NORRIS and DOHL: BEHAVIOR OF THE HAWAUAN SPINNER DOLPHIN 



school the more frequent spins seem to be. In feed- 

 ing schools, which are the most dispersed of all 

 school formations, spinning and other high energy 

 aerial behavior occur almost continously. 



The leap. The most common aerial behavior in 

 which spinner dolphins actually leave the water is 

 the leap. Spinner dolphins perform leaps by burst- 

 ing from the water at about a 30° angle, rising a 

 meter or two above the surface, and falling back 

 into the water on the belly or side in a welter of 

 foam. Less frequently, reentry may be made 

 cleanly, snout first. 



Tail-over-head leap. The most active and 

 perhaps physically demanding aerial behavior 

 pattern is the tail-over-head leap and its variant, 

 the tail-over-head leap with spin. These aerial 

 patterns are seen only when the Spinner dolphin 

 school is most active. In this pattern the animal 

 bursts from the water at a rather high angle, 

 slings its tail over its head in a wide arc, usually 

 trailing a spiral of spray and enters tail first, often 

 slapping its flukes against the water with a loud 

 "thwack" in the process (Figure 7). On occasion 

 this may be accompanied by one or two revolutions 

 of a spin at the same time. 



Backslap. The emimal leaps about half or a 

 little more of its length out of water at about a 

 30°-45° angle, upside down. As it falls back, it 

 arches its body sharply, giving the water a sharp 

 slap wrjth the dorsal surface of its head and beak 

 (Figure 8). Backslaps are often performed in 

 slowly moving schools. 



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FIGURE 8. — A typical backslap of a spinner dolphin. As the 

 school moves slowly the dolphin emerges in the direction of 

 swimming, belly up, and arches its back at the last instant and 

 slaps its back against the water. 



Headslap. The reverse of the backslap. The 

 animal emerges in the normal position, once again 

 at about 30°-45° angle to the water surface, and 

 then flexes its head sharply downward, slapping 

 its chin and lower beak against the water (Figure 

 9). It is one of the most common patterns seen in 

 moving schools. 



FIGURE 7— The tail-over-head leap of 

 a spinner dolphin. This may, at times, 

 be combined with a spin. 



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