Why orangutans cup their mouths to sound an alarm

Orangutans, pictured here in in the Ketambe area of Sumatra, Indonesia, learn from their elders to use alarm calls to signal distress and scare off predators.
Perry van Duijnhoven
Orangutans, pictured here in in the Ketambe area of Sumatra, Indonesia, learn from their elders to use alarm calls to signal distress and scare off predators.
Perry van Duijnhoven