tail and gets into a stiff stance during the half-hour copulation. Breeding pairs stay together between 5–20 days before they part their separate ways. The gestation period of a white rhino is 16 months. A single calf is born and usually weighs between . Calves are unsteady for their first two to three days of life. When threatened, the baby will run in front of the mother, which is very protective of her calf and will fight for it vigorously. Weaning starts at two months, but the calf may continue suckling for over 12 months. The birth interval for the white rhino is between two and three years. Before giving birth, the mother will chase off her current calf. White rhinos can live to be up to 40–50 years old. Adult white rhinos have no natural predators (other than humans) due to their size, and even young rhinos are rarely attacked or preyed on due to the mother's presence and their tough skin. One exceptional successful attack was perpetrated by a lion pride on a roughly half-grown white rhinoceros, which weighed , and occurred in Mala Mala Game Reserve, South Africa. Distribution The southern white rhino lives in Southern Africa. About 98.5% of white rhinos live in just five countries (South Africa, Namibia, Zimbabwe, Kenya, and Uganda). Almost at the edge of extinction in the early 20th century, the southern subspecies have made a tremendous comeback. In 2001 it was estimated that there were 11,670 white rhinos in the wild with a further 777 in captivity worldwide, making it the most common rhino in the world. By the end of 2007 wild-living southern white rhinos had increased to an estimated 17,480 animals (IUCN 2008). The northern white rhino (Ceratotherium simum cottoni) formerly ranged over parts of northwestern Uganda, southern Chad, southwestern Sudan, the eastern part of Central African Republic, and northeastern Democratic Republic of the Congo (DRC). The last surviving population of wild northern white rhinos are or were in Garamba National Park, Democratic Republic of the Congo (DRC) but in August 2005, ground and aerial surveys conducted under the direction of African Parks Foundation and the African Rhino Specialist Group (ARSG) only found four animals: a solitary adult male and a group of one adult male and two adult females. In June 2008 it was reported that the species may have gone extinct in the wild. Like the black