Gorillas achieve sexual maturity at the early ages of 10 to 12 years old, while males mature at 11 to13 years. With no designated mating season, they are free to mate year-round, but females are in heat during one or two days monthly. Before mating, females must leave their troop in search of a “silverback” male from another group. During mating, the silverback leader gets nearer to touch her and emits sounds. Often when groups of males assemble, they copulate on the ground with the females being forced to mate with multiple male Gorillas.