Whales, Dolphins, and Porpoises of the Western North Atlantic Part 15

[Ill.u.s.tration: Figure 49.--Closeup views of the heads of right whales off northeastern Florida (top left and right) and off Cape Cod, Ma.s.s.

(bottom left) clearly showing the narrow upper jaw, the bonnet, and the widely separated blowholes. In the photo on the bottom left note the extremely long baleen plates, characteristic of bowhead and right whales. (_Photos by N. Fain, courtesy of Marineland of Florida (top left and right); and W. A. Watkins (bottom left)._)]

[Ill.u.s.tration: Figure 50.--Right whales frequently throw their tail flukes high into the air and then slip nearly vertically beneath the surface. Note that the rear margin of the flukes of this species, unlike that of the humpback whale, is smooth, broad, and concaved distinctly towards a deep fluke notch. (_Photos from the northern North Atlantic by K. C. Balcomb (a-g) and off northeastern Florida by N. Fain, courtesy of Marineland of Florida (h)._)]

[Ill.u.s.tration: Figure 51.--A stranded right whale at Narragensett Bay, R.I. Note the narrow, highly arched lower jaw; the extremely long, narrow baleen plates, reaching lengths of 6.5 feet (2.0 m), or more; and the bonnet (the protuberance near the tip of the upper jaw). (_Photo from U.S. National Museum, courtesy of J. G. Mead._)]

[Ill.u.s.tration: Figure 52.--A ventral view of a harpooned female right whale at Newfoundland. Note that this species, like the bowhead, lacks the series of ventral grooves which characterize all other baleen whales of the western North Atlantic. Note also the absence of the vest of white on the chin, a feature which is characteristic of the bowhead whale. Some right whales, however, do have extensive regions of white on the ventral surface, including the chin. (_Photo from U.S. National Museum, courtesy of J. G. Mead._)]

SPERM WHALE (T)

_Physeter catodon_ Linnaeus 1758

Other Common Names

Cachalot, Sea Wap (St. Vincent).

Description

Male sperm whales have been reported to reach a length of 69 feet (20.9 m), though today individuals larger than 50 feet (15.2 m) are rare.

Females are much smaller, rarely exceeding 38 feet (11.6 m).

A sperm whale is among the easiest of whales to identify at sea even when comparatively little of the animal is visible. It has a huge head, which comprises from a fourth to a third of the animal's total length.

(The proportion is considerably higher for males than for females.) The blunted "squarish" snout, which may project up to 5 feet (1.5 m) beyond the tip of the lower jaw, houses a large reservoir containing a high-quality oil called spermaceti.

The single blowhole is located well to the left of the midline and far forward on the head. As a consequence the small bushy blow, usually less than 8 feet (2.4 m), emerges forward at a sharp angle from the head and towards the left. Under good wind conditions this feature alone may permit positive identification of sperm whales even at considerable distances.

Sperm whales have a distinct dorsal hump, usually rounded in its appearance about two-thirds of the way back from the tip of the snout.

Immediately behind the hump is a series of knuckles or crenulations along the midline. This hump and the crenulations are clearly visible when the animals arch the tail before beginning a dive. There is a ventral keel, which may also be visible as animals "sound" (dive). The flukes of sperm whales are broad and triangular in shape, are not concaved, but are deeply notched on the rear margin.

Sperm whales usually are dark brownish gray in color. The body has a "corrugated" or "shriveled" appearance. The belly and the front of the head may be grayish to off-white. The skin around the mouth, particularly near the corners, is white. The undersides of the flukes and flippers vary in color through numerous shades of browns and brownish grays.

Natural History Notes

Sperm whales may dive to depths in excess of 3,270 feet (996.7 m) for periods of an hour or more. As do most whales upon surfacing from a deep dive, sperm whales emit a single explosive blow and then, depending on the length of the dive, may remain on the surface for over 10 min and blow more than 50 times before beginning the next dive. Shorter periods on the surface and fewer blows are more common. Females may dive and remain on the surface for shorter periods of time than males. When beginning a deep dive, sperm whales throw their broad triangular flukes, dark on the undersides, high into the air.

Sperm whales may be found singly or in groups of up to 35 or 40 individuals. Older males are usually solitary except during the breeding season. During the remainder of the year large groups may be bachelor bulls (s.e.xually inactive males) or nursery schools containing females and juveniles of both s.e.xes. Sperm whales are seldom found in less than 600 feet (182.9 m) of water.

Sperm whales feed primarily on squid but may occasionally also take octopuses and a variety of fishes.

May Be Confused With

Because of their distinctive head shape and blow, sperm whales are unlikely to be confused with any other species when they can be closely examined. If only the back and tail flukes are seen, however, sperm whales may somewhat resemble humpback whales. Both species arch the back when beginning a dive, raising the fin or hump, and both throw the tail flukes. The most distinctive differences between the two species are tabularized on p. 40.

At sea the head of a sperm whale may also somewhat resemble that of an adult male northern bottlenosed whale, but this latter species is lighter brown in color, has a distinct beak and a prominent dorsal fin, and is rarely found south of lat. 42N. In addition, the blowhole of the northern bottlenosed whale is located well back on the head and not--as in the sperm whale--on the front.

Distribution

Sperm whales are widely distributed in oceanic areas of the western North Atlantic. They may be encountered from Venezuela north at least as far as the Davis Straits, though they apparently avoid the polar ice fields. Distribution and migrations vary between males and females.

Males range farther to the north, while females and immature males remain between lat. 30 and 50N. Both groups s.h.i.+ft northward during spring and summer and return to southern portions of their range in the fall. Adult males arrive off the New England coast in August. Those reaching the Newfoundland and Labrador coasts arrive from the deep sea, perhaps following the slope contours, in August and September. Males are abundant as far north as southeast Greenland and Iceland in summer. Some animals remain as late as November, but the majority migrate south to temperate or tropical waters in the early fall.

Historically the primary grounds in the western North Atlantic were those in all the following areas: the Grand Banks just southeast of the southern Grand Banks from lat. 30 to 40N and long. 35 to 55W, off the Carolinas, around the Bahamas, around many of the West Indies, and in the southwestern Caribbean.

Stranded Specimens

Stranded sperm whales should be easy to identify. The very narrow underslung jaw contains from 18 to 25 functional teeth, which fit into sockets in the upper jaw. The huge, distinctly box-shaped head and the position of the single blowhole to the left front of the head are unmistakable clues.

[Ill.u.s.tration: Figure 53.--An aerial view of 21 sperm whales, including two young calves and several large males, off j.a.pan. Even from an aircraft, the position of the blowhole and the body shape clearly mark these animals as sperm whales. (_Photos by Suisan Koku Company, courtesy of T. Kasuya._)]

[Ill.u.s.tration: Figure 54.--A side view of a sperm whale in the West Indies, showing the distinctive blow. Note that the spout projects obliquely forward from the blowhole, which is displaced to the left front of the head. (_Photo by H. E. Winn._)]

[Ill.u.s.tration: Figure 55.--Note the distinctive body shape and the position of the blowhole of these swimming sperm whales, and, in the animal on the left, the broad tail flukes. (_Photos from the North Atlantic by S. Green (left) and from the North Pacific by S. Ohsumi (right)._)]

[Ill.u.s.tration: Figure 56.--A sperm whale mother and calf off Baja California, showing the distinct dorsal hump and the extremely long head. In the bottom photo, from the West Indies, note the dorsal hump and the crenulations of b.u.mps which follow it. Both the hump and the crenulations may be visible as the animal arches its tail to begin a deep dive. Note also the wrinkled appearance of the body. (_Photo by K.

C. Balcomb (top) and H. E. Winn (bottom)._)]

[Ill.u.s.tration: Figure 57.--Sperm whales often show their broad tail flukes as they begin long dives, which may last over an hour and take them to depths of several thousand feet or more. Note the smooth rear margin and the nearly triangular shape of the flukes. (_Photo from off Baja California by K. C. Balcomb._)]

[Ill.u.s.tration: Figure 58.--A stranded infant male sperm whale at Melbourne Beach, Fla. (top) and a male adult sperm whale on the deck of a whaling s.h.i.+p in the Pacific (bottom). Note the bulging forehead, the narrow, underslung lower jaw, the white coloration around the mouth, particularly at the corners, and the wrinkled appearance of the body. In the bottom photo note also the whitish region on the belly. (_Photos by P. Winfield (top) and j.a.panese Whales Research Inst.i.tute, courtesy of H.

Omura (bottom)._)]

[Ill.u.s.tration: Figure 59.--The narrow lower jaw of a sperm whale contains from 18 to 25 large functional teeth, which fit neatly into sockets in the upper jaw. Occasionally, the upper jaw also contains some teeth. (_Photo from the North Pacific by j.a.panese Whales Research Inst.i.tute, courtesy of H. Omura._)]

[Ill.u.s.tration: Figure 60.--The throat and lower jaw of a sperm whale on the deck of an eastern Canadian whaling station, showing the numerous short throat grooves, which are most clearly evident on adult animals.

(_Photo by J. G. Mead._)]

[Ill.u.s.tration: Figure 61.--Detail of the broad, paddle-shaped flipper of a sperm whale from the North Pacific. (_Photo from j.a.panese Whales Research Inst.i.tute, courtesy of H. Omura._)]

Medium-sized Whales With a Dorsal Fin

MINKE WHALE (B)

_Balaenoptera acutorostrata_ Lacepede 1804