Baby Got Bite: Kinematics and Ontogenetic Scaling of Bite Performance in the Northern Giant Musk Turtle ( <i>Staurotypus triporcatus</i> )

Body size strongly influences the life history, behavior, and ecology of vertebrates, yet few studies have quantified biomechanical performance across ontogeny, and turtles are rarely examined in this context. The Northern Giant Musk Turtle (Staurotypus triporcatus), which inhabits a wide range of wetlands throughout much of Central America, faces frequent predation attempts from crocodiles (Crocodylus moreletii and C. acutus) and consumes a diet dominated by hard-bodied prey (e.g., gastropods, palm seeds). Using a force transducer and high-speed camera, we quantified maximum bite performance and lunge kinematics across a broad size range and among five populations of Northern Giant Musk Turtles. Bite force scaled positively with straight carapace length but did not vary among populations or sexes, despite noticeable morphological variation among populations. Most morphometrics scaled with negative allometry relative to straight carapace length, except shell height, which scaled isometrically. These results suggest that increasing shell volume may be prioritized over other morphological traits, possibly reflecting the importance of shell morphology in surviving predation attempts, maximizing female reproductive capacity, or both. Additionally, lunge speed was independent of body size, suggesting that juveniles may compensate for their small size by lunging at velocities comparable to adults. Together, these findings highlight the complex scaling relationships of S. triporcatus and underscore the interplay between morphology, performance, and ecology in shaping survival and reproductive strategies.