Revisiting Thermal Gradient Experiments: Effects of Thermal Heterogeneity on Salamander Behavior

Area of Science:

• Ecology
• Animal Behavior
• Physiology

Background:

• Thermal gradient experiments are common for studying ectotherm thermoregulation and inferring habitat preferences.
• Interpreting laboratory thermal gradients requires careful consideration of an organism's natural thermoregulatory strategies.
• Amphibians, often thermoconformers, may exhibit different responses in thermal gradients compared to heliothermic ectotherms.

Purpose of the Study:

• To investigate the thermoregulatory behavior of the Eastern Red-backed Salamander (Plethodon cinereus) in a controlled thermal gradient.
• To compare the salamander's response to a heterothermal gradient versus a homothermal control arena.
• To evaluate the assumptions of positive thermotaxis and thermal preference in ectotherm studies.

Main Methods:

• The study utilized a heterothermal gradient arena and a control homothermal arena.
• Behavioral responses of Plethodon cinereus were observed in both arena types.
• Movement patterns and temperature selection were recorded for each salamander.

Main Results:

• Salamanders in the control arena moved randomly towards the ends.
• In the thermal gradient, salamanders exhibited avoidance of the highest temperatures.
• No evidence of positive thermotaxis towards a specific preferred temperature was observed.

Conclusions:

• Plethodon cinereus demonstrates limited thermoregulatory behavior, primarily heat avoidance, not active temperature selection.
• Laboratory thermal gradient results for thermoconformers like amphibians may not equate to a 'preferred' temperature.
• Re-evaluation of terminology and experimental design is needed for interpreting ectotherm behavior in thermal gradients.