SPERM WHALE (T) 



PhysetercatodonLinnaeus 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 (sexually inactive males) 

 or nursery schools containing females and juveniles of both 

 sexes. Sperm whales are seldom found in less than 600 feet 

 (182.9 m) of water. 



Sperm whales feed primarily on squid but may occasion- 

 ally 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. 42°N. 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 Alantic. 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 50°N. Both groups shift 

 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 tem- 

 perate 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 40°N and long. 35° to 55°W, 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. 



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