in front of the blowhole to near the tip of the snout. (The humpback 

 uhale's median rostral ridge is obscured by numerous knobs - resem- 

 bling over-sized rivets — scattered about the head, some of which are 

 located along the midline!. In Brvde's uhale, the single head ridge 

 characteristic ot the other rorquals is supplemented by two auxiliary 

 ridges, one on each side of the main ridge. Faint lateral ridges can 

 sometimes be detected on the rostra ot fin and blue whales. Recent 

 studies have revealed intergrades of a number of features of this group 

 (e.g., ridges and baleen characteristics), which sometimes confound 

 identification even when fragments of a specimen are in hand. 



At sea, these whales often appear very similar and must be examined 

 carefully before they can be identified with confidence. Observers 

 should not teel overly disappointed about not being able to make a 

 reliable idetification. There is enough overlap in the behavior ot these 

 whales and in the appearance ot their surfacing profiles to dictate 

 caution in using any single haracteristic for positive identification. 

 Depending on the animal's activities, the following features may be 

 useful in distinguishing the balaenopterids from one another: ij the 

 size, shape, and position of the dorsal fin and the timing of its 

 appearance on the surface relative to the animal's blow (in general, the 

 larger the whale, the smaller the dorsal fin, the farther back its position, 

 and the later its appearance on the surface after the animal's blow 1; 2 ) 

 the height of body in the area ot the dorsal fin which is exposed as the 

 animal sounds, relative to the size of the dorsal fin; ; ) sometimes the 

 blow rate and movement patterns; and 4) the shape and color ot the 

 head. 



The sixth species, the sperm whale, is a toothed whale. It has a low, 

 humplike dorsal ridge which, from certain views, particularly when the 

 animal is humping up to begin a dive, may be clearly visible and very 

 "dorsal-fin-like." At other times, particularly on some animals, it may 

 be rather indistinct. Because the profile of its hump and the knuckles 

 along its spine are often very prominent, the sperm whale has been 

 classified with the large whales possessing a dorsal fin. 



The sperm whale has a huge ponderous head ( in relation to body 

 size) and perhaps the most distinctive blow ot all cetaceans, emanating 

 as it does from a blowhole that is displaced to the left of the head near 

 the front. The blow projects obliquely forward and to the animal's left. 

 This blow seen under ideal conditions ^no wind) positively dis- 

 tinguishes a large whale as a sperm whale. Remember, however, that 

 wind conditions may affect the disposition and duration of the blow of 

 any species and that a single character alone is seldom sufficient to 

 permit positive identification. 



Since behavior by members of the same species ofiien varies from 

 one encounter to the next, an observer can greatly increase the 

 reliabilit\' of his identification by forming the habit of working 

 systematically through a set of characteristics tor the species rather than 

 depending on any single characteristic. 



Illustrations in the Large Whales section are at a scale of 1:120 



Body very large, up to 26 m long. 



Body basically bluish-gray with grayish-white mottling. 



Baleen, palate, and tongue all black. 



Head broad and nearly U-shaped, viewed from above. 



Head flat in front ot blowhole, viewed from side. 



Dorsal fin small (up to 'Am high), triangular to moderately falcate 



in the last one-third of back. 

 Distribution from tropical to subarctic seas. 

 Flukes occasionally raised before long dive. 



Blue Whale 



Balamoplera musculus (A) 



Body large, up to 24 m long.Body mostly dark gray or brownish- 

 gray; belly and undersides of flukes and flippers white; grayish- 

 white chevron frequently on back behind head. 



Right lower lip white; right upper lip sometimes white; left lips dark 



Head long and V'-shaped, viewed from above. 



Right front one-third to one-fifth of baleen yellowish white; other 

 baleen bluish-gray with yellowish-white stripes. 



Dorsal fin to Vim high, slightly more than one-third forward from 

 fluke notch; usually arises from back at angle of less than 40 . 



Distribution more northerly during summer. 



Flukes not raised on dive. 



Fin Whale 



Bulaenoplcra physalus (A) 



37 



