Parsing handling time into its components: implications for responses to a temperature gradient

Area of Science:

• Ecology
• Ecological Physiology
• Predator-Prey Dynamics

Background:

• Functional response is crucial for predator-prey interactions and population dynamics.
• The metabolic theory of ecology (MTE) models temperature effects on handling time (Th), but underlying processes are unclear.
• Understanding Th variations is vital for predicting ecological community responses to climate change.

Purpose of the Study:

• To investigate the thermal responses of handling and digestion components of Th.
• To compare estimated Th with directly observed handling times across a temperature gradient.
• To clarify the influence of temperature on predator-prey interaction strength.

Main Methods:

• A ladybeetle-aphid system was used to study predator-prey interactions.
• Handling time was directly observed and compared with estimated Th values across a temperature gradient.
• Corrected digestion time was calculated by subtracting observed handling time from estimated Th.

Main Results:

• Estimated Th values were consistently higher than observed handling times.
• Corrected digestion rate increased exponentially with temperature, aligning with MTE predictions.
• Handling rate exhibited a hump-shaped relationship with temperature, contrasting MTE predictions.

Conclusions:

• The parameter Th conflates handling and digestion, which have distinct thermal responses.
• Discrepancies in Th thermal responses explain difficulties in identifying general patterns in previous studies.
• Accurate modeling of predator-prey dynamics under climate change requires separating handling and digestion processes.