  In the context of Mass Varying Neutrinos(MaVaNs) we study a model in which a
scalar field is coupled to more than one species of neutrinos with different
masses. In general, adiabatic models of non-relativistic MaVaNs are heavily
constrained by their stability towards the formation of neutrino nuggets. These
constraints also apply to models with more than one neutrino species, and we
find that using the lightest neutrino, which is still relativistic, as an
explanation for dark energy does not work because of a feedback mechanism from
the heavier neutrinos.
