Comparison of bite-force performance between long-term captive and wild American alligators (Alligator mississippiensis)

Abstract

Nearly all animals show altered musculo-skeletal phenotypes when subjected to captive conditions. Whether such changes affect biomechanical performance is for the most part unknown. In American alligators Alligator mississippiensis such modifications include shortened jaws, more robust body form, and broadened heads. Bite-force performance was assessed for a variety of sizes of wild-captured alligator specimens and the results correlated with morphological indices. Bite forces ranged from 217 to 13 172 N, with the latter being the highest value ever measured for a living animal. These data were statistically compared with those for long-term captive specimens using ANCOVA. Bite-force performance showed similar patterns of increase between captive and wild-reared animals, and bite forces with respect to snout–vent length and body mass were statistically indistinguishable. Nevertheless, with respect to head size, captive alligators were found to bite more forcefully than their wild counterparts. These findings illustrate the importance of considering biomechanical performance differences between wild and captive individuals if meaningful ecological ties are to be made. Furthermore, before concluding that wild-reared or captive animals show similar or different biomechanical performances, it is important to understand that standardization to different morphological parameters can reveal conflicting results. Consideration as to which measures are the most germane to the question at hand is essential.