The white rhinoceros, white rhino, or square-lipped rhinoceros (Ceratotherium simum) is the largest extant species of rhinoceros. It has a wide mouth used for grazing and is the most social of all rhino species. The white rhinoceros consists of two subspecies: the southern white rhinoceros, with an estimated 19,682–21,077 wild-living animals in the year 2015, and the much rarer northern white rhinoceros. The northern subspecies has very few remaining individuals, with only two confirmed left in 2018 (two females: Fatu, 18, and Najin, 29), both in captivity. Sudan, the world’s last known male Northern white rhinoceros, died in Kenya on 19 March 2018 at age 45.