Black-footed ferret

This is the clearest case of a genetic bottleneck on the list. Conservationists caught the last 18 wild black-footed ferrets between 1985 and 1987 before disease could finish them, and only seven of those became founders. Every ferret alive today is, in effect, a sibling or first cousin of every other. Captive breeding has since returned thousands of ferrets to the prairie, yet the wild population is still only a few hundred. Sylvatic plague kills every unvaccinated ferret it reaches, so wild animals depend on vaccination. To widen the gene pool, scientists cloned Willa, a ferret who lived in the 1980s, from tissue frozen ever since; her clone Elizabeth Ann was born in 2020, and clones made in 2023 have since produced kits of their own.