NORMS and DOHL: BEHAVIOR OF THE HAWAIIAN SPINNER DOLPHIN 



On the lee side of Hawaii, the largest school was 

 centered at Keahole Point, ranging along about 23 

 km of coast, from Honokohau Harbor to Kiholo 

 Bay. In all, there are estimated to be about 200- 

 250 animals generally occurring in this area, and 

 they may be found in a single school at times or 

 fragmented into two or three smaller schools, 

 separated by a few kilometers of coastline. Here, 

 the dolphins do not seem to occupy any of the small 

 coves consistently, but to congregate over the 

 rather extensive area of shallow water, moving 

 back and forth. Not uncommonly, parts of this 

 aggregation moved during the day beyond the 

 limits listed above and may move as far as 

 Kailua-Kona or beyond, though the constant sea 

 traffic in that harbor seems to prevent normal 

 daily quiescence (defined below). We have termed 

 these animals collectively the "North Kona 

 School." Twenty-eight kilometers to the south, at 

 Kealakekua Bay, a school ranging from 2 to 70 

 animals (average 25 animals over 73 observa- 

 tions) was found. In our observations, dolphins 

 occurred in this bay on 74% of 113 observation 

 days. They most commonly occupied the deeply 

 indented bay but sometimes were found on the 

 shallow area north of the bay to Keauhou or occa- 

 sionally ne£u-ly to Kailua-Kona. Less commonly 

 they were found to the south in or near the very 

 small bays at Honaunau (City of Refuge) or 

 Hookena. 



The entire 56 km stretch from Hookena to South 

 Point seems not to harbor spinner dolphin schools 

 on a regular basis, though it should be noted that a 

 militau-y air closure zone prevented our flying over 

 the Milolii area regularly. We have a single record 

 of a 20 animal school at Milolii. This precipitous 

 coast drops abruptly into deep water, without 

 shallow areas alongshore. Much of the coast is 

 composed of relatively new lava flows from nearby 

 Mauna Loa volcano. 



Small schools, estimated generally at about 20 

 EUiimals, were seen, usually in very rough water, 

 at South Point, between Ka Lae and Honuapo, 

 over the modestly developed shallow area there, or 

 occasionally in the deep cove at Kaalualu. 



At Keauhou Cove, directly below Kilauea Cra- 

 ter, a small school (20-25 animals) was consis- 

 tently found. The dolphins came into very shallow 

 water there in an area protected by Keaoi Islet and 

 flanking coral heads, which produce a small area 

 of calm water along an otherwise rough water 

 coast. 



Cape Kumukahi, the easternmost point on the 



island, hosted a population of about 30 animals. 

 Several small irregular bays along the southern 

 edge of the cape form the "home bay" in this area, 

 with animals being noted at times as far as 

 Opilukao Cove. 



The largest school on the windward shore (ca. 

 100 animals) was often found at Kaloli Point, 18 

 km south of Hilo Bay. This location seemed also to 

 be the northernmost area of occupancy on this side 

 of the island. The dolphins were typically found in 

 the bay protected by the point and fringing coral 

 reefs. The rather shallow bay (maximum depth 20 

 m) is close to deep water to the south. 



The 112 km stretch of coast from Kaloli Point to 

 the north end of the island (Upolu Point) seemed 

 devoid of resident spinner dolphin schools. It is 

 also the site of the major sugar cane processing 

 plants on the island. Effluent from these plants 

 seems to produce murky waters along the coast 

 and clearly contributes to the long drift lines of 

 flotsam from processed sugar cane. Whether the 

 absence of animals and this activity are related is 

 unknown. 



At the north tip of Hawaii we occasionally saw 

 or heard of small schools of spinner dolphins 

 (10-30 animals) in the area between Kawaihae 

 Bay and Honoipu, though more often the entire 

 stretch of coast was found to be without animals 

 from the Kiholo Bay to the north tip at Upolu 

 Point. This circumstance is anomalous, in that 

 well-developed, shallow-water areas occur along 

 this shore, where schools might come during the 

 day, and where the sea is generally calm. 



REST AREAS 



Three features of the distribution of spinner 

 dolphins in the Hawaiian chain stand out. First, 

 the distribution is discontinous. Some coasts may 

 have several areas where dolphins congregate, 

 and others may have stretches of many kilometers 

 in extent where no amimals are seen. Second, cer- 

 tain coves or shallow areas are clearly regular 

 aggregation sites, while others seem to be used 

 much more infrequently. Third, some areas con- 

 sistently carry more animals than others. As we 

 will demonstrate, spinner dolphins come inshore 

 during daylight hours to enter a quiescent period 

 of some hours duration, and we think of these 

 congregation sites alongshore as "rest areas." 



What typifies such rest areas? First, all rest 

 areas are shallow sandy areas with <50 m depth 

 over part of their extent. They are usually com- 



827 



