<b>THE EFFECT OF HEAD-STARTING ON MORPHOLOGY AND BITE FORCE IN THE DIAMONDBACK TERRAPIN (<i>Malaclemys terrapin</i>)</b>
Reisenfeld, Kyra Andra
Head-starting is the captive rearing and care of animals through their juvenile life stage, followed by release into their native habitats. The goal of head-starting programs is to avoid high mortality of juveniles and thus increase overall population size by allowing more individuals to survive and achieve reproductive success. <i>Malaclemys terrapin</i> populations are declining throughout their range due to increased nest predation, road mortality, habitat loss, commercial harvest for food, and bycatch in crab pots. A <i>M. terrapin</i> head-starting program in the Chesapeake Bay suggested that survival of head-started animals is lower than wild animals. Physiological performance may affect an individual’s ability to gain resources and thus may affect individual survivorship. Bite force is one physiological performance measurement that is affected by diet and corresponding head and body morphology. Head-started <i>M. terrapin</i> are fed a pellet diet, which may yield individuals with different morphology, bite force and potential diet post-release. Bite force, head, and body morphometrics were collected from <i>M. terrapin</i> (n = 444) of all ages on Poplar Island, MD. A prediction model was used to calculate theoretical bite forces of <i>M. terrapin</i> (n = 1,637) across ontogeny from a historical dataset. The force needed to crush prey items in the Chesapeake Bay was obtained to determine potential diet of head-started terrapins post-release. I found that head-started terrapins are larger at time of release, and have greater bite force than wild terrapins at the same age. The greater bite force in head-started terrapins is observed until age 10. This difference may allow for a head-started terrapins to have a more diverse diet during ontogeny. Head-started terrapins have wider and taller heads, longer snouts, and shorter jaw in-lever at smaller body sizes. Head-started terrapins have shorter heads and shorter lower jaws across all body sizes. Smaller head-started terrapins had marginally greater bite force than wild terrapins. Bite force capacity of head-started terrapins does not explain the reduced survivorship of head-started <i>M. terrapin</i>. Our results show that head-starting may have long-term biological and ecological effects on a target species.