Nursing has seldom been seen in nature. In one 

 clifflop observation, a 60-animal school swam be- 

 low, containing a group of adult-calf pairs. One of 

 these pairs engaged in nursing. The adult turned 

 slightly on her side as the young dolphin 

 positioned itself obliquely alongside with its beak 

 pressing against her at the mammary slits. The 

 behavior persisted for a few seconds before the 

 animals dove. The posture was like that reported 

 in captive dolphins (Dohl et al. 1974). 



For 33 days in February-March 1970, a female 

 pair was seen in Kealakekua Bay and nearby 

 Keauhou. Unlike most such pairs, the two often 

 swam near our observation vehicle. The calf had 

 the distal 5-6 cm of its rostrum broken through 

 and bent to the side with some ragged flesh ex- 

 posed. In spited of this apparently grievous wound 

 the calf appeared active and well nourished. Con- 

 tact was very frequent between mother and calf. 

 Both the adult and calf used their flukes, flippers, 

 and dorsal fin to achieve this contact. On two occa- 

 sions the young animal touched its dorsal fin to the 

 adult's flank, laid its flukes up under and touching 

 hers, and held this position as their combined tail 

 beat propelled them both along. The young animal 

 rode both above and below the adult, sometimes 

 directly beneath her midbelly, occasionally slid- 

 ing backward until the moving flukes of the adult 

 tapped against its dorsal fin. In our observations 

 we never noted true assisted locomotion as de- 

 scribed by Norris and Prescott (1961), though 



FISHERY BULLETIN: VOL. 77. NO. 4 



swimming speed was generally so slow that it 

 might not be expected. 



A common posture was for the baby to swim 

 below and a little to the side of the big female, at 

 which time she placed her flipper against the 

 young animal's back, just anterior to its dorsal fin. 

 Much of the time the pair in this position swam in 

 synchrony, turning and diving together. 



On occasion the young animal swung away from 

 the adult for a few meters but soon turned, in- 

 creased speed, and rushed back to her. Once, dur- 

 ing a particularly long sortie, the adult pursued 

 the calf, slapped its back with her flukes, and then 

 the pair dove together. 



Sexual Associations 



At times, both on a given day and over several 

 days time, specific subgroups of 2-6 spinner dol- 

 phins whose members could be individually rec- 

 ognized, were seen together from the viewing cap- 

 sule. It was possible to determine the sex of some of 

 the animals. Sexually related behavior was exhib- 

 ited between male and male and male and female 

 pairs. It takes several forms. What Bateson (see 

 footnote 5) called "beak propulsion" was noted 

 (Figure 17). In it one animal swam up from below 

 another and inserted the tip of its rostrum into the 

 genital slit of the upper animal, apparently push- 

 ing the passive animal along. Both the dorsal fin 

 and the flippers are commonly used to stroke or 





gg^ 





FICURE 17.— Beak propulsion by a captive pair of spinner dolphin.s at Sea Life Park, Hawaii. An adult female is pushing an adult male. 

 844 



