ERICKSON, G.M.; LAPPIN, A.K.; VLIET, K.: Ontogeny of bite-force performance of the American alligator, Alligator mississippiensis

The diet of the American alligator, Alligator mississippiensis, undergoes substantial change during ontogeny. Hatchlings typically prey upon insects and small fish. At about 0.4 m total length, frogs and reptiles as well as crustaceans are added to the diet. At approximately 1.0 m, birds and small mammals become foodstuffs. Alligators over 1.5 m frequently feed on turtles, which have rigid integuments. Large adults over 3.0 m will prey upon large and powerful prey, such as deer and hogs. The dietary ontogeny of A. mississippiensis suggests that bite-force performance may not scale isometrically with body mass. Isometric growth predicts that muscle cross-sectional area should scale as mass to the 0.66 power. Given that muscle cross-sectional area determines muscle force generation, isometric growth predicts that bite-force performance also should scale as mass to the 0.66 power. Alternatively, elastic similarity theory predicts that bite force should scale as mass to the 0.75 power. Using a size series of force transducers, we measured the unilateral bite-force performance of American alligators with body masses from 100 g to nearly 300 kg. The bite forces generated by these animals ranged from 20 N in hatchlings to over 9,400 N in a large adult. Regression analysis shows that bite-force performance scales as mass to approximately the 0.75 power, in agreement with the prediction of elastic similarity theory. This suggests that bite-force performance may become increasingly important as alligators grow due to changes in diet. Non-isometric growth of relative cranial dimensions may explain this pattern.