In 1944 the Coast Guard put 29 reindeer on St. Matthew Island in the Bering Sea — deep lichen, and no wolves. By 1963 there were 6,000. Two winters later, 42. The herd had eaten its slow-growing forage faster than it could regrow.
With food to spare, a population grows logistically and levels off at its carrying capacity K. But when growth outruns the forage's recovery, the herd overshoots — and the debt is paid as a crash.
Add a predator and the smooth curve becomes a Lotka–Volterra cycle: prey rise, predators follow, prey fall, predators starve, prey recover. The dashed lines are the nullclines — where each population holds steady; the orbit circles their crossing.
Enrich the island (raise K) and the cycles grow wider, not calmer — the "paradox of enrichment." Push far enough and a trough touches zero: extinction.
Something in the simulation stopped unexpectedly — the lesson continues without it. Nothing you did was wrong; you can move on.