Lions are the only big cats to live in family units called prides. Other big cats live solitary lives, except when breeding or raising cubs. A lion pride may include up to three males, a dozen females, and their young. All of a pride's female lionesses and cubs are typically related. At around two to three years old, young males leave the pride and attempt to take over another male's pride. The social structure of the pride is based on specific roles. Lionesses are the primary hunters, while dominant males are responsible for protecting the pride's territory. Lion prey includes antelopes, zebras, wildebeest, buffalo, and other grassland animals. These animals are often larger and faster than an individual lion. By hunting together, lions are able to exhaust and kill their prey.