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Quiz yourself on Ecosystems CommunitiesGet your flashcardsBuild my revision planTrack my progress🔄 Predator-Prey Cycles
In a stable community, the populations of predators and prey rise and fall in repeating cycles:
- Prey population increases — plenty of food, few predators
- Predator population increases — more prey available to eat
- Prey population decreases — more predators hunting them
- Predator population decreases — less food available (prey numbers are low)
- Cycle repeats — with fewer predators, prey numbers recover, and the cycle starts again
The Time Lag
The predator population always peaks AFTER the prey population — there is a time lag because it takes time for predators to breed when food is plentiful, and time for them to die off when food becomes scarce.
Reading the Graph
On a predator-prey graph, the two lines oscillate (go up and down) together, but the predator line is always slightly behind the prey line. The prey line peaks first, then the predator line peaks shortly after.
Exam skill: When describing a predator-prey graph, always mention: (1) both populations oscillate, (2) predator peaks AFTER prey, (3) explain WHY using the food availability link.
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