Use of marine habitat and food resources by coastal inhabiting Alligator mississippiensis (American alligator): Implications for food web and community dynamics

摘要

The American alligator (Alligator mississippiensis) is a widespread aquatic predator throughout the southeastern United States. Historically, the ecological interactions of A. mississippiensis have been studied in the context of freshwater ecosystems such as inland lakes. Lacking salt secreting glands maintained in closely related crocodiles (Crocodylidae), the occurrence of A. mississippiensis in higher salinity marine and estuarine ecosystems has often been considered aberrant and of no particular importance to ecological processes in these coastal systems. However, it is well known that top-predators have the potential to exhibit strong effects within food webs through their interactions with prey and movement between disparate ecosystems. Within this dissertation, I set out to demonstrate that the use of marine and estuarine ecosystems by A. mississippiensis is common and that these behaviors have the potential to affect isolated freshwater ponds and wetlands by transferring marinederived nutrients and salt marshes through their interactions with an important mesopredator (Callinectes sapidus, Blue crab).;First, I employed field studies using nightlight surveys, stomach content analysis, and stable isotope analysis to assess intra-population variation in the use of marine habitat and food resources by A. mississippiensis inhabiting an Atlantic barrier island. Second, I used GPS/VHF telemetry to assess the effect of abiotic factors on crossecosystem movement patterns of adult individuals. Third, I attached and deployed animal-borne imaging systems (Crittercam) to quantify prey attack and capture success rates as well as diel activity patterns and investigated variation in these parameters. Lastly, I experimentally tested the potential of A. mississippiensis to elicit a trophic cascade within a simplified salt marsh food web through consumptive and nonconsumptive interactions with the mesopredator C. sapidus..;Results from this body of work will advance our understanding of the role A. mississippiensis serves in coastal ecosystems and provide essential data to predict consequences of changing environment conditions.