Formalization of the basic concepts of animal ecology

Summary Formal definitions of the following concepts of animal ecology are given: environment, niche, locality, local population, natural population, community, ecosystem. Five primitive (undefined) notions are used including animal, offspring and habitat, the latter in the sense of Charles Elton. The defining equations for the environment of one animal are first given, then niche (in the Elton sense) is formally defined in terms of the environment. The fifth primitve notion habitat is then introduced in order to define the remaining concepts.