Here f(N) captures any change in the prey population not due to predator activity including inherent birth and death rates.
Predators receive a reproductive payoff, e, for consuming prey, and die at rate u.
[1] The merit of ratio-dependent versus prey-dependent models of predation has been the subject of much controversy, especially between the biologists Lev R. Ginzburg and Peter A.
[3] A later review critically examines the claims made about ratio-dependent predation to find that the added value of the ratio-dependent predation models is unclear and concludes that "As empirical evidence is often lacking on both functional responses and the importance of functional responses for population dynamics, there is no need to strongly favor one limit model over the others."
[4] A recent ecology undergraduate textbook devotes about equal space to Lotka-Volterra and Arditi-Ginzburg equations.
[5] Neither prey-dependent nor ratio-dependent models can claim universal accuracy but the issue is to identify which is least wrong.