WURSIC; and WURSIG BEHAVIOR AND ECOLOCY OF TURSIOPS TRI'XCATl'S 



ing kelp tossing, an animal would balance a piece 

 of Macrocystis sp. on its melon or forehead, flip it to 

 its tail with a sudden head jerk, flip it to the dorsal 

 fin with its tail, or any variation of the above. Kelp 

 tossing was observed nine times during the study, 

 and lasted an average of 15 min bout. 



Social Behavior 



Because most observations were done from a 

 distance, and usually only dorsal fins were visible 

 above the water, little insight was gained into 

 social behavior. Nevertheless, a few major trends 

 were apparent. When noisy leaps, noseouts. and 

 kelp tossing occurred, animals were also often 

 seen swimming side by side while touching, with 

 at least one of the animals in an upside down 

 position ("belly-up"). Viewed from directly over- 

 head, as when the subgroup passed close beneath 

 our observation cliff, individuals could be seen 

 nudging each others' bodies with their snouts. As 

 with leap frequency, most of this behavior was 

 observed in the afternoon (12 of 17 times. "Vi: 

 significant difference from morning at P<0.Q'2. 

 testing equality of percentages, Sokal and Rohlf 

 1969). It appeared as well that belly-up and rub- 

 bing behavior were more frequent when two sub- 

 groups which had moved separately for several 

 hours joined again. However, this did not happen 

 often enough (five times m total i for statistical 

 analysis. 



Five calves were observed during the study. 

 Each stayed close to a particular adult (see Wiirsig 

 1978), and we assume that this adult was the 

 mother. Calves and mothers were also observed 

 engaging in rubbing behavior with other adults. 



Bottlenose dolphins associated with the south- 

 ern right whale. Euhalacna glacialis, which were 

 seen near shore from June through November. 

 While moving along shore, dolphins veered from 

 their previous path by as much as 300 m to join one 

 or more right whales. Once with the whales, they 

 rapidly swam back and forth across the whales' 

 head. Whales invariably became very active when 

 dolphins were present, blowing and "snorting" 

 loudly in air as well as underwater. Whales also 

 rapidly surged or lunged ahead in the direction of 

 dolphins crossing their heads. The dolphins then 

 rode (or surfed) on the pressure waves created by 

 these lunges, riding along the crest of either wave 

 cascading to the side of the whales. This associa- 

 tion appeared to us to be play, and occurred 24 of 

 26 times (92'* ) that whales were directly in front 



of the path of moving dolphins. It lasted an aver- 

 age of 1.5 min.. after which the dolphins left the 

 whales and continued in the direction in which 

 they had been traveling beforejoining the whales. 



Further interspecific associations occurred with 

 the sea lion. Otaria flaret^cens, and, on one occa- 

 sion, with a subadult male elephant seal. Mlrotin- 

 f>a leontna. The pinnipeds joined a subgroup of 

 dolphins and traveled with it for up to 1 km. 

 rapidly moving among the dolphins. 



Dolphins also at times approached our 4.5 m 

 rubber Zodiac boat and swam underneath the boat 

 for brief (up to 5 min) periods. During 86 of 95 

 (9Kc) boat approaches, however, bottlenose dol- 

 phins appeared to ignore our boat, neither ap- 

 proaching nor avoiding it. 



When winds rose above 20-30 km h, dolphins 

 were often observed rapidly riding down the ad- 

 vancing crest of waves in the surfline. It appeared 

 that they were surfing the waves much as human 

 surfers do, and much as dolphins did with "bow" 

 waves of whales. 



Possible Predation 



We saw no direct evidence for predation on 

 bottlenose dolphins, but one of the animals, TS ( for 

 "tiger stripes," Wiirsig and Wiirsig 1977) ap- 

 peared in January 1975 with a series of scratched 

 lines along its left dorsum. From the regularity 

 and spacing of the lines, we bel ieve that they were 

 made by killer whale. Orriniis area , teeth. It seems 

 possible that this individual narrowly escaped a 

 killer whale. Furthermore, on two separate occa- 

 sions, we observed killer whales approaching 

 within 0.5 km of bottlenose dolphins. In each case, 

 the bottlenose dolphins rapidly swam away and 

 toward the open sea. Their swimming was so rapid 

 at these times that the dolphins leaped clear of the 

 water and covered 2 or 3 times their own length 

 out of the water during low forward leaps. Hertel 

 (1963) suggested from mathematical models that 

 this type of movement is most efficient for rapid 

 surface swimming. Theodolite readings taken at 

 these times indicate that the dolphins were mov- 

 ing at speeds of at least 30 km/h; however, no 

 definitive upper limit speed information was ob- 

 tained because it was difficult to follow rapidly 

 moving animals accurately in a .short- time period. 



DISCUSSION 



The bottleno.se dolphin population studied here 



407 



