These gibbons were filmed singing after climbing to the top of the jungle canopy.

The primates clambered to the top of the trees inside the Cambodia Wildlife Sanctuary in Siem Reap on December 29.

The filmer, a worker from the organisation, said: ''When you volunteer or visit our sanctuary you will be sure to see and hear our gibbons, they swing through the trees with the gracefulness of ballerinas and sing like they are classically trained.''

Although often confused for monkeys, gibbons are in fact apes and, like all members of that group, have no tail.