Temperature: Metabolic Aspects and Perception 



359 



and when the humidity decreases at a constant air temperature the reptile body 

 fails to cool significantly (Fig. 93). '^^ The body coat of horny scales is not 

 sufficiently permeable to water to permit much evaporation, although the 

 temperature of small snakes averaged 0.3° below air temperature in the range 

 from 10° to 30° C.^'° A series of reptiles, mostly snakes and large turtles, at 

 20-25° vaporized only 2-6 gm. HjO/kg./24 hrs.,'" in contrast to 76 gm. by 

 frogs. ^•'■^ 



Benedict has studied in detail the temperature relations and heat production 

 by reptiles, particularly large snakes.""' The metabolism is relatively constant 



7AM 



7AM 



7AM 



7AM 



7AM 



7AM 



7AM 



7AM 



. RECTAL TEMP 



<v ENVIRONMENTAL TEMP. 



n Ai^r!il h 



lo 



12 



14 



Fig. 92. Influence of changes in environmental temperature on rectal temperature 

 of a python snake. From Benedict.^® 



for various snakes at a given temperature; e.g., at 22°, it is 21-24 cal./m.-/24 

 hrs. The turtles produce more heat than do snakes or alligators, giant tortoises 

 producing several times as much as snakes. In snakes, lizards, and turtles the 

 heat production increases as the temperature rises. At 16° the level of heat 

 production of reptiles is similar to frog metabolism and may be higher than it 

 is in some fish.^^^ 



Many snakes and lizards absorb much radiant heat while basking in the 

 sunlight. Lizards in the sun at air temperature of 13° C. had a cloacal tempera- 

 ture of 38° C.^^ They may orient themselves to receive maximum radiation, 

 and it is reported that the chromatophores of some lizards are expanded during 



