Juvenile American Alligators (Alligator mississippiensis) Use Behavioral Thermoregulation to Cope with Dehydration and Salt-Loading when Chronically Exposed to 12 ‰ Saltwater

Abstract

American alligators (Alligator mississippiensis) are native to freshwater habitats in the Southeastern United States. These areas are susceptible to salinity increases due to extreme weather events (e.g., hurricanes) and climate change. The goal of this study was to investigate behaviors in juvenile alligators exposed to 12‰ saltwater for five weeks. Sixteen alligators were maintained in an experimental tank with 90 L of water and a heat lamp overhanging a basking plate. Observations were conducted in freshwater (prior to exposure to saltwater) and over the course of 5 weeks in 12‰ saltwater. This allowed for comparison of behaviors in freshwater and in saltwater in the same group of animals. Behaviors related to thermoregulation (basking and staying in the water) and feeding were recorded via instantaneous sampling, in which sampling intervals of 1 min occurred throughout a 20 min observation period. Saltwater-exposed alligators reduced foraging and feeding within the first week of saltwater exposure and spent significantly less time basking compared with freshwater observations. Furthermore, significantly fewer animals chose to bask over the course of 5 weeks in saltwater. A novel behavior, never seen in freshwater, was the closing of the outer eyelids when alligators were in the saltwater. Collectively, the present study demonstrates that chronic saltwater exposure has significant impact on the thermoregulatory behavior in juvenile alligators concomitantly exposed to dehydration and salt-loading without access to freshwater. As alligator hatchlings emerge during peak hurricane season, the survivability of hatchlings may be compromised if access to freshwater is unattainable.