Prey–predator dynamics with adaptive protection mutualism

Prey can ease the burden of exploitation by attracting a third party that interferes with their predators. Such is the case for plant-ant or aphid-ant mutualisms , where the vic- tim supplies food to the ants, while the ants attack or drive away the offenders. Since ants are adaptive foragers, defense services can be altered by alternative food sources (e.g., other plants, or human-supplied resource). This article explores the prey-predator-ant sys- tem, using a model that combines predator-prey population dynamics with ant optimal foraging, where ants consume prey-supplied resources or alternative resources. Feedbacks between prey-predator dynamics and adaptive ant foraging leads to complex dynamics. For a given ant colony size and supply rate of alternative resources, prey can coexist with predators at alternative stable states, or along alternative limit cycles. Limit cycles extend the scope of defensive mutualism beyond the point where ants would abandon prey in favor of alternative resources under equilibrium conditions. These results highlight the im- portance of trait-mediated indirect interactions for natural mutualistic–antagonistic sys- tems, and potential outcomes of manipulating ant defense services using baits in the case of agriculture.