On the use of functional responses to quantify emergent multiple predator effects

Area of Science:

• Ecology
• Community Ecology
• Predator-Prey Dynamics

Background:

• Non-independent predator interactions significantly influence ecological community structure and dynamics.
• Multiple predator effects (MPEs) can alter prey mortality through facilitation or interference.
• Traditional models like the multiplicative risk model are limited by assumptions of linear functional response and no prey depletion.

Purpose of the Study:

• To compare the strengths, limitations, and predictions of three approaches for detecting MPEs: multiplicative risk, direct functional response (FR), and population-dynamic models.
• To identify biases in existing methods and propose a more robust approach for analyzing predator interactions.

Main Methods:

• Utilized simulated datasets to evaluate the performance of three distinct ecological modeling approaches.
• Assessed model predictions regarding predation rates and the detection of risk reduction under varying prey densities and depletion levels.

Main Results:

• The multiplicative risk and direct FR models yielded similar predictions, underestimating predation rates at high prey densities or substantial prey depletion.
• These two models frequently failed to detect predator risk reduction.
• Parameters from the direct FR approach lacked mechanistic interpretability, hindering understanding of MPE mechanisms.

Conclusions:

• The population-dynamic approach is recommended as a robust, precise, and scalable mechanistic framework for detecting and quantifying MPEs.
• This approach overcomes the limitations of traditional and direct FR models, providing deeper insights into predator interactions.