A breeding population consists of a group of members of a species that produce offspring by breeding.The population should be large enough to maintain itself. Without an adequate number of members in the group the reproductive viability is reduced to the point where the population will eventually disappear, owing to more deaths than births.

As an example, a breeding population of cockroaches can consist of only two members: one male and one female. There's no doubt the population will perpetuate itself. However it is doubtful that one male and one female elephant, although they mate, would be considered a breeding population.