American bison

Nearly every bison alive carries a little cattle in it. The survivors of the slaughter were mostly held by ranchers who crossed them with cattle deliberately, and when a 2022 genomic survey went looking, every herd it tested turned up traces, Yellowstone included.

The introgression is real but small. Levels ran from about 0.24 percent of the genome in one Yellowstone animal to 2.45 percent in a wood bison specimen from 1937. No sample in the study came back clean, which retired the long-standing belief that a few parks held pure herds.

Near Threatened, with half a million animals alive. The Red List counts only the conservation herds, not the commercial bison raised as livestock, and those herds are small, fenced and managed rather than a wild population running loose on the plains.

There are two kinds. Plains bison and the larger, higher-shouldered wood bison of the northern forests are both covered by the same species assessment, and both were down to a few hundred animals at the low point.

The bones were the last business. After the herds were gone, the skeletons left on the plains were collected by the wagonload and shipped east to be ground for fertiliser and bone char, which is why the photographs of that period are mostly of skull piles.