The Big Five occur in many of the game and nature reserves in Limpopo. Buffalo are the most abundant of the Big Five and occur in large herds that can number up to 600 animals. Deceptively docile, these animals are powerful and aggressive - particularly old bulls ejected from the herd who form small bachelor herds. When alarmed, a herd also tends to stampede. Buffalo are regularly preyed upon by lions. Elephants live in tightly-knit family groups led by a matriarch. The bulls remain solitary or may band together to form bachelor herds. A fully-grown elephant weighs around 6 000 to 7 000 kilogram and is the largest terrestrial animal. When there are young in the herd, the adult female may become aggressive and it is advisable not to venture too close to the herd. The leopard is a shy nocturnal animal that hunts mainly at night. This, and the fact that it prefers dense riverine areas and craggy hills, explains why it is often not easily spotted. The leopard hides its prey in trees from other predators and is often seen resting on a branch in a tree. It is the most wary and stealthy of the big cats, yet can be incredibly bold. Lions are the largest of the African cats and live in prides of varying size controlled by one or more dominant males. An adult male weighs about 180 kilograms and a female, 135 kilograms. Lions live for up to 20 years. The lion's roar, normally heard at dawn and dusk, can easily be heard within a radius of many kilometres. The rhinoceros is classified as either white or black, although there is no real colour difference between the two species. White rhino are generally larger with a flattened or square mouth and feed on grass. Black rhino have a pointed mouth that they use to strip leaves and break twigs. Rhino weigh up to 1 500 kilogram. The rhino's horn is formed from matted hair and skin.