This is a model of a simple predator-prey ecosystem. It uses the System Dynamics Modeler to implement the Lotka-Volterra equations.
The Lotka-Volterra equations are a pair of first order, non-linear, differential equations that describe the dynamics of biological systems in which two species interact.
At each step, the value of the SHEEP-BIRTHS flow is added to SHEEP stock, and the value of the SHEEP-DEATHS flow is subtracted from the SHEEP stock. The same is done for the WOLVES stock. Each flow is calculated in terms of the variables, and stocks that are linked to it.
View the SHEEP and WOLVES monitors for the current value of those populations.
View the plot to observe the populations changing over time.
What happens when the sheep population increases? And the wolves? Why do you think this is the case?
Use the System Dynamics Modeler to change the values of the variables in the system, such as SHEEP-BIRTH-RATE and PREDATOR-EFFICIENCY.
This model uses the System Dynamics Modeler to simulate the Lotka-Volterra equations.
Lotka, A.J. (1956). Elements of Mathematical Biology. New York: Dover.
Wilensky, U. (2005). NetLogo Wolf Sheep Predation (System Dynamics) model. http://ccl.northwestern.edu/netlogo/models/WolfSheepPredation(SystemDynamics). Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.