Introduction:

This simulation models the dynamics between plants, prey (herbivores) and predators (carnivores). When animals feed, their internal energy meters (shown as internal shapes) fill up, enabling reproduction when they are full. As animals move, metabolism depletes their energy meters; when it reaches zero, the animal dies. Once eaten, plants regenerate after a set period of time. You can adjust various starting conditions and see the effect they have on the overall system.

Controls:

• Click ‘Start/Pause/Resume’ to run the simulation, and ‘Reset’ to return to the initial conditions set by the sliders.
• Toggle ‘Display graph’ to show or hide a graph tracking the numbers of each organism. You can toggle each line on or off using the checkboxes in the key. Dragging the graph left-right will show earlier data if the time has gone over 120 seconds.
• Toggle ‘Failsafe’ on to prevent the last predator or prey from being eaten/dying. This guarantees cyclical behaviour emerges, but is unrealistic.
• Toggle ‘Reproduction mode’ to ‘Instant’ to make animals reproduce as soon as their energy meters fill up (less realistic) or ‘Probabilistic’ to give a per-second chance of reproduction when their energy meters are full.
• Toggle ‘Energy flow’ to ‘Fixed’, meaning predators gain a fixed amount of energy when they feed, and ‘Variable’ where predators gain as much energy as the prey currently have when they feed.
• Choose settings presets from the drop-down to view particular behaviours more effectively.
• Click the ‘speed multiplier’ buttons to speed up the simulation (note, this tends to exaggerate behaviour).

Settings:

Adjust the sliders to change various settings:

• ‘Initial population’ (predator and prey only)
• ‘Energy content’ (predators, prey and plants) – determines the energy content of each organism, and how much energy they need to reproduce.
• ‘Movement speed’ (predators and prey only)
• ‘Metabolic rate’ (predators and prey only) – determines how quickly animals use their energy supply.
• ‘Decision frequency’ (predators and prey) – determines how regularly animals change direction to move towards food and away from predators.
• ‘Reproductive cooldown’ (predators and prey) – determines the interval between reproductive events (can prevent/trigger population explosions).
• ‘Regeneration time’ (plants only) – determines how long plants take to regenerate after being eaten.