Every morning, gibbons sing to strengthen bonds and mark their territory. These melodious calls are made from sunrise until noon. They last about 11 minutes and can be heard up to 1 km away. Gibbons use vocalizations to communicate between individuals of the same species—this is called intraspecific communication. The songs are performed near the territory boundary to drive away potential intruders.
The songs are complex and can be broken down into an introduction call, a great call, and various interlude sequences.
The introduction call is a song performed by both members of the pair. The great call is a song always initiated by the female and answered by the male. The interlude sequences can be a song performed by both members of the pair or can also be a song initiated by the female and answered by the male. Generally, the young do not participate in the vocalizations.
Their long limbs enable a unique form of movement called brachiation. This means they move by swinging their bodies from one branch to another.
White-handed gibbons are both allo- and auto-groomed animals. This means they groom themselves and also groom each other among different individuals in the group. On average, they spend ten hours a day grooming. For lar gibbons, allogrooming is a behavior with a hygienic purpose rather than a social one, unlike what is observed in other primates.
Lar gibbons spend more than 15 hours per day in the trees used as sleeping sites for the night. This behavior reduces the risk of predation. Once in these trees, the gibbons stop singing and remain as calm as possible to avoid detection by predators.
Group size varies by latitude: Populations in the north consist of groups of 4-5 individuals, while those in the south have groups of 2-3 individuals. Home ranges measure between 17 and 40 hectares and are defended when different groups of gibbons meet.
