on the bottom of the tank" by a juvenile male 

 Bontu, Inia geoffrensis. The occurrence of this be- 

 havior in /. geoffrensis and that observed in a 

 juvenile male Atlantic bottlenose dolphin was fre- 

 quent and apparently spontaneous tCaldwelF). 

 Pryor* and Norris et al. (footnote 1) have noted 

 instances where the passive-type behavior was 

 presumably induced in training situations where 

 Tursiops spp. were being "worked hard." These 

 animals would go to the bottom of the tank, emit a 

 quantity of air and might remain at the bottom for 

 several minutes. Norris et al. hypothesized that 

 this behavior may be similar to the "dearoused 

 state" described by Delius (1970) for terrestrial 

 animals, the most widely known example of which 

 is the feigning of death by the Virginia opposum, 

 Didelphis marsupialis . The major criticism (Nor- 

 ris et al.) of the dearousal hypothesis in the pres- 

 ent situation would seem to concern the 

 evolutionary value of such a response to a pelagic 

 air breathing animal that would tend to sink to- 

 ward the bottom in very deep water. One argu- 

 ment (Norris et al.) is that the situation which 

 elicits dearousal (purse seining) has been a factor 

 for only about 15-20 yr, and it is therefore not 

 necessary to hypothesize an adaptive value for the 

 behavior. To accept this hypothesis it would have 

 to be assumed that the capability for dearousal has 

 evolved in response to other circumstances. 



A second hypothesis to explain this behavior 

 relates to the effects of chase and capture on the 

 physiology of the dolphins. Possibly indicative is 

 the awkwardness of the swimming movements 

 displayed by the animals while "passive." Hart- 

 hoorn (1973) described the effects of chase and 

 capture on large African mammals. Long chases 

 using motor-driven vehicles result in a typical 

 condition termed "capture myopathy." Capture 

 myopathy is very common in the animals captured 

 for zoos and often causes a delayed mortality. 

 Symptoms include stiffness and awkward move- 

 ments. The method of capturing dolphin schools 

 involves a chase by speedboats that lasts up to 1.5 

 h and averages between 20 and 30 min. A chase of 

 that duration is capable of causing myopathies in 

 large terrestrial mammals which can be detected 

 by measuring changes in blood serum enzyme 



^David K. Caldwell, Director, Biocommunication and Marine 

 Mammal Research Facility, University of Florida, Route 1, Box 

 121, St. Augustine. FL 32084, pars, commun. October 1979. 



••Karen Pryor, former head animal trainer, Sea Life Park, 

 Hawaii; present address: 28 East 10th Street, New York, NY 

 10003, pers. commun. November 1976. 



levels (Harthoorn). A recent paper by Colgrove 

 ( 1978) documents a suspected case of myopathy in 

 a dolphin, Tursiops gilli = T. truncatus. This case 

 of myopathy appears to have been induced by the 

 stress of transporting the animal. Investigation of 

 blood chemistry of passive dolphins may allow de- 

 termination of whether capture myopathy does 

 occur as a result of chase and capture during the 

 tuna seining operation. 



Acknowledgments 



We thank Jack Hailman, Kenneth Norris, and 

 William Rogers for reviewing versions of this 

 manuscript. The photograph was taken by 

 Thomas Shay of the National Marine Fisheries 

 Service during the Cooperative Dedicated Vessel 

 Research Program cosponsored by the United 

 States Tuna Foundation, the National Marine 

 Fisheries Service, and the Marine Mammal Com- 

 mission. 



Literature Cited 



Caldwell, M. C, D. K. Caldwell, and W. E. Evans. 



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COLGROVE, G. S. 



1978. Suspected transportation-associated myopathy in a 

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1970. Irrelevant behavior, information processing and 

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Harthoorn, a. M. 



1973. Physiology and therapy of capture myopathy 2d 

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PERRIN, W. F 



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James M. Coe 

 Warren E. Stuntz 



Southwest Fisheries Center La Jolla Laboratory 

 National Marine Fisheries Service, NOAA 

 P.O. Box 271 

 La Jolla, CA 92038 



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