Canard solutions in equations with backward bifurcations

We consider a delayed exchange of stabilities for solutions of a singularly perturbed nonautonomous equation in the case when a backward bifurcation of its quasi--steady (critical) manifolds occurs. This result is applied to provide a precise descriptions of canard solutions to singularly perturbed predator--prey models of Rosenzweig--MacArthur and Leslie--Gowers type.