Photo by Verna Case
Taken at the National Zoo, in Washington, D.C.
Gibbons demonstrate quite limited altruism compared to many mammals, though they do have some social cooperation within their family groups.
Social cooperation is most prominent in feeding behavior. Though gibbons do much foraging independently, probably to make best use of small and spread-out resources (Gittins 1982), they do have some food-transfer behavior. This often occurs when one gibbon "requests" food from another gibbon from the same family group who is carrying some food (Fisher & Geissmann 1990). Gibbons also allogroom (Fisher & Geissmann 1990). Neither of these activities come at a great cost to the doer, so they would be examples of cooperation.
Care of offspring by older siblings is sometimes observed in captivity, but again, gibbons have primarily maternal care (Geissmann & Braendle 1996).