In many ecological systems, when the population drops below a certain level, it cannot support itself anymore. For example this happens when mates cannot be found, lack of cooperation, being too exposed to predators, etc. This effect is commonly referred to as the Allee Effect. A simple model for the Allee effect can be cast in the following form: dP dt = g(P) where g(P) = −a P (P − Pm)(P − M), (3) where a > 0 is a constant [related to r in Eq. (2)], M is the carrying capacity as before, and Pm is another special population size such that Pm < M (as depicted in the plot).