JAKARTA: It was deep in the heart of an Indonesian rainforest in West Java that Rahayu Oktaviani, known as Ayu, first heard the “song” of the Javan gibbon.

She had her first encounter in 2008 while visiting the Mount Halimun Salak National Park for an undergraduate research project that required her to obtain a voice sample of the primate.

After waiting patiently for two weeks, coming in and out of the forest, she finally heard a Javan gibbon make its distinctive call.

She recalled how the sound she described as melodic and haunting had created a hush, as it echoed throughout the forest.

“It’s like the most beautiful song that I ever heard in my life. It’s so amazing,” Ayu told Arab News.