Red Listed: Study Finds One-Fifth of World's Vertebrates Are at Risk

Hawaiian monk seal comes ashore
John Johnson/Marine Photobank

A 2010 study of IUCN's Red List of Threatened Species found that one-fifth of the world's vertebrates (animals with backbones) are threatened with extinction, including this Hawaiian monk seal. The Hawaiian monk seal (Monachus schauinslandi) is the one of the rarest marine mammals in the world: there are around 1,200 individuals alive today, around 1/3 the population size compared to 1950. Its threats include lack of food, as it competes with fisheries for some of the same prey species, and entanglement in fishing lines and other marine debris. See a slideshow of some of the rarest marine vertebrates and watch a video about Hawaiian monk seals on