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Why do hare and lynx numbers boom and crash again and again?
Predator-Prey Dynamics lab · Last updated: 16 October 2026
Why do hare and lynx numbers boom and crash again and again? In this 3D lab, you watch prey multiply, predators feast and both populations rise and fall in turn. It shows how two species can control each other's numbers, and why the predator peak always arrives a little after the prey peak.
What you'll discover
- When prey is plentiful, predators have plenty of food, so their numbers rise.
- Rising predator numbers cut the prey population, and then the hungry predators decline too.
- The two populations cycle, with the predator peak lagging behind the prey peak.
The science in plain words
Predators and their prey are linked in a feedback loop. When prey such as snowshoe hares are plentiful, predators such as lynx find food easily, raise more young and increase in number. More predators eat more prey, so the prey population falls. With less to eat, predators then struggle and decline. With fewer predators about, the prey recover, and the cycle starts again.
A famous real example comes from fur-trading records kept in Canada over many decades. They show snowshoe hare and lynx numbers rising and falling roughly every ten years, with lynx peaks following soon after hare peaks. Later studies found that the hares' food supply and other predators also play a part, so real cycles involve more than two species.
Mathematicians described this pattern in the 1920s with a pair of equations now called the Lotka-Volterra model. Its predictions show the same repeating rise and fall, with the predator curve shifted slightly behind the prey curve because predators take time to respond. Understanding these cycles helps scientists manage wildlife, fisheries and pests, and shows why removing a predator can let prey populations explode and damage their habitat.
Where it fits
- India, NCERT: Population cycles go beyond the NCERT syllabus for classes 6 to 10; the lab builds on food chains in Class 10 Our Environment.
- United States: Grades 6 to 12
- Next Generation Science Standards: MS-LS2-1, MS-LS2-2, HS-LS2-1
Common questions
Why do predator and prey populations go up and down?
They depend on each other. Plenty of prey lets predators increase, but more predators eat more prey, so prey numbers fall. Then predators run short of food and decline, which lets the prey recover. This feedback produces repeating cycles.
Why does the predator peak come after the prey peak?
Predators need time to respond. After prey becomes plentiful, it takes a breeding season or more for extra predator young to be born and grow up. By the time predator numbers peak, they have already started to reduce the prey population.
What would happen if all the predators disappeared?
Without predators, the prey population would grow quickly until it ran short of food. The prey could then overgraze their habitat, starve and crash. Predators help keep prey numbers in balance with the plants they eat.
Related labs
- Population Dynamics: One plant becomes two, two become four… Can a population keep doubling for ever?
- Food Web: Who eats whom in a meadow? Take one species away and see what happens to the rest.
- Natural Selection: Why do living things fit where they live so well? Watch hungry birds change a moth population.
See all biology labs or every Taz science lab.
Try it yourself
The Predator-Prey Dynamics lab is one of the interactive 3D science labs inside Taz. Change one thing, predict what will happen, then run it and watch. Labs open after you sign in.