Vol. 5, p. 157-159. June 24, 1925. 



Occasional Papers 



OF THE 



Boston Society of Natural History. 



THE TIME OF SUBMERGENCE NECESSARY TO 

 DROWN ALLIGATORS AND TURTLES. 



BY GEORGE H. PARKER. 

 (Zoological Laboratory, Harvard University.) 



The waters of the Gatun Lake region are becoming infested 

 with the salt-water crocodile, Crocodylus-acutus Cuvier, which is 

 competing vigorously with the Central-American cayman, Cab- 

 man sclerops (Schneider). This cayman in the adult state is 

 now seldom seen about the banks of the great lake and its 

 affluent rivers but may still be found in the smaller streams and 

 forest pools. While I was at the Barro Colorado Island Labora- 

 tory in Gatun Lake, Panama Canal, I took the opportunity of 

 testing the caymans for the length of time they could remain 

 submerged in water. I had previously carried out somewhat 

 similar observations on the Florida manatee (Parker, 1922). 

 The manatee is of course a warm-blooded animal and remains 

 under water only a relatively short period, the longest voluntary 

 submergence observed being 16 minutes and 20 seconds. With 

 cold-blooded forms, like the caymans, much longer periods would 

 naturally be expected. Lumsden (1923, p. 365) states that 

 tortoises, turtles, alligators, and crocodiles sometimes remain 

 under water for an hour at a time and even when on land they 

 retain each breath for five to twenty minutes. He remarks 

 further (1924, p. 259) that tortoises resist attempts to chloro- 

 form them by simply refusing to breathe for two to three hours 

 at a stretch. These records support the prevailing idea that 

 cold-blooded, air-breathing animals may remain long periods 

 under water without suffocation. 



During my stay in Panama I succeeded in testing this capacity 

 in five caymans which ranged in length from 27 cm. to 86 cm. 

 Notwithstanding the differences in size all five animals behaved 

 in much the same way. 



The caymans were submerged under a wire net in a large glass 

 aquarium so that, though they had freedom to move about, they 

 could not reach the surface of the water to take air. Their 

 activities could be easily followed through the glass walls of the 

 aquarium. Immediately after submergence the caymans dis- 

 charged a number of bubbles of air from the nostrils and for 

 some time thereafter they swam about endeavoring to reach the 

 surface. This period of unsuccessful searching was commonly 

 followed by a lengthy interval of relative quiescence interrupted 



