NetLogo Wolf Sheep Predation model
Introduction
This short article summarized some technical and conceptual hightlights from Wilensky et al. Wolf Sheep Grass predation models created in NetLogo.[1]
NetLogo is a tool for agent-based modelling and simulation, which is part of what can be called computational thinking. Wilensky and Reisman [2] [3] make an interesting case for learning biology through constructing and testing such computational models.
The agent-based version is also discussed in Population dynamics between preys and predators by Moira Zellner and Pierre Bommel and they also present an oscillating version where the wolf/sheep proportion is lower.
The Netlogo libray wolf-sheep models
The Wolf Sheep predation model distributed with NetLogo includes two variants:
- A Wolf-sheep model where the wolves (or the sheep) die out
- A Wolf-sheep-grass model that is oscillating stably over time
The model can be found in NetLogo desktop software like this:
- File -> Models library (CTRL-M)
- Sample Models -> Biology -> Wolf Sheep Predation
You can try running this simulation directly in your web browser. It worked well enough in Firefox/Ubuntu 10 and Firefox/Win10. Both machines did have a good graphics cards. The online version also allows editing the code, i.e. make changes to the inner workings of the model.
A simple wolf - sheep model
Example run: Toward a desaster.
We ran the model with the default parameters. A model without grass is unstable over time. Since it includes probablistic functions, the same model using the same parameters can evolve bit differently over time. After a few hundred ticks the world is usually in a bad state and also will take a lot of CPU. E.g. in one run I had 180K sheep, 3600 wolves and no grass after 450 ticks. The wolves then grew > 100K and eat all the sheep. After 775 ticks, only grass was left.
The wolf - sheep - grass model
This model leads to a stable solution as you can see in the picture below. After 4500 ticks, both sheep and wolves are still around.
Bibliography
- ↑ Wilensky, U. (1997). NetLogo Wolf Sheep Predation model. http://ccl.northwestern.edu/netlogo/models/WolfSheepPredation. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.
- ↑ Wilensky, U. & Reisman, K. (1998). Connected Science: Learning Biology through Constructing and Testing Computational Theories – an Embodied Modeling Approach. International Journal of Complex Systems, M. 234, pp. 1 - 12.
- ↑ Wilensky, U. & Reisman, K. (2006). Thinking like a Wolf, a Sheep or a Firefly: Learning Biology through Constructing and Testing Computational Theories – an Embodied Modeling Approach. Cognition & Instruction, 24(2), pp. 171-209. http://ccl.northwestern.edu/papers/wolfsheep.pdf