between the fluctuating pulmonary 

 blood flow and the fluctuating alveolar 

 gas composition (Otis, 1964): and 4) 

 the solubility of respiratory gases in 

 pulmonary tissue. The greatest differ- 

 ences we observed were A/'og = 36 

 mm Hg and A/coo ~ '^ "^^n Hg 

 (Figure 8): These considerable excur- 

 sions follow from the ratio of resting 

 lung volume to tidal volume, which 

 in the whale is about 2 and in man 

 about 5; the ratio of resting lung 

 volume to metabolic rate, which in 

 the whale is about 20 and in man is 

 about 10; and the very large differ- 

 ence between human and whale res- 

 piratory rates. Taken together, these 

 relationships suggest that apneustic 

 breathing in the whale is just as it 

 seems: each breath interrupts a res- 

 piratory pause which actually repre- 

 sents a period of breathholding, dur- 

 ing which appropriate changes occur 

 in arterial blood gas tensions. Al- 

 though tempting, approaches toward 

 cardiac output computation are ham- 

 pered by ignorance of the composition 

 of mixed venous blood. Calculations 

 of the "mean" alveolar gas or arterial 

 blood composition are similarly ham- 

 pered, and by imprecision in the 

 sample collection timing as well. 



CONCLUSIONS 



1. These two gray whale calves 

 have provided the first opportunity 

 for the collection of physiologic data 

 from living baleen whales. The growth- 

 rate in one of them was such that she 

 became the world's largest captive 

 animal. 



2. Comparison of their size with 

 that of whales in nature, and of their 

 growthrate with one another and with 

 other animals, strongly suggests that 

 their size and growthrate were normal. 



3. We observed increases in res- 

 piratory function and metabolism 

 during growth similar to the increases 

 in terrestrial mammals. In particular: 

 relative increases in body weight: and 

 of lung volume, minute ventilation, 

 and metabolic rate as functions of 

 body weight, proceeded in approxi- 



mate parallel to the relative increases 

 observed in man, 



4. Interspecies comparisons of ab- 

 solute lung volume and metabolic 

 rate can also be based on body weight. 

 Where the gray whale calves differed 

 from correlations drawn between mam- 

 mals including those at the extremes 

 of body size, the departure could be 

 explained by the whales' immaturity. 



5. One of the whales entered a 

 rapid growth phase, during which it 

 gained approximately 1,000 kg/mo. 

 Its gross efficiency for growth, cal- 

 culated from the amount it ate and 

 weighed, diminished from about 10 

 percent at a body weight of about 

 3,000 kg to about 7 percent at a body 

 weight of 6,350 kg. 



6. The relationships between tidal 

 volume, resting lung volume, and 

 wasted ventilation are similar in the 

 gray whale calf to these in other div- 

 ing mammals: although those rela- 

 tionships are different from the ones 

 in terrestrial animals, they follow 

 from the apneustic respiratory pat- 

 tern (of infrequent but very large 

 breaths interrupting long periods of 

 breathholding at high lung volume). 



7. The apneustic pattern of breath- 

 ing also results in respiratory excur- 

 sions in arterial oxygen and carbon 

 dioxide tensions much larger than 

 those predicted in terrestrial mammals. 



ACKNOWLEDGMENTS 



Both whales were kept in pools at 

 Sea World, Inc., an oceanarium in 

 San Diego, Calif. The staff and ad- 

 ministration extended to investiga- 

 tors courtesies and facilities both 

 large and small, ranging from hot 

 showers and coffee to underwriting 

 the expeditions and the subsequent 

 upkeep of the whales: and thereby 

 made these studies both possible and 

 enjoyable. In particular. Bud Dona- 

 hoo and Sue Bailey provided Gigi II 

 and her investigators with under- 

 standing and with expert assistance. 

 We acknowledge with thanks the sup- 

 port of Robert Peterson and the crew 

 of the FiilcDii involved in the capture. 



transport, and maintenance of Gigi I. 

 We are also grateful for the consider- 

 able assistance of Jack Schultz, Ken 

 Hamai, James Wright. Brian D' Aoust, 

 and Morgan Wells. Finally, we are 

 grateful to the two Gigis, for they, by 

 patiently enduring our several insults, 

 made possible observations new to 

 the largest and least accessible sub- 

 order of living mammals. 



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