Within one species, taxonomists differentiate distinct subspecies, characterized by a third name and a detailed taxonomic description. For example, within the gorillas, scientists distinguish between the mountain gorilla – Gorilla gorilla beringei Matschie 1903, the Eastern flatland or Grauer´s gorilla – Gorilla gorilla graueri Matschie 1914. The so-called nominate species Gorilla gorilla gorilla (Savage & Wyman, 1847) was originally described by the american naturalists Savage and Wyman, while the two subspecies were described later by Paul Matschie (1861-1926). If no subspecies are known, the species is monotypic, indicated by mono in the GROMS database.
Populations are often differentiated by conservationists, indicating distinctly distributed or behaving subunits, sometimes of ill-defined or disputed taxonomic status. In GROMS, we are using the names used by conservationists, mostly based on the geographic distribution, as for example the distinct populations of the Northern pintail (Anas acuta), a widely distributed monotypic duck with populations in North America, Northeastern Europe and Asia.Especially within migratory species, different subspecies and/or populations are characterized by distinct migration behaviour, which is illustrated by the animated map of migration routes of the sandhill crane.