Whales, Dolphins, and Porpoises of the Western North Atlantic Part 22

[Ill.u.s.tration: Figure 94.--A false killer whale stranded in northeastern Florida. Note the narrow tapering head, overhanging the lower jaw by several inches, the position and shape of the dorsal fin and the distinctive "hump" on the leading margin of the flippers. (_Photo by W.

A. Huck, courtesy of Marineland of Florida._)]

[Ill.u.s.tration: Figure 95.--Entire herds of false killer whales sometimes strand themselves. In this dorsal view of an animal stranded in southeastern Florida, note the extremely distinctive "hump" on the forward margin of the flippers and the narrow head, tapering towards the tip of the snout. (_Photo by J. Krol._)]

[Ill.u.s.tration: Figure 96.--False killer whales have from 8 to 11 large, conspicuous teeth in each side of each jaw. These teeth are often visible in swimming animals, particularly when they are engaged in their obnoxious habit of stealing fish from the lines of fishermen. The teeth are so distinctive that they can also be used to identify even a badly decomposed stranded specimen. (_Photo, courtesy of Sea Life Park, Hawaii._)]

ATLANTIC PILOT WHALE (T)

_Globicephala melaena_ (Traill 1809)

Other Common Names

Northern pilot whale, long-finned pilot whale, pothead, blackfish, calling whale, caa'ing whale.

Description

Male Atlantic pilot whales reach an average length of at least 20 feet (6.2 m). Females are slightly smaller, probably not exceeding 18 feet (5.5 m). Young are 5-7 feet (1.5-2.1 m) at birth.

The head is thick and bulbous, a characteristic which reaches an extreme in the development of the head of adult males (prompting the common name "pothead"). The flippers are long (to one-fifth of the body length, or more) and sickle-shaped. The tail is dorsally thickened just in front of the flukes.

The dorsal fin of this species is one of its most distinctive characteristics. It is low in profile, has a long base, is set far forward on the animal's back, and is falcate to "flaglike" in appearance. The dorsal fin of adult males reportedly has a thicker leading edge and a rounder form than that of the female.

Atlantic pilot whales are black on the back and sides (prompting the common name "blackfish") but have an anchor-shaped patch of grayish white on the chin and a gray area on the belly, both of which are variable in extent and intensity. Some larger animals have a gray saddle behind the dorsal fin, though this zone of color is found more frequently in short-finned pilot whales. Young animals are often a lighter medium gray.

Natural History Notes

Atlantic pilot whales may occur in herds of 200 animals or more, though herds of 50 or fewer (4-6) are more common. They are sometimes found in a.s.sociation with Atlantic white-sided dolphins.

Pilot whales are sometimes found hanging vertically in the water with the head and part of the back out of the water in what has been called "spy-hopping" or "pitchpoling." Individuals frequently lobtail. Pilot whales infrequently breach, a behavior which is usually confined to younger animals. They do not ride bow waves.

Atlantic pilot whales feed primarily on squid but also take cod and other fishes. A Pacific pilot whale, a closely related species, was found by radio telemetric studies to be capable of diving to 2,000 feet (609.6 m).

Atlantic pilot whales were formerly the object of an active sh.o.r.e fishery off Newfoundland (1950-1971). In addition, entire herds and, less frequently, individuals are sometimes stranded.

May Be Confused With

Atlantic pilot whales are most likely to be confused with false killer whales, with which they share the waters from off Virginia to those off Maryland. The two species may be distinguished by the following characteristics:

ATLANTIC PILOT WHALE FALSE KILLER WHALE

SHAPE OF HEAD

Thick and often squarish in Slender, gently tapering larger animals. mouth long.

SHAPE OF BODY

Robust. Long and slender.

DORSAL FIN

Broad-based and falcate. Slender, tall, falcate, and pointed on tip.

COLORATION

Black with gray saddle Mostly black with gray blaze sometimes evident behind of variable extent and dorsal fin and gray region intensity on belly between on chin and belly. flippers.

BEHAVIOR

Will not ride bow waves; May ride bow waves, often seldom breaches. "porpoises" and breaches.

RANGE

Temperate waters from at Temperate seas from at least least North Carolina north. Maryland south.

In the extreme southern portion of their range, Atlantic pilot whales may be confused with short-finned pilot whales with which they have only a limited seasonal common range. Characters distinguis.h.i.+ng these species are subtle and may not be adequate to permit them to be distinguished at sea. For purposes of this guide it is generally that pilot whales living north of lat. 38N (Virginia coast) are Atlantic pilot whales and those living south of lat. 38N are short-finned pilot whales.

Distribution

Atlantic pilot whales, the northernmost of the two pilot whales species, are found in winter from the Grand Banks south as far as North Carolina and in summer from Iceland and Greenland south to the New Jersey coast.

Winter concentrations of pilot whales may be found off the Newfoundland coast and near Cape Cod, Ma.s.s. Atlantic pilot whales are distributed both in coastal waters and in deep waters off the continental shelf.

Stranded Specimens

As discussed above, individuals and groups of pilot whales frequently strand themselves for still incompletely understood reasons. They may be identified as pilot whales primarily by: 1) the robust body and bulbous head, which is often squarish in adult animals, and 2) the broad-based, falcate dorsal fin located far forward on the back. Accurate determination of the pilot whale species involved in the stranding may require museum preparation of the skull and detailed examination of its characteristics. Preliminary identification may be made, however, based on the following:

ATLANTIC PILOT WHALE SHORT-FINNED PILOT WHALE

FLIPPER LENGTH

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

NORMAL RANGE

From North Carolina north. From North Carolina south.

TEETH

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

[Ill.u.s.tration: Figure 97.--A herd of Atlantic pilot whales off Ma.s.sachusetts. The most distinguis.h.i.+ng field characteristic of this species, and of their southern cousins, the short-finned pilot whales, is the highly distinctive dorsal fin, extremely long based, low in profile, and set well forward on the animals' backs. (_Photo by W. A.