170 



THE BIOLOGY OF MARINE ANIMALS 



(homoiotherms) and resistance to pressure and pressure effects (deep- 

 diving whales). 



Physiological information is very scanty for all marine reptiles. The 

 possibility of bucco-pharyngeal and cloacal respiration requires considera- 

 tion. Quantitative studies on typical marine reptiles will have to be carried 

 out before their respiratory needs can be evaluated. Sea snakes and turtles 

 are said to survive many hours under water (Table 4.7). 



Diving marine birds usually stay under for only brief periods, from 1-2 

 min, but can stand submergence up to 6-12 min (guillemot, penguin, etc.). 

 Seals remain submerged up to 15 min. Compared with these times the 

 duration of dives in some whales is striking: about half an hour in fin and 

 humpbacked whales, and 1-2 hours in Greenland, bottle-nosed and sperm 

 whales (Table 4.7). 



TABLE 4.7 

 Duration of Submergence of Marine Reptiles, Birds and Mammals 



Sources: Murphy (117); Irving (82); Scholander (140); Witherby, et al. (168); Norman and Fraser (119); 

 Gunther (73); Layne (102) et al. 



Respiration in diving birds and mammals does not differ fundamentally 

 from that in typical air breathers. Adaptations which allow divers to 

 remain submerged for long periods are diminished sensitivity to C0 2 , 

 shunting of blood to essential organs, and ability to contract a large oxygen 

 debt. 



