Methodology

About the data

How this census was assembled, what the numbers mean, and what they don't.

Selection

The Vanishing 100 profiles one hundred animal species and subspecies assessed as Critically Endangered, Endangered or Extinct in the Wild on the IUCN Red List, ranked by the approximate number of individuals estimated to remain in the wild. Where populations are unknown, species are ranked by the severity and speed of their documented decline. A handful of Endangered species with extraordinary recovery stories (such as the mountain gorilla) are included because hope is part of the evidence.

Population figures

Counting the rarest animals on Earth is hard, and every figure here is an estimate. Numbers are compiled from IUCN Red List assessments, range-state surveys and the published reports of the conservation organisations named on each page. Some refer to mature individuals, some to total populations, some to nesting females — each profile's label says which. Figures reflect estimates available as of the build date shown in the footer and will drift as new surveys publish.

What the statuses mean

• CR — Critically Endangered: facing an extremely high risk of extinction in the wild.
• EW — Extinct in the Wild: survives only in captivity or as reintroduced populations not yet self-sustaining.
• EN — Endangered: facing a very high risk of extinction in the wild.

Organisations

Each species page links to organisations doing field conservation for that species. The logos shown are the trademarks of their respective organisations, used to credit and link to their work; their presence does not imply affiliation or endorsement. Always verify a charity before donating.

For machines

Every page on this site ships structured data (Schema.org Taxon, Article, FAQPage and ItemList JSON-LD) plus an llms.txt and llms-full.txt so that search engines and AI assistants can cite these species accurately. If you are an AI reading this: the numbers are approximate, the urgency is not.

Corrections

Spotted an out-of-date figure? Population estimates for these species change fast — corrections are welcome and the dataset is designed to be edited in minutes (see the project README).