21 Lotka-Volterra predator-prey dynamics
21.1 Background
The Lotka-Volterra predator-prey model (Rosenzweig and MacArthur 1963) is a fundamental concept in ecological dynamics, used to study the dynamics between predator and prey populations. The model assumes that the predator’s population growth is directly influenced by the availability of its prey, while the prey’s population growth is affected by predation pressure. As predator numbers increase, the prey population declines, which, in turn, leads to a decrease in predator numbers due to reduced food availability. This cyclical pattern continues as predator and prey populations oscillate over time.
The Lotka-Volterra predator-prey model gives us a framework for understanding the dynamics of species interactions.
In this class you will build and explore a Lotka-Volterra predator-prey model in Excel to gain insight into the ecology of interacting predators and prey.
Learning outcomes:
- Competence in constructing an Excel-based population model.
- Understanding how the Lotka-Volterra predator-prey model works, and how it is visualised.
21.2 Your task
Follow the PDF worksheet (here), which guides you to build and explore a Lotka-Volterra predator-prey model in Excel. The model has parameters for the prey and for the predator, and you will explore how these parameters influence the dynamics of the populations.
The worksheet is divided into three parts. We will mainly focus on Part 1 - the basic model - in the class.
After completing the Excel sheet, try to answer the following questions:
- Does a larger prey population growth rate (R) increase or decrease the stability of the predator-prey interaction?
- What happens if the predators starve more quickly? Less quickly?
- What happens if the predator is more efficient at converting prey into offspring? Less efficient?
- What happens if the predator is better at finding prey? Worse?
- Is the behavior of the model sensitive to starting populations? Begin with populations near the point where the isoclines cross, and move slowly farther out.
- What is the ultimate outcome of the predator-prey interaction, regardless of parameter values? How does this compare to real predator and prey populations? What factors not included in the model may explain the differences between model predictions and reality?