  In the classical Lotka-Volterra population models, the interacting species
affect each other's growth rate. We propose an alternative model, in which the
species affect each other through the limitation coefficients, rather then
through the growth rates. This appears to be more realistic: the presence of
foxes is not likely to diminish the fertility of rabbits, but will contribute
to limiting rabbit's population. Both the cases of predation and of competition
are considered, as well as competition in case of periodic coefficients. Our
model becomes linear when one switches to the reciprocals of the variables. In
another direction we use a similar idea to derive a multiplicity result for a
class of periodic equations.
