Predators, predators, and prey: A guide for survival

Algae, snails, and crabs. Grass, grasshoppers, and spiders. Shrubs, deer, and wolves.

These are all examples of tri-trophic food chains, comprised of prey, a middle predator, and a top predator.

The slightest change in any of the parameters in a tri-trophic food chain model can have profound effects on the ecology of the entire system, potentially even leading to extinction. To better inform ecological models that rely on these interactions, Kumbhakar et al. studied the wide-ranging impacts of the predator’s consumption rate.

By comparing three food chain models, the researchers uncovered different types of bistabilities — two stable sets of scenarios at which the species can coexist — and how sensitive these are to the way the species interact. Any modification in the predator’s behavior considerably affects the types of scenarios that can unfold, the probability of these scenarios, and the coexistence of the three species.

“The emergence of different types of bistability for different choices of functional responses has important implications in ecological modeling,” said author Nikhil Pal. “Since ecological data are rarely accurate enough to discriminate the functions as close as we have investigated, such structural sensitivity in bistability behavior could jeopardize any prediction by such models.”

The scientists plan to extend this study for disease transmission functions. This additional layer of intricacies in the interactions of susceptible and infected individuals can provide insights into epidemic dynamics and disease control strategies.

“This work illustrates how finely balanced species survival can be, and how sensitive that balance is to the way we represent interactions mathematically,” said Pal. “Even small differences in the curves used to model interactions can significantly affect the regions of extinction and coexistence, and the diverse dynamical scenarios.”

Source: “Structural sensitivity of a tri-trophic food chain model in a parameter plane,” by Ruma Kumbhakar, Saheb Pal, and Nikhil Pal, Chaos (2025). The article can be accessed at https://doi.org/10.1063/5.0275113 .