Bone growth in the alligator is a cyclic phenomenon that is denoted by distinct growth rings between bony layers, similar to the annual growth rings commonly seen in tree trunks. These rings are most obvious in long bones, such as the humerus and the femur; histologic sections of the diaphysis of the femur were used in this study. Slide sections were prepared using standard histologic technique, with H and E and VVG stains. Rings on each femoral section were counted, and distance was measured from the innermost ring to the endosteum. Difficulties encountered in this exercise were: converging and diverging rings, discontinuous rings, faint versus distinct rings, duplicate rings and no obvious rings (homogeneous-appearing histological section with no distinct layering). These anomalies are believed to be due to nonseasonal bone resorption and remodeling during times of stress, illness or reduction in nutrient supply.

The Texas Department of Parks and Wildlife provided the bones from 125 animals and they have provided data on the body length and sex on each alligator specimen that was submitted for histology. The number of growth rings and the distance from the endosteum to the innermost ring was correlated with the Department's data to attempt to produce a statistical data base from which approximate age can be extrapolated. The rings are believed to be annual; this belief is substantiated by various other studies, which found a definite correlation between the number of growth rings and the actual age in other species of reptiles and several species of mammals. This information will be used in statistical methods of managing harvesting and replacement of alligators in Texas.