36 



"Nose out" behavior usually accompanied Rafting". "Rafting" behavior is 

 where animals lie quietly at the surface, in most of the spotter schools, some 

 portion of the animals would begin to raft by the mid-point of the set. Rafts 

 seemed t<> consist most often of juvenile-adult pairs, which were gathered 

 together Into groups. The non-rafting animals normally spent most of their 

 time at the perimeter of the rafts. While rafting, "nose out" behavior occurred 

 much more frequently than it did among animals not in a raft. 



Spinners Underwater. — Spinner dolphins, as indicated in the surface behavior 

 section, spent nearly all of their time on the move, and groups were often seen. 

 Single sex groupings of adult males were frequently observed. Animals swam 

 close to one another and formed a synchronous diving group. Inter-animal 

 distance ranged from touching to about one meter. Spinners normally remained 

 segregated from the spotters and the two species were never seen swimming 

 together. 



Spotters Underwater. — Spotted dolphins also swam in small groups of 2 to 9 

 animals. The groups most often appeared to be family groups. They engaged 

 in touching behavior very commonly. Most often, the touching was with one 

 animal letting its flipper touch the dorsal surface or flanks of another. 

 Occasionally animals would rub against one another with various parts of 

 the body. On a number of occasions young animals were seen to position 

 themselves directly under an adult such that the flukes of the two animals 

 were aligned. The young animals appeared to be assisted in moving by this 

 method. 



Aggressive interactions took place quite frequently. Their frequency may 

 have increased as the net volume decreased reaching a maximum just as 

 backdown was beginning. The data on context of aggression, participants, and 

 timing are just beginning to be analyzed. 



BACKDOWN 



During backdown, the porpoise are compacted in a relatively narrow 

 environment. Virtually all group behavior, even including adult-young groups 

 to a large extent, seems to disappear. "Rafts" are the only recognizable 

 remaining behavior pattern. Since the Elizabeth C.J. is equipped with the 

 "Bold Contender and super apron" type of net. the backdown area is made of 

 1.25 inch mesh webbing. During backdown, some animals would bang repeatedly 

 into webbing without becoming entangled. One behavior observed frequently on 

 this cruise was "sleeping" behavior, a behavior originally observed by NMFS 

 personnel on an earlier cruise. It appears to be a general phenomenon which 

 may lead to considerable mortality. In "sleeping" behavior, porpoise are seen 

 to lie passively on the net bottom, very often in a ventral side upward position. 

 In standard nets the floor is so deep that these animals, when seen at all, 

 appear to be dead. In contrast, the super apron design creates a shelf, onto 

 which the porpoise are forced during backdown. "Sleeping" animals, on this 

 shelf, are easily seen by a person equipped with a face mask and snorkel, and 

 are even available to a person diving from the surface. Normally, "sleeping" 

 animals come to the surface within about 4 minutes, apparently to breathe. 

 At that time, they can be backed out of the net in the normal fashion. Crew 

 members working in the backdown areas, need to be informed of this behavior 

 and how to respond to it. 



With the super apron design, essentially all of the porpoise can be backed 

 out of the net. If a few animals remain in the net, they are easily removed by 

 personnel in the backdown area, when the net becomes very narrow. 



POST-BACKDOWN BEHAVIOR 



Upon release, the porpoise observed on this cruise were apparently im- 

 mediately aware that they were free. After going over the corkline, they 

 would make a fairly long, shallow dive and surface in a long, low leap, 

 making a large splash upon re-entry. Usually, all animals would head in one 

 direction on release, and they could be observed continuing high speed travel, 

 with the long leaps and large splashes, for a distance of over 1 to 2 km or 

 more. On some sets, there were two directions of travel after release, with 



