Why alligators?

We used alligators (Alligator mississippiensis) as our subjects in these studies. We chose alligators because we could do our experiments over a wide range of body sizes. Among our subjects were more than fifty laboratory-hatched and laboratory-raised animals ranging from about nine inches long to more than six feet long. Our hope was to clarify some speculations at the time about how blood flow might have affected the ability of large reptiles like dinosaurs to regulate their body temperatures.

The controversy was related to the "hot-blooded dinosaurs" controversy, which held that dinosaurs may have been warm-blooded like mammals and birds, and so were highly active and intelligent creatures.

At that time, there was a claim that dinosaurs did not need to be hot-blooded because control over blood-mediated heat exchange increased with large body size. Thus large animals could use their circulatory systems to heat very quickly and cool very slowly. Combined with the large thermal capacity of large animals, this would make dinosaurs essentially homeothermic without them having to resort to metabolically expensive heat production.

These claims were made from data measuring heating and cooling rates of alligators, which supposedly showed an increasing disparity between heating and cooling rates with increasing body size. For various reasons, these data were not convincing to me.

So, we decided to test this idea with our own collection of alligators.

Further reading

Smith, E. N. (1976). Heating and cooling rates of the American alligator, Alligator mississippiensis. Physiological Zoology 49: 37-48.

Smith, E. N. (1976). Cutaneous heat flow during heating and cooling in Alligator mississippiensis. American Journal of Physiology 230: 1205-1210.

Smith, E. N., S. Robertson, et al. (1978). Cutaneous blood flow during heating and cooling in the American alligator. American Journal of Physiology 235: R160-R167.

Smith, E. N., E. A. Standora, et al. (1984). Physiological thermoregulation of mature alligators. Comparative Biochemistry and Physiology 77A: 189-193.

Bakker, R. T. (2001). The Dinosaur Heresies: New Theories Unlocking the Mystery of the Dinosaurs and Their Extinction, Kensington Publishing Corporation.

Blood flow pages

Heat exchange

Why alligators?

What we did

What we found

Implications