GROWTH-RATE AND PLASMA-CORTICOSTERONE LEVELS IN JUVENILE ALLIGATORS MAINTAINED AT DIFFERENT STOCKING DENSITIES

Sixty‐six captive‐reared, juvenile alligators maintained in environmentally controlled chambers were randomly assigned to four treatments consisting of stocking densities of 0.35, 0.18, 0.12, and 0.09 m2/alligator. Alligators were maintained at these densities for 3.5 months. At approximately 4 week intervals the alligators were weighed, measured, and bled via cardiac puncture. Duplicate aliquots of plasma were assayed for corticosterone. All of the alligators continued to grow during the experiment, but alligators maintained at the lowest stocking density were significantly heavier and grew significantly faster (P < 0.01) and had significantly lower plasma corticosterone (P < 0.01) than alligators maintained at the highest stocking density. These results indicate that crowding (i.e., high‐density rearing) of juvenile alligators inhibits maximum growth and that the subsequent stress associated with this crowding results in chronically elevated plasma corticosterone. Plasma corticosterone showed a strong negative correlation with change in body weight; the faster the rate of growth, the lower the hormone levels. These results also show that a single blood sample taken at monthly intervals is sufficient to monitor chronically elevated plasma corticosterone in this species. Copyright © 1990 Wiley‐Liss, Inc., A Wiley Company