Day
Rabbits · Foxes
- Grass
- Rabbits
- Foxes
Both living
Tap drops
Equations mode draws the Lotka-Volterra maths as dashed lines, starting from today's numbers, so you can compare.
How to play
- Press Play. Rabbits eat the grass and multiply. Foxes chase the rabbits.
- Watch the chart: rabbits boom, then foxes boom, then rabbits crash, then foxes crash. Again and again.
- Try the three presets, then the sliders. Turn on Equations mode to compare with the maths.
| Do this | Phone | Keyboard |
|---|---|---|
| Drop rabbits / foxes | Pick one, tap the field | R / F (random spot) |
| Play / Pause | Play button | P |
| New run | Button | N |
| Speed 1× / 2× / 4× | Button | S |
| Equations mode | The toggle | E |
| Presets | Buttons | 1 2 3 |
| Sliders | Drag | Tab + arrows |
What's happening?
- Lots of grass means lots of fed rabbits, so rabbits boom.
- Lots of rabbits means easy meals, so foxes boom, a little later.
- Now foxes eat rabbits faster than they're born. Rabbits crash.
- No rabbits, no food: foxes hit their hunger limit and starve. Foxes crash. The grass grows back, and it starts again.
- The rabbits-vs-foxes plot turns those waves into a loop. Each trip round is one cycle.
- Equations mode shows the Lotka-Volterra equations (1920s). They have no grass, no space and no bad luck, so their loop never dies out. Real animals can.
Try this: start from Everything crashes. Can you change just one slider so rabbits and foxes live together for 1,000 days? Which slider did it, and why does it help?