The white rhinoceros 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 had very few remaining, with only 3 confirmed individuals left in 2015 (2 females: Fatu, age 15, and Najin, age 25; and 1 male: Sudan, age 42), all in captivity.