SREL Reprint #3754

Association of size, climatic factors, and mercury body burdens with movement behavior in American alligators

Laura V. Kojima1,2, Michel T. Kohl3, Thomas R. Rainwater4,5, Benjamin B. Parrott1,2,
and Tracey D. Tuberville1

1Savannah River Ecology Laboratory, University of Georgia, P.O. Drawer E, Aiken, SC 29802, USA
2Odum School of Ecology, University of Georgia, 140 E Green St, Athens, GA 30602, USA
3Warnell School of Forestry and Natural Resources, University of Georgia,
180 E Green St, Athens, GA 30602, USA
4Baruch Institute of Coastal Ecology and Forest Science, Clemson University, Georgetown, SC, USA
5Tom Yawkey Wildlife Center, Georgetown, SC, USA

Abstract: Animal movement behavior provides insight into organismal and ecological function. These functions are often disturbed by anthropogenic influences, such as urbanization and habitat fragmentation, yet the effects of long-term exposures to environmental contaminants on movement have yet to be examined. The long lifespans and broad diets of crocodilians often lead to bioaccumulation of persistent contaminants and confer a marked vulnerability to consequent physiological effects. In this study, we investigate the relationships between blood concentrations of mercury (Hg), a widespread contaminant with well characterized neurotoxicity, and movement patterns in free living, naturally exposed American alligators (Alligator mississippiensis). We sampled adult male alligators from two former nuclear cooling reservoirs with different Hg contamination histories and placed GPS transmitters on a subset of individuals from each reservoir (13 total). Data collected over the ensuing two years were analyzed using a linear mixed effects framework combined with AICc model selection to resolve the relationships linking seasonal alligator movement (daily activity (s) and daily distance (m)) and home range to climate conditions, individual traits, and blood Hg concentrations (mg/kg; wet weight). We found that climate conditions, alligator size (snout-vent-length), and blood Hg concentrations all influence alligator daily activity but do not contribute to alligator daily movement (distance). Furthermore, we found that blood Hg concentrations were strongly correlated with seasonal home range size where individuals with elevated Hg had larger home ranges in spring, fall, and winter. These findings provide insight into how climate, anthropogenic contaminants, and individual traits relate to alligator movement patterns across seasons.

Keywords: Animal movement; Home range; GPS; Ecotoxicology; Crocodilian

SREL Reprint #3754

Kojima, L. V., M. T. Kohl, T. R. Rainwater, B. B. Parrott, and T. D. Tuberville. 2024. Association of size, climatic factors, and mercury body burdens with movement behavior in American alligators. Science of the Total Environment 921(170859).

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).