Similar Conditions With Opposite Effects: Predation-Risk Effects on Prey Abundance Are Highly Contingent

Area of Science:

• Ecology
• Behavioral Ecology
• Population Dynamics

Background:

• Predation risk influences prey fitness, but effects on prey abundance are context-dependent.
• Generalizing predation risk effects across diverse environmental conditions is challenging.
• Previous studies often control single factors, limiting understanding of natural complexity.

Purpose of the Study:

• To investigate the context dependence of predation risk effects on prey abundance.
• To assess how variations in experimental conditions influence risk effects.
• To determine if risk effects are generalizable across different experiments.

Main Methods:

• Conducted multiple experiments under similar conditions, objectives, and measurements.
• Utilized diverse prey assemblages (≥11 taxa) across multiple prey generations.
• Analyzed variations in the magnitude and direction of risk effects among experiments.

Main Results:

• Predation risk effects on zooplankton density varied from negative to positive between experiments.
• Some species exhibited significant effects in one experiment and none in another.
• Results highlight profound context dependence of risk effects on prey populations.

Conclusions:

• Predation risk effects on prey abundance are highly context-dependent.
• Observed risk effects in one study may not apply to the same species in the same system.
• Mechanisms underlying opposite effects of risk on prey warrant further investigation.