Orangutans use their hands to alter their voices and make themselves sound bigger, say scientists.

The animals cup their mouths when they produce kiss squeaks – alarm calls that often signify a predator is nearby.

Researchers have now studied the acoustics of these «hand-modified kiss squeaks» and shown that the animals sound bigger and «more impressive» when they use their hands in the call.

«Orangutans cup their mouths to alter their voices«, Victoria Gill, BBC News.