Questions: Predator-Prey Dynamics and the Lotka-Volterra Model

Question 1

In the Lotka-Volterra predator-prey model, what is the relationship between the timing of predator and prey population peaks?

• A. They peak simultaneously
• B. The predator peak leads the prey peak
• C. The predator peak lags behind the prey peak
• D. There is no consistent relationship between the two peaks

Answer: (C)

Predator populations grow in response to abundant prey, so the predator peak follows the prey peak with a time lag. When prey is abundant, predators reproduce more; the growing predator population then depletes prey; as prey crashes, predators decline due to food shortage. This phase lag is a diagnostic feature of the Lotka-Volterra cycle and is visible in empirical data like the lynx-snowshoe hare records.

Question 2

The basic Lotka-Volterra model predicts that predator and prey populations will eventually reach a stable equilibrium where both populations stop changing.

• T. True
• F. False

Answer: False

The Lotka-Volterra model predicts neutrally stable cycles — the populations oscillate indefinitely around an equilibrium point rather than converging to it. The equilibrium exists mathematically, but it is unstable: any small perturbation sends the system into oscillations. A stable equilibrium (where perturbations damp out) requires added complexity such as prey self-limitation or predator saturation.

Question 3

Why does overhunting by predators ultimately harm the predator population itself, and how does this create the oscillating cycle?

Model answer: When predators are numerous, they consume prey faster than prey can reproduce, crashing the prey population. With prey scarce, predators starve and their numbers decline. As predator pressure drops, prey recovers, which then allows predators to increase again — repeating the cycle.

This tests understanding of the feedback mechanism rather than just recalling that cycles exist. The key is that predator success today depletes the resource (prey) that predator success tomorrow depends on — a time-delayed negative feedback that generates oscillations.