When on the ground, Siamangs are more or less bipedal. When in the trees however (which is about 80% of the time) they move by brachiation, which is hand over hand swinging. During this movement, they are able to carry things with their feet. Their arm span can be as large as 1.5m.
One of the most interesting facts about the Siamang is that it is a species that forms monogamous bonds. This is rare for an ape. They live in family groups comprised of that pair and up to four children. They forage for food together (mostly leaves and fruits, but sometimes insects and birds) and groom each other. Siamangs have a gestation period of 7.5 months, and the young are born quite helpless. They will not be weaned for two years and after that they continue to stay with the parents for a bit longer.