A range of mathematical models have been developed by relaxing the assumptions made in the Lotka-Volterra model; these variously allow animals to have geographic distributions, or to migrate; to have ...A range of mathematical models have been developed by relaxing the assumptions made in the Lotka-Volterra model; these variously allow animals to have geographic distributions, or to migrate; to have differences between individuals, such as sexes and an age structure, so that only some individuals reproduce; to live in a varying environment, such as with changing seasons (Cushing, 2005; Thieme, 2003); and analyzing the interactions of more than just two species at once.