This is primarily a sub-category forIUCN Red List species by the external threat(s) stated in IUCN reports for each listed species (hyperlinked under 'References' &/or 'External links' on most wikipedia articles when species are on IUCN Red List). Please note that many species are or have been endangered by more than one threat, and may be in several sub-categories.
Non-IUCN Red Listed species may also be categorized, when 'officially' on other international conservation organization &/or government agency lists. As such lists are often updated slowly, newly-discovered species and threats reliably reported in the academic literature may also be acceptable (these should be discussed and cited in the article).
