Impala have a complex social structure and an interesting mating system. Like other antlered ungulates, impala mate during a certain period of time called the rut. During this period, the adult males, which normally live in bachelor herds, become territorial (2). Physical changes also occur in the males during this time; their necks thicken, their coats become darker from the grease of sebaceous secretions and they acquire a musky scent (4). The males fight for territories to attract females with which to mate, and their roars and snorts can be heard day and night (2). After the rut, the male's territoriality and fighting urge wanes, and they regroup into bachelor herds or join breeding herds (2). A brief resurgence of this activity in some of the males occurs again in a secondary rut later in the year (2). Female impala and their young live in breeding herds (2). The majority of young are conceived in the first rut and are born after a gestation period of 194 to 200 days (2). Females give birth to a single young in a secluded spot, remaining nearby and returning frequently to suckle their young (4). After a few days the young will begin to follow the mother, a time when they are particularly vulnerable to predators; about half the young are lost to predation within the first few weeks (4). Young males are evicted from breeding herds by territorial males and remain in bachelor herds until they are old enough to establish a territory (2). Impala can live for around 15 years (4). Impala have a varied diet compared to closely related species. During the wet season, they mostly graze on grass, and as this dries they browse more on shrubs and bushes (2) (7). Impala also consume fruits and Acacia pods when available (2). This varied diet means that impala can obtain relatively high quality food throughout the year in a small home range, without undertaking massive migrations as many African mammals do (7).