The Na'vi are monogamous creatures who mate for life. The mechanics of reproduction are similar to that of humans and other Terran mammals. However, their unique physiology provides the Na'vi with a level of intimacy unknown on Earth. Cultural anthropologists believe that when an appropriate mate has been selected (which can take many years), the male and female Na'vi will connect queues in an act called tsaheylu to create an emotional bond that lasts a lifetime. The intertwining of queues is both highly erotic and profoundly spiritual, but is not the actual act of sexual reproduction. The tsaheylu bond between Na'vi during mating should not be confused with the non-erotic tsaheylu bonds Na'vi make with animals and plants, like the "mental reining" that Na'vi use to control animals or the use of the queue to access the Pandoran Neural Network.
Traditionally, once a Na'vi male has passed the tests on the path to manhood and has been accepted into the clan as an adult, he is not only allowed to make his bow from the wood of the Hometree, but he is also expected to choose his woman. After the woman has been chosen, the new couple are mated before Eywa. Jake Sully chooses Neytiri to become his mate, and she accepts and mates with him under the Tree of Voices following his acceptance into the Omaticaya clan as 'One of the People'.
Once tsaheylu is made between the couple, the ultimate in intimacy, pleasure that is unfathomable to humans, causes the somewhat unwillful sharing of the couple's good memories, and is a sign of Eywa's acceptance. If a couple can be foreseen to not have a pleasant or happy future, Eywa has been known to reverse the feeling produced by making tsaheylu, a sign to the couple that mating would only, in simple words, ruin their lives together, and therefore prevents the mating, because of its lifelong span. After the resulting embracing and kissing, the couple is sent to sleep by Eywa, and the two dream hintings of their future together. The couple will experience the pleasure of tsaheylu from the moment of connection, until they awaken and have completed mating, and when they disconnect and return to their clan, they are mated for life.
A Na’vi female will typically produce from one to ten offspring, often spaced widely apart in time. Na’vi females have two breasts, and nurse their infants for up to four months. Some Na’vi elect to abstain from reproduction, despite being sexually active. It is not known how contraception is accomplished in this case, although the Na’vi appear to be quite sophisticated in this regard. Sexual activity outside of the bonded pair is not uncommon, but is almost always associated with fertility rituals and other rites, and has never been reported to lead to a disruption of the pair bond. Na’vi males are typically pair bonded with females, but male-male and female-female permanent bonds are not uncommon.