The Red Data Book is a catalogue compiled by the International Union for Conservation of Nature (IUCN) which lists species that are at risk of extinction. It uses a set of criteria to evaluate the extinction risk of thousands of species and subspecies. The categories included range from Extinct, Extinct in the Wild, Critically Endangered, Endangered, Vulnerable, Near Threatened, Least Concern, to Data Deficient and Not Evaluated. While it includes more than just 'Endangered' species, 'Endangered' is the core category it primarily focuses on highlighting, alongside other threatened categories like Critically Endangered and Vulnerable.