Usually a single young is born. There is a limited amount of data on the mating of this species. Males initiate mating more frequently than females. If the female is willing to mate, she bends forward in acceptance. Behavior The gray gibbon is very agile.
Gray gibbons travel mostly in trees by swinging from branch to branch.
They move by brachiation, which means they extend their long arms over their head in order to hook their hands onto branches. The gray gibbon moves quickly with long leaps and swings. They are able to cover 3 meters in a single swing and around 850 meters per day. Grey gibbons walk upright with hands over head for balance when walking on the ground, although they do not cover long distances in this fashion. The gray gibbon is not a good swimmer and avoids open water.