HAIN ET AL.: FEEDING BEHAVIOR OF HUMPBACK WHALE 



tended lower jaw above the surface are quite 

 gradual. In several instances, humpbacks were 

 observed feeding in this manner (the slow, grad- 

 ual rise) in formation. Five or six whales ar- 

 ranged side by side and slightly staggered of one 

 another acted in unison. This behavior has been 

 similarly described from Alaskan waters and 

 termed "echeloned" lunge feeding (Jurasz and 

 Jurasz 1979). 



Inside Loop Behavior 



On 23 May 1980, a single humpback was ob- 

 served feeding for over 1 h. The whale repeatedly 

 displayed a behavior we have termed an "inside 

 loop." As the whale begins a shallow dive, it 

 sharply strikes the water's surface with its 

 flukes. This action creates an area of turbulence 

 in the water estimated to have an average diame- 

 ter of 9 m. This area of foam and bubbles is seen 

 clearly as the whale swims away at a shallow 

 dive angle with the pectoral fins held horizon- 

 tally. The whale, swimming rapidly, then rolls 

 180°, so that the white ventral surface of the 

 flukes can be seen just below the surface. An in- 

 side loop (a sharp U-turn in the vertical plane) 

 follows immediately, so that the whale is now 

 swimming toward the area of turbulence. Fi- 

 nally, the whale is seen rising vertically in a slow 

 lunge, with mouth widely agape, through the 

 center of the turbulence created by the fluke 

 slap. The horizontal distance covered by this 

 "out-and-back" motion was on the order of l%-2 

 body lengths of the whale. The behavioral se- 

 quence is illustrated diagrammatically in Figure 

 2. 



Several variations on the basic behavior were 

 observed. The humpback did not feed through 

 the area of turbulence in every instance. Occa- 

 sionally, the whale would surface to the side of 

 the disturbance, not always feeding. On other 

 occasions, a second whale would enter the gen- 

 eral area and subsequently be seen lunge feeding 

 through the disturbance created by the flukes of 

 the first whale, either alone or in unison with the 

 original whale. 



The inside loop behavior, observed on a single 

 occasion, involving a single whale later joined by 

 a second, is at present considered relatively un- 

 common. 



Bubbling Behaviors 

 Underwater exhalations or bubbling behav- 



iors were seen in association with feeding, or 

 apparent feeding, in 52% of our feeding observa- 

 tions. These exhalations appear to be of two ma- 

 jor types, forming what we have termed "bubble 

 columns" and "bubble clouds." In general, 

 bubble columns and bubble clouds have been 

 observed with about equal frequency. 



BUBBLE COLUMNS.-Bubble columns are 

 formed by the underwater exhalations of a whale 

 swimming from 3 to 5 m (estimated) below the 

 surface. As the bubble bursts are released, they 

 rise vertically to the surface in the form of a 

 somewhat ragged column. The columns are 1-2 

 m in diameter and are composed of random-sized 

 bubbles estimated to be generally >2 cm. Series 

 of from 4 to 15 bubble columns are used to form 

 rows, semicircles, and complete circles or bubble 

 nets (Figs. 3, 4). 



JV> 



B 







Figure 2.— "Inside loop" type of feeding behavior. A. Upon 

 making a shallow dive, humpback whale strikes the surface 

 sharply with flukes. B. Fluke slap creates an area of turbu- 

 lence (foam/bubbles) as whale swims away in a shallow dive, 

 flippers held horizontally. C. Whale executes a 180° roll and 

 now does a sharp inside loop, or U-turn in the vertical plane. 

 D. Whale lunge feeds through the area of disturbance created 

 by original fluke slap. 



261 



