Nutritional effects on chemical defense alter predator–prey dynamics

Abstract

Reservoir-based chemical defense (= reducible defense) is a widespread mechanism to repel predators in many invertebrates. We investigated the influence of macronutrients on the availability and regeneration of defensive secretions and parametrize a theoretical functional response model for reducible defense to predict nutritional effects on predator–prey dynamics. Our modeling approach showed that initially high amounts of defensive secretions provided an effective short-time defense, while higher regeneration rates were favorable under permanent predation pressure. Regeneration rates were correlated to the amount of dietary fat and carbohydrates, indicating an adaptive connection of macronutrients on chemical defense and predatory success—an effect covering two trophic levels. Our results underpin the urgent need to integrate dynamical aspects of chemical defense into the modeling of predator–prey interactions in food webs.