BLUE WHALE (B) 



Balaenopteramusculus (Linnaeus 1758) 



Other Common Names 



Sulphur-bottom. 



Description 



Blue whales are the largest living mammals. Though 

 reports of maximum length and weight vary from one account 

 to another, Antarctic blue whales are known to have reached 

 lengths to 100 feet (30.5 m) and weights of over 150 tons 

 (136,363 kg]" before stocks were severely depleted by 

 whaling operations. North Atlantic blue whales may be 

 expected to reach lengths of 80-85 feet (24.4-25.9 m). In all 

 known populations of blue whales, females are slightly larger 

 than males of the same age. 



Viewed from above, the blue whale's rostrum is broad, 

 flat, and nearly U-shaped (actually shaped like a Gothic arch, 

 slightly flattened on the tip), with a single ridge extending 

 from the raised area just in front of the blowholes towards but 

 not quite reaching the tip of the snout. 



The dorsal fin is extremely small [to only 13 inches (33 

 cm)] and variable in shape from nearly triangular to 

 moderately falcate. In all cases, it is located so far back on the 

 animal's tail stock that it is seldom visible until the animal is 

 about to begin a dive. 



Blue whales are light bluish gray overall, mottled with 

 gray or grayish white. Some animals may have yellowish or 

 mustard coloration, primarily on the belly, the result of the 

 accumulation of diatoms during long stays in the cooler 

 waters to the north. The undersides of the flippers are light 

 grayish blue to white. 



The baleen plates are all black. 



Natural History Notes 



The blow or "spout' is tall, to perhaps 30 feet (9.1 m), 

 slender, vertical, and not bushy, as is the blow of humpback 

 whales, for instance. 



Although the blowing and diving patterns of blue whales 

 may vary, depending on the speed of movement and the 

 activity of the whale when it is encountered, they may be 

 generally described as follows: If the animal is moving slowly, 

 the blowhole and part of the head may still be visible when the 

 dorsal fin breaks the surface, and the animal may settle 

 quietly into the water without exposing the last portion of the 

 tail stock or the tail flukes. If the animal is moving more 

 quickly, however, or is about to begin a long dive, the 

 blowhole disappears below the surface, a broad expanse of 

 the back is exposed and disappears, and the dorsal fin 

 emerges briefly just before the animal lifts its tail stock and 

 flukes slightly above the surface before slipping out of sight. 



' The letter in parentheses indicates whether the species is a baleen (B) 

 or a toothed (T) whale. 



'° The largest measured specimen was "just over" 100 feet (30.5 m) ; the 

 largest specimen weighed, the 150-ton individual noted above, was 89 feet 

 (27.1 m) long. 



In this species it can be generally stated that the maximum 

 height of back in the area of the dorsal fin which is exposed 

 above the surface as the animal sounds is approximately four 

 times the height of the dorsal fin itself. The exposure of the 

 tail flukes is unlike that of the humpback whale (Fig. 39), the 

 right whale (Fig. 50), or the sperm whale (Fig. 57) in that 

 when beginning a long dive all these other species raise the 

 flukes high out of the water and usually descend at a steep 

 angle. Blue whales lift the flukes only slightly, if at all. 



Blue whales are relatively shallow feeders, feeding as 

 they do almost exclusively on "krill" (small shrimplike 

 crustaceans), most of which are distributed in the surface 

 330 feet (100 m). Blue whales usually occur singly or in 

 pairs. 



May Be Confused With 



At sea, blue whales may be confused with fin whales 

 (p. 26) and though the two are sometimes difficult to 

 distinguish from a distance, the following key differences 

 permit identification at close range: 



Blue Whale 



Fin Whale 



COLORATION 



Mottled bluish 

 and below. 



All black. 



gray above Gray above, white below; fre- 

 quently grayish-white chev- 

 ron behind head, right lower 

 lip white. 



BALEEN 



Bluish gray with yellowish- 

 white strips; front fifth to 

 third of baleen on right side 

 all white. 



HEAD 



Broad and nearly U-shaped; 

 all dark. 



Narrower, more V-shaped; 

 right lower lip white. 



DORSAL FIN 



To 13 inches (33 cm); triangu- 

 lar to moderately falcate; in 

 last third of back; visible well 

 after blow. 



To 24 inches (61 cm); falcate; 

 located slightly more than a 

 third forward from tail 

 flukes; usually visible short- 

 ly after blow. 



SURFACING AND PREPARING TO DIVE 



Often shows head and blow- 

 holes; broad expanse of back 

 and much later, dorsal fin. 



Usually rolls higher out of 

 water, particularly on long 

 dive; dorsal fin visible short- 

 ly after blow. 



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