furthermore, false killer whales are the only "blackfish" which are known to ride the bow wave of a s.h.i.+p.

Grampus have a tall dorsal fin (15 inches [38.1 cm]) which is very similar in appearance to that of adult female and juvenile killer whales. But grampus have much lighter coloration, from slate gray to nearly all white, and larger animals are covered with numerous scratches. Upon closer examination they can be further distinguished from killer whales by a crease in the front of the head dividing the melon into two distinct sections. Grampus are considerably smaller, to about 13 feet (4 m) maximum length.

Distribution

In the western North Atlantic killer whales have been reported from the polar pack ice south to Florida and St. Vincent, Lesser Antilles, and into the Gulf of Mexico at least as far as Texas, though they are far more common in the cooler waters from about New Jersey north.

Throughout their range, killer whales seem to prefer coastal areas and often enter shallow bays, estuaries, and river mouths in search of food.

Migrations of the species are probably closely tied to movements of their food supply. They annually arrive on the coast of New England with the tuna. Along the Canadian coasts, where distribution and migrations have been described in some detail, killer whales appear to move insh.o.r.e in spring and summer. Many arrive off the east coast of Newfoundland in June, the Strait of Belle Isle in June and July, and slightly later along the Labrador coast and Arctic waters. They are found around the loose ice in April, presumably feeding on harp seals, _Pagophilus groenlandicus_, and hooded seals, _Cystophora cristata_, and are frequent in the St. Lawrence estuary in spring and autumn following the movements of the white whales. The northward movements in spring also coincide with migrations of balaenopterine whales, which have also been reported among the food items. Killer whales may remain in arctic or subarctic waters until driven out by new forming ice in October and November. Though the migration has not been as thoroughly described, killer whales apparently begin s.h.i.+fting southwards in autumn.

Stranded Specimens

Stranded killer whales should be readily identifiable by the robust body, the distinctive body markings, and in larger animals the tall dorsal fin. Killer whales have from 10 to 12 large, prominent teeth on each side of the upper and lower jaws.

[Ill.u.s.tration: Figure 89.--Killer whales are often distributed very close to sh.o.r.e. In these photos from Baja California, they are shown in two characteristic behaviors--breaching (top) and "spy-hopping" or "pitchpoling" (bottom). (_Photos by S. Leatherwood._)]

[Ill.u.s.tration: Figure 88.--A small herd of killer whales off southern California (top) and details of an adult male from that herd (middle) and of females or immature males off Islas San Benito, Baja California (bottom). Adult males have a tall erect dorsal fin, which may be more than 6 feet (1.8 m) tall, while the fins of females and immature males are less than 3 feet (0.9 m) tall, distinctly falcate, and pointed on the tip. Both s.e.xes frequently have a grayish-white region, called a "saddle," behind the dorsal fin. (_Photos by T. Dohl (top and middle) and S. Leatherwood (bottom)._)]

[Ill.u.s.tration: Figure 90.--A leaping killer whale in California aquarium. Note the distinctive coloration of the species, white on the lower jaw, the belly and the a.n.u.s, and on both sides above the a.n.u.s.

Note also the distinctive white eye patch often visible on animals at sea. (_Photo by D. K. Caldwell._)]

[Ill.u.s.tration: Figure 91.--Killer whales have from 10 to 12 large prominent teeth, curved slightly backwards and inwards on each side of each jaw. (_Photos from Point Mugu, Calif. by S. Leatherwood._)]

FALSE KILLER WHALE (T)

_Pseudorca cra.s.sidens_ (Owen 1846)

Other Common Names

Mongoose (St. Vincent).

Description

False killer whales in the western North Atlantic reach a length of at least 18 feet (5.5 m). Males are slightly larger than females. Calves from 5 to 7 feet (1.5 to 2.1 m) may be seen at any time throughout the year.

The dorsal fin, located just behind the midpoint of the back, is from 7 to 16 inches (17.8 to 40.6 cm) tall, falcate, and variable to sharply pointed on the tip. The flippers are characterized by a broad hump on the front margin near the middle, a characteristic which is diagnostic for the species.

The body of the species is all black except for a blaze of gray on the belly between the flippers. This blaze varies from barely visible to light grayish white similar to but generally fainter than that of pilot whales. The body is long and slender, and the head is narrow and gently tapered from the area of the blowhole forward.

Natural History Notes

False killer whales are a social form and may occur in herds of up to at least 100 individuals. They often jump clear of the water and frequently ride the bow waves of vessels. They are the only "blackfish" which are known to do so. False killer whales feed primarily on squid and large fishes and are notorious for their habit of stealing fish from the lines of fishermen. The large prominent teeth may be visible on a swimming animal.

May Be Confused With

False killer whales may be confused with killer whales, pilot whales, or the smaller, poorly known pygmy killer whale (p. 138) and many-toothed blackfish (p. 142).

The characteristics distinguis.h.i.+ng the species from the killer whale are tabularized on p. 84; its differences from the pilot whales are summarized on p. 92.

At sea, false killer whales are distinguishable from the other two species primarily by their larger size and differences in coloration.

False killer whales are up to 18 feet (5.5 m) in length. Pygmy killer whales and many-toothed blackfish reach only 8-9 feet (2.4-2.7 m) in length. Pygmy killer whales have an extensive region of white on the belly which may extend onto the sides and both pygmy killer whales and many-toothed blackfish have a distinctive white region on the lips, usually lacking or indistinct on false killer whales.

Neither of the smaller species of blackfish has been reported to ride bow waves.

Distribution

False killer whales are widely distributed in the pelagic tropical, subtropical, and warm temperate waters of the western North Atlantic.

They have been reported from off Maryland south along the mainland coasts of North America, in the Gulf of Mexico from Cuba and the Lesser Antilles, and from the southeast Caribbean Sea. The species has been reported from Venezuela.

Stranded Specimens

Stranded false killer whales can be positively identified by: 1) the large size (to 18 feet [5.5 m]); 2) the slender body tapering rapidly to a long slender head; 3) the markedly long mouth, with from 8 to 11 large, conspicuous teeth in each side of each jaw recalling those of the killer whale, but circular and not, as in killer whales, elliptical; 4) the unusually shaped flipper bulging conspicuously on the forward margin.

For comparison with "blackfish" of similar size (the pilot whales) see p. 92 and 94.

False killer whales do not appear to occur frequently in coastal waters, sandy bays, or estuaries, though entire herds have stranded in such areas. Records from throughout the range suggest that the species has an oceanic distribution.

[Ill.u.s.tration: Figure 92.--False killer whales at sea 600 miles (968.0 km) off northeastern Florida. Note the smoothly falcate dorsal fin, pointed on the tip, and located near the midpoint of the back. Dorsal fins of this species may also be rounded on the tip but all are sharply concaved on the rear margin. (_Photo by H. E. Winn._)]

[Ill.u.s.tration: Figure 93.--False killer whales are the only "blackfish"

that routinely ride the bow waves of vessels. On this animal riding on the bow wave of a research s.h.i.+p, note the all-black coloration of the back, head, and sides and the broad "hump" near the middle of the flippers on the leading edge. (_Photo 600 miles [968 km] off northeastern Florida by H. E. Winn._)]