Mating and breeding occurs throughout the year. The dominant silverback mates with all females in the group as soon as they begin ovulation. The moment when a female gorilla is ready to mate is not evident physically like it is in chimpanzees. In most cases, it is the female who initiates the mating process as soon as she ready. When a female gorilla is ready to mate, she will approach the dominant male slowly, make sustained eye contact and purse her lips. Should the male not respond, she will attract his attention by slapping the ground as she reaches towards him. If the dominant male is too busy or doesn’t react after several attempts, she may be open to mating with other males in the group.

The dominant silverback can also initiate mating by approaching the female and touching her or making a display with a grunt. If the female is hesitant or resistant, the silverback may charge and slap the female to give in. A study in 1982 found that a silverback’s aggression towards a particular female forced her to initiate the process of mating even when she wasn’t in estrus. Actual mating occurs on the ground with the silverback on top of the smaller female. The female appears to kneel down as the female completes the copulation process. It was thought that face to face sex was unique to bonobos and humans but some gorilla species (mountain and western lowland gorillas) have been observed having sex with the individuals looking directly at each other.

Sex for competition and for leisure is also not unheard of in gorillas. Female gorillas frequently use sex to gain the favor of the dominant silverback to stop him from mating with other females. There have even been cases of pregnant females mating with the silverback to reduce the chances of other fertile females from conceiving. The attention given to a fertile/ovulating female by the silverback tends to arouse competition among females in the group. In all gorilla subspecies, the dominant silverback prefers mating with older experienced mothers. Generally, western gorilla males tend to mate with every female in the group regardless of whether they are fertile or not. Mountain gorilla silverbacks prefer to mate only with a fertile female.

It is important to note that although silverbacks form strong and long lasting social bonds with females in his group, they will start leaving him for another group when he gets too old or is at the end of  his reproductive years. A few will remain loyal to the dominant silverback but will join another group in case he dies. Females have been observed changing groups several times during their lifetime. They do this to protect their future offspring. If the dominant silverback dies before weaning, the infant will be killed by the male taking over.