Thousands of species worldwide are at risk of suffering the same fate as the dodo bird, to name one famously extinct species. The International Union for the Conservation of Nature maintains a “Red List” of at-risk species. Certain animals are classified as either “Extinct” or “Extinct in the Wild” (animals found only in captivity), but the next most serious category is “Critically Endangered,” for animals whose populations have decreased by 80 percent in the past three generations.