The population density and spatial distribution of animals vary regularly by corresponding population mechanisms. The growth of population density in most species is accompanied by their discharge into the environment of metabolic products, including special signaling substances that inhibit or accelerate growth and development, limit or even arrest reproduction, increase mobility, and change behavior. As a result, with high population density, resettlement is intensified and mass emigration may begin. When population density decreases, emigration is curtailed and mobility somewhat decreases, increasing anew when the population becomes very sparse and threatens intra-population groupings (families, flocks, herds, colonies) with destruction. Intensity of reproduction is simultaneously increased