The word 'rare' is often associated with something limited, unique, and distinctive, such as rare gems, jewels, antique items, and various collectibles. However, being rare also means that once something is gone, it's gone forever. In the animal world, rare also stands for endangered, which is exactly what the rarest animals are. According to WWF's recent report, since 1970, wildlife populations worldwide have decreased by an average of 69%. Pollution, global warming, deforestation, and other outcomes of globalization, as well as poaching, are some of the leading causes putting rare animal species on the verge of extinction. And unfortunately, destruction is often easier than recovery. Thus the list of rarest species and endangered animals is unlikely to decrease any time soon. According to the IUCN Red List, more than 42,100 species are threatened with extinction. Most of those threatened belong to the animal kingdom, making them some of the rarest animals in the world...