Behavioral games and emergent population dynamics

Jacob Emil Friis Frølich: Why the big bad wolf went hungry

If the story of the three little pigs were to happen in the world of theoretical ecology, it would go something like: Three little pigs went out to forage after building their houses. The big bad wolf arrives. The three little pigs keep foraging and proceed to be eaten. Apart from being a slightly less exciting story, we know that it does not correspond to reality. In reality, the behavior of both prey and predators is dynamic, dependant on the environment, the presence of the counterpart and their opponents foraging behavior. Most population models in marine ecology do not take this into account, and instead assume constant behavior. In the real world, the behavior of both prey and predators is dynamic, depending on many variables such as the environment, the presence and foraging behavior of their counterpart.

For instance, the interaction between predator and prey can be modeled as a time-varying game, with the predators trying to eat as much prey as possible to optimize their own numbers and prey like-wise trying to maximize their own numbers while avoiding being eaten. At every instant each population observes the behavior and numbers of the other population, potentially with noise, and attempts to modify its own behavior to optimize the overall reward. Assuming that fish change their behavior depending on environment will hopefully lead to more realistic models, which might for instance be able to explain the phenomenon that when a cod appears herring stop eating and try to hide.

Expanding our understanding in this fashion is of huge importance, since we use ecological models as an integral part of our society, applying them to govern fisheries quotas and nature management. With a better understanding of population dynamics governed by the principle of optimal behavior, we might be able to manage our fisheries better and prevent fish stock collapses.



Picture: "Hiding" by Orin Zebest is licensed under CC BY 2.0, from

PhD project

By: Jacob Emil Friis Frølich

Section: Dynamical Systems

Principal supervisor: Uffe Høgsbro Thygesen

Co-supervisor: Ken Haste Andersen

Project title: Behavioral games and emergent population dynamics

Term: 01/07/2019 → 13/10/2022


Uffe Høgsbro Thygesen
Associate Professor
DTU Compute
+45 45 25 30 60


Ken Haste Andersen
Professor, Head of Section
DTU Aqua
+45 35 88 33 99