How turtles keep their cool: Seasonal and diel basking patterns in a tropical turtle

Area of Science:

• Ecology and Evolutionary Biology
• Herpetology
• Behavioral Ecology

Background:

• Behavioral thermoregulation is crucial for ectotherm physiological performance.
• Previous studies suggested nocturnal basking in Krefft's river turtles (Emydura macquarii krefftii) may help avoid high water temperatures, but field evidence was lacking.

Purpose of the Study:

• To investigate the influence of environmental temperature on seasonal and diel basking patterns in Krefft's river turtles.
• To test the hypothesis that nocturnal basking is a strategy to avoid high water temperatures in a tropical population.

Main Methods:

• Utilized wildlife cameras for continuous monitoring of turtle basking events over a year in tropical north Queensland, Australia.
• Recorded simultaneous air and water temperatures using data loggers.
• Employed a negative binomial mixed effects model to analyze basking duration across different thermal conditions relative to the population's preferred temperature (26°C).

Main Results:

• Basking behavior was significantly influenced by the interplay between air and water temperatures.
• Turtles basked less during the day when both air and water temperatures exceeded their preferred range.
• At night, turtles increased basking duration when water was warm and air temperature was cool relative to their preferred temperature.

Conclusions:

• Krefft's river turtles exhibit significant heat avoidance as a thermoregulatory strategy.
• Nocturnal basking appears to be a mechanism to escape unfavorable high water temperatures in tropical environments.
• Findings contribute to understanding thermoregulatory behaviors in tropical reptile populations.