Whales, Dolphins, and Porpoises of the Western North Atlantic Part 23

Watkins._)]

[Ill.u.s.tration: Figure 98.--Atlantic pilot whales frequently "lob tail"

(raise the tail flukes above the surface and slap them against the water) (top) and pitchpole or spy-hop (hang vertically in the water with the head up and the tail down) (bottom). (_Photos from the North Atlantic by H. E. Winn._)]

[Ill.u.s.tration: Figure 99.--North Atlantic pilot whales on the deck of a whaling station in Newfoundland. The anchor-shaped patch on the chin and the gray color of the belly are apparently more vivid and extensive in this species than in the short-finned pilot whales. Further, the flipper is longer, measuring one-fifth of the body length, or more, in adult animals. The flippers of short-finned pilot whales (see Fig. 102) measure one-sixth of the body length or less. (_Photo by J. G. Mead._)]

SHORT-FINNED PILOT WHALE (T)

_Globicephala macrorhynchus_ Gray 1846

Other Common Names

Blackfish (see also p. 84, 91, and 94).

Description

Male short-finned pilot whales of the western North Atlantic reach lengths of at least 17.5 feet (5.3 m). Females are reportedly slightly smaller than males (recorded only to 15.5 feet [4.7 m]).

The head, somewhat like that of the Atlantic pilot whales (p. 91), is thick and bulbous, a characteristic which reaches its extreme in the development of a flattened or squarish appearance to the front of the head in mature males (see Fig. 101). In very old males the melon may overhang the mouth up to several inches. The flippers are shorter than those of the other pilot whale species of the western North Atlantic (thus the common name short-finned pilot whale), reaching only one-sixth of the body length or less. The tail is dorsoventrally thickened just in front of the flukes.

The dorsal fin, like that of the Atlantic pilot whale, is one of the species' most distinctive characteristics. It is low in profile, has a long base, and is set far forward on the animal's back.

Short-finned pilot whales are all black on the back sides and most of the belly with an anchor-shaped patch of gray on the chin and a gray area of varying extent and intensity on the belly. These areas are less vivid and extensive than those on Atlantic pilot whales. Younger animals are lighter, often medium gray.

Natural History Notes

Short-finned pilot whales are known to occur in groups of 60 animals or more, though smaller groups are more common. They have been reported pitchpoling (spy-hopping), lobtailing, and--rarely--breaching.

Short-finned pilot whales feed on squid and fish.

May Be Confused With

In the tropical portion of their range, short-finned pilot whales may be confused with pygmy killer whales (p. 138) and many-toothed blackfish (p. 142). They may be distinguished from both species primarily by their distinctive dorsal fin and the bulbous-to-squarish head. Both pygmy killer whales and many-toothed blackfish have dorsal fins, which are more falcate, slender, and pointed on the tip, and have longer, slenderer heads.

Throughout their range short-finned pilot whales may be confused with false killer whales. The two species may be distinguished by the same differences which distinguish Atlantic pilot whales from false killer whales (p. 91).

In the extreme northern portion of their range, short-finned pilot whales may be confused with Atlantic pilot whales. The two species may be distinguished by differences itemized on p. 93.

Distribution

Though short-finned pilot whales are known from Delaware Bay, their normal range appears to extend from Bermuda and Cape Hatteras (Virginia in summer) south to the Venezuelan coast. They have been reported for the Gulf of Mexico, the Caribbean, and the islands of the West Indies.

Stranded Specimens

Stranded short-finned pilot whales may be confused with any of the species itemized under living animals. They may be identified as pilot whales primarily by the robust body and bulbous head, often squarish in adult animals, and the broad-based, falcate dorsal fin located well forward on the animal's back. Accurate determination of the pilot whale species involved may require museum preparation of the skull and detailed examination of its characteristics. Preliminary identification may be made, however, on the basis of the following:

ATLANTIC PILOT WHALE SHORT-FINNED PILOT WHALE

DISTRIBUTION

Primarily North Carolina Primarily North Carolina north. south.

FLIPPERS

To one-fifth body length, To less than one-sixth body or more. length.

TEETH 8-11 per row. 7-9 per row.

[Ill.u.s.tration: Figure 100.--Short-finned pilot whales stranded in northeastern Florida, shown here swimming in the lagoon at Marineland of Florida. This species, like their northern cousins, the Atlantic pilot whales, have a highly distinctive dorsal fin and a bulbous head (see Figs. 97, 99). In these photos note the variation in the shape of the head. Those of females and immature males are more rounded. Those of adult males are far more blunted. (_Photo courtesy of Marineland of Florida._)]

[Ill.u.s.tration: Figure 101.--Short-finned pilot whales have from 7 to 10 teeth in each side of each jaw. The bulbous forehead of the species is far less p.r.o.nounced in females and immature males (left). The head of mature males is extremely "squarish" and may overhang the lower jaw by several inches (right). (_Photos from Aquatarium (left) and southeastern Florida by D. K. Caldwell (right)._)]

[Ill.u.s.tration: Figure 102.--The flippers of short-finned pilot whales reach only about one-sixth of the body length, while those of the Atlantic pilot whale may be one-fifth the body length or more. Note the length of the flippers of the pilot whale in the background, relative to its overall length. (_Photo from South Carolina by J. G. Mead._)]

GRAMPUS (T)

_Grampus griseus_ (G. Cuvier 1812)

Other Common Names

Risso's dolphin, gray grampus, white-headed grampus, mottled grampus, Risso's porpoise, hard knocks (St. Vincent), white blackfish (Cape Cod).

Description

Grampus reach a maximum length of about 13 feet (4 m). The body is robust, particularly in front of the dorsal fin, and lacks a distinct beak. The head is somewhat bulbous and is marked on the front by a V-shaped crease with the point downwards, which divides the melon into two parts. The flippers are long and pointed on the tips. The dorsal fin, located at about the midpoint of the body, is tall, to 15 inches (38.1 cm) or more, and distinctly falcate. The body narrows rapidly behind the dorsal fin and the tail stock is quite narrow. The flukes are broad, concaved on the rear margin, and deeply notched.

The bodies of grampus are a uniform light gray at birth. As the animals age, their color darkens to almost black with distinctive regions of grayish white on the belly and chest. The body of older adults is cream white or silver gray, particularly on the head, with numerous scars, presumably from encounters with other grampus and perhaps with the squid, which are one of the species' major food items.

The flippers, dorsal fin, and tail flukes usually remain dark even in adults.

Natural History Notes

Grampus are found in herds of up to several hundred individuals and may be seen "porpoising" (leaping from the water) as they surface to breathe, and breaching. They sometimes ride the bow waves of a boat.