Climate-induced shifts in crocodile body temperature impact behavior and performance

Area of Science:

• Climate change biology
• Herpetology
• Physiological ecology

Background:

• Anthropogenic climate change is increasing global energy, disrupting weather patterns and leading to temperature extremes.
• The El-Niño Southern Oscillation (ENSO) is expected to increase in variability, impacting predictable climate shifts.
• Ectotherms, like crocodiles, are sensitive to environmental temperatures, affecting their behavior and performance.

Purpose of the Study:

• To investigate how rising ambient temperatures affect the body temperature (Tb) and diving behavior of free-ranging estuarine crocodiles (Crocodylus porosus).
• To understand the physiological and behavioral responses of crocodiles to climate-induced temperature fluctuations.
• To assess the susceptibility of crocodiles to thermal stress near their critical limits.

Main Methods:

• Monitoring body temperature (Tb) and diving activity in 203 free-ranging estuarine crocodiles over 15 years (2008-2023).
• Correlating crocodile Tb and behavior with long-term air temperature trends and ENSO cycles.
• Analyzing the relationship between ambient temperatures, Tb, dive duration, and active cooling behaviors.

Main Results:

• Crocodile Tb has increased in correlation with rising air temperatures since 2008.
• Crocodiles experienced more days near their critical thermal limits (32°C-33°C).
• Increased temperatures led to reduced dive durations and elevated active cooling behaviors.

Conclusions:

• Estuarine crocodiles are susceptible to multi-year ambient temperature fluctuations driven by climate change.
• Current behaviors indicate crocodiles are operating near their physiological thermal limits.
• The long-term impact of future predicted temperature rises on crocodile populations remains uncertain.