Two models for competition between age classes

We consider two lumped age-structured models of juvenile against adult comp etition, one of which is a compartmental ordinary differential equation (OD E) model and one of which is a system of ODEs with delay derived from the M cKendrick partial differential equation (PDE) model. Existence and stabilit y of positive equilibria and existence of oscillatory solutions of both mod els are studied. Using a competition parameter, which measures the intra-sp ecific competition, we investigate the effects of the competitive interacti ons between juveniles and adults on the dynamics of the population for both models. We find that these effects are different for the two models and di scuss the differences from the modeling perspective. The discussion reveals an interesting relation between the length of the maturation period and th e vital rates' dependence on the competition parameter. (C) 1999 Published by Elsevier Science Inc. All rights reserved.