We know the body temperatures of reptiles vary with that of the air or
water in which they live, as they have no means of internal temperature
control. They are very sluggish when their body temperatures are low and
become more active as these temperatures rise, but only to a certain
point. If the body temperatures of reptiles become too high, they die in
a few minutes.
A group of physiologists from Columbia University spent nearly 2 months
in southern Florida experimenting on reptiles. They determined the rate
of rise of body temperatures of large lizards and alligators of all
sizes during exposure to the midday sun. As was expected, the smaller
the reptile the more rapid the rise in body temperature. Dinosaurs were
reptiles so we can make two assumptions: That their physiology was very
similar to that of living reptiles; and that the rate of rise of their
body temperatures from exposure to the sun would follow the principles
found for living reptiles.
By applying these principles to the dinosaurs, this group of scientists
calculated that if the great bulk of an _Apatosaurus_ were exposed to
the direct rays of the sun at an air temperature of 110° F. for 36 to 40
hours, its body temperature would rise only 1° F. Therefore, if these
calculations are correct, it is probable that the very size of the huge
dinosaurs operated to maintain a fairly constant body temperature.
Consequently, daily and seasonal temperature changes probably did not
affect the activities of the large dinosaurs. However, the activities of
the small ones may have been affected by the daily range in temperature.