The Hawaiian spinner dolphin, Stenella longirostris: Effects of tourism.

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22 The highest frequency of aerial activities during the day occurs during arousal from rest (Norris and Dohl 1980). In completely quiescent spinner dolphin schools, arousal was marked by an abrupt aerial behavior such as a headslap or spinning leap (Norris and Dohl 1980). Schools were often fully alert within 10 minutes, with aerial activities occurring throughout the dolphin school (Norris and Dohl 1980). Swimming speed quickens as spinners enter a "zigzag swimming" period. Zigzag swimming consists of a period where dolphins exhibit great changes in their swimming speed, vocalizations, and social behavior while swimming back and forth within the bay. This activity culminates with the dolphins swimming toward the margin of the bay, and then back and forth, repeatedly entering and exiting the bay (Norris and Dohl 1980). Schools begin to traverse deep water as individual dolphins move towards the mouth of the bay at high speed. Dolphins gradually slow down as the mouth of the bay is reached and may mill about before moving back into the bay. At this point, spinner dolphins may return to their restful behavior within the bay or turn around and again swim towards deep water. Zigzag swimming typically lasts two to three hours and ends with fast swimming that takes the school beyond the confines of the bay. Aerial activities, aggressive chases and other social behaviors including mating are evident as the school travels towards the feeding grounds in deeper oceanic waters. As the school reaches the feeding grounds, subsynchronous dives begin (Norris and Dohl 1980, Norris et al. 1994a).
23 Aerial Behaviors Spinner dolphins are named for their spinning leaps. Spinning leaps are often performed in series by a single animal. The dolphin leaps from the water and completes up to five and one-half rotations around its longitudinal axis before crashing back into the water (Norris and Dohl 1980). Spinning leaps also involve a well-defined precursor pattern with stereotypical body movement and vocalizations (Norris et al. 1994a). This behavior is initiated by the spinner dolphin swimming horizontally for a few meters below the surface, making a rapid slicing motion with it's pectoral fins and emitting a series of barks. These rapid, jerky movements are followed by an upward arc that takes the dolphin out of water. When the dolphin is airborne, it throws its body into a twist, causing it to rotate along the longitudinal axis. Animals may spin vertically or horizontally in relationship to the water but hit the water on their backs or sides upon reentry. Spinner dolphins also exhibit at least six other aerial behaviors (Norris and Dohl 1980, Norris et al. 1994a). All but one of these, the arcuate leap, involves slapping the water upon re-entry. Arcuate leaps are made by fast-moving dolphins. These clean, arching leaps seem to improve efficiency of locomotion and produce little noise or bubbles upon reentry (Norris et al. 1994a). The salmon leap was named after its resemblance to salmon leaping up rapids or falls. Dolphins leap and fall back onto the water with slightly-arched (to the side) and stiff body. Salmon leaps are typically seen in fastmoving schools. The flip or tail-over-head leap is also an energetic/athletic leap that spinner dolphins perform (Norris et al. 1994a). Dolphins exit the water in a high arcuate leap
Page 1 and 2: 1 CHAPTER I INTRODUCTION Documented
Page 3 and 4: 3 avoid areas within 10 km of activ
Page 5 and 6: 5 displayed a significant reduction
Page 7 and 8: 7 a linear model, the vessel explai
Page 9 and 10: 9 decreasing their surface times (C
Page 11 and 12: 11 Hector's dolphins, Cephalorhynch
Page 13 and 14: 13 a killer whale (Herman and Tavol
Page 15 and 16: 15 The Marine Mammal Protection Act
Page 17 and 18: 17 Dearden 1993, Thompson et al. 19
Page 19 and 20: 19 dorsal surface and a white ventr
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Page 25 and 26: 25 Norris and Dohl 1980). Increases
Page 27 and 28: 27 CHAPTER III OCCURRENCE AND BEHAV
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Page 37 and 38: 37 Most human activities that were
Page 39 and 40: Table 1 39
Page 41 and 42: 41 Discussion Norris et al. (1994 )
Page 43 and 44: 43 The correlation between number o
Page 45 and 46: 45 to perform. If the dolphins do,
Page 47 and 48: 47 times motor boats approached and
Page 49 and 50: 49 On one occasion, a swimmer obser
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Page 55 and 56: 55 Figure 15. Square root of aerial
Page 57 and 58: 57 Figure 18a. Spinner dolphin surf
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Page 65 and 66: 65 Figure 25a. Square root of aeria
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73 morning than in the afternoon, t
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75 used by some boat operators resu
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77 reduced energy levels, then incr
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79 LITERATURE CITED Acevedo, A. 199
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81 Cooke, J. 1991. Classification a
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83 Gordon, J. and Moscrop, A. 1996.
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85 Montero, R., Martin, V., Heimlic
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87 Associates Inc., Bryan, Texas. F
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89 Wells, R. S. and Norris, K. S. 1
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The Hawaiian spinner dolphin, Stenella longirostris: Effects of tourism.

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