Predator and prey simulation

What this simulation shows

Predators and their prey affect each other's numbers. When there are lots of rabbits, foxes find food easily and raise more young, so the fox population grows. More foxes eat more rabbits, so rabbits decline. With fewer rabbits, foxes go hungry and their numbers fall, which lets the rabbits recover. The result is a repeating cycle, with fox peaks coming after rabbit peaks. This simulation uses a simple mathematical model of these rules, based on the Lotka–Volterra equations. Four settings change rabbit births, fox hunting success, fox deaths and the amount of grass, which limits how many rabbits the land can support.

Why a simulation helps

Population cycles take years in nature, so students can't watch them happen. A model can run 10 years in a few seconds and be run again with one thing changed. That lets students ask "what if?" questions and test their predictions, which is the heart of science. It also shows the limits of models: real ecosystems have weather, disease and many more species.

Common misconceptions

• Predators do not usually wipe out their prey. Prey numbers fall, but they recover once the predators go hungry.
• Better hunting is not always good for predators. If foxes catch too many rabbits, the rabbits crash and the foxes starve.
• The two populations do not peak together. Prey usually peak first, and predators follow.
• A graph from a model is not real data. Models simplify nature, so their numbers are predictions to test, not facts.

A 10-minute ecology activity

• Ask the student to sketch what they think a graph of rabbits and foxes over time will look like.
• Run the simulation and compare its shape with the sketch.
• Change one setting at a time, predicting before each run.
• Try to reach both goals: keep both alive for 10 years, and make the foxes die out.
• Discuss the famous fur-trade records of snowshoe hares and lynx in Canada, whose numbers rose and fell in cycles of about ten years.

Where this fits in school

• US, grades 6 to 8: NGSS MS-LS2-1 asks students to analyze data on how resource availability affects populations, and MS-LS2-2 looks at patterns of interaction such as predation.
• US, high school: NGSS HS-LS2-1 asks students to use mathematical representations to explain factors that affect carrying capacity.
• England, Key Stage 3: students study the interdependence of organisms in an ecosystem, including food webs.
• England, GCSE Biology: students interpret graphs of predator and prey populations rising and falling in cycles.

Learning more

Science is part of Eurekami's skill map, with lessons that draw science diagrams live and narrate them in English or Spanish. When a question is tricky, the AI tutor asks guiding questions so the student does the reasoning. For older students, Exam Prep includes GCSE Combined Science practice papers.