A number of other hypotheses exist. One such is that philopatry is a method, in migratory species, of ensuring that the sexes interact in breeding areas, and that breeding actually occurs. A second is that philopatry provides a much higher chance of breeding success. Strict habitat requirements – whether due to a precisely adapted genome or not – mean that individuals that return to a site are more familiar with it, and may have more success in either defending it, or locating mates. This hypothesis does not justify whether philopatry is due to an innate behaviour in each individual, or to learning; however it has been shown that, in most species, older individuals show higher site fidelity. Neither of these hypotheses is as widely accepted as the optimal-inbreeding or dispersal hypotheses, but their existence indicates that the evolutionary causes of natal philopatry have still not been conclusively demonstrated.