The agile gibbon (Hylobates agilis) is a gibbon distributed in the tropical evergreen forests of Thailand, Malaysia, and the island of Sumatra. Using its long arms and slender hands, it moves rapidly between trees by brachiation, and on the ground it walks bipedally awkwardly. It is diurnal and primarily eats fruit, young leaves, and insects. It lives in small family groups centered on a pair that maintain a territory; in the morning the male and female sing for long periods with divided roles to indicate territory and family bonds. Its population has declined due to habitat destruction and poaching, and it is classified as Endangered (IUCN Red List category I B).