Practice question

Predator abundance depends on energy and nutrients obtained from prey. When prey decline, predators encounter food less often, reducing intake, body condition, survival, and reproductive output. Starvation and emigration can cause an immediate decrease, while reduced recruitment creates a delayed response. This lag is why predator peaks often follow prey peaks in coupled population cycles. High prey abundance ordinarily supports predator growth rather than decline, and an increased predator reproductive rate would raise population size unless outweighed by mortality. Lack of competition may relieve a constraint but cannot compensate indefinitely for insufficient food. In the Lotka–Volterra model, predator change is dP/dt = baNP − mP = P(baN − m); below the prey threshold N = m/(ba), predator mortality m exceeds gains from consuming prey and predator numbers fall. Alternative prey, stored reserves, or immigration can weaken this relationship in nature, but the mechanistic expectation remains a predator decline when its effective resource base falls below replacement needs.