Finding a Mate

For a population to survive, individuals must find a mate and reproduce. The ability to find a mate is therefore a biotic factor that affects population size, especially in species that live at low density.Low population density. If a population becomes very small or spread out, individuals may rarely meet a suitable mate. The birth rate falls, so the population may decline further even if food and habitat are plentiful. This is a particular danger for endangered species, where the last few individuals may be scattered over a large area. A small population also has low genetic diversity, and mating between relatives (inbreeding) becomes more common, which can reduce fertility and survival.Competition for mates. At high density, members of the same sex compete for mates. This is intraspecific competition. Only some individuals, often the strongest or most attractive, get to breed. Examples include red deer stags fighting with their antlers during the rut, and male birds of paradise performing elaborate displays.Courtship behaviour helps animals find and choose a mate. It allows individuals to recognise members of their own species, so they do not waste energy on matings that cannot produce fertile offspring, to find a mate that is sexually mature and ready to breed, and to choose a strong, healthy partner. Signals may be visual (colours and displays), sounds (bird song, frog calls) or chemical, such as pheromones released by female moths, which males detect over long distances.Many animals also need a territory before they can attract a mate, covered in the next lesson.