Males leave their mothers when they are two years old and join the bachelor groups.
However, bachelor groups tend to be very loose and members can leave whenever they want.
Male Kudus live widespread from the group, or in bachelor groups.
The remaining 80% of males and young females form their own large bachelor group to complete the colony.
There isn't a human society I've heard of where bachelor groups like this are anything but outcasts, without power or prestige.
After giving birth, females will join bachelor groups and live the rest of mating season with them.
There they may become solitary or may form into bachelor groups.
They may start out being solitary and or in bachelor groups.
Males who have not established such territories sometimes form small bachelor groups.
Young males must leave their birth group when fully mature, often forming bachelor groups.