We stood in the warm twilight of Borneo, in the Sepilok Orangutan Rehabilitation Centre in Sabah. The orang-utans had made their nests for the night and the piercing wails of the cicadas that started at sunset were slowly abating into a background throb of noise.

We were in a small group with one guide. We sat outside the orphan nursery on a damp slope, binoculars being passed round, pressed tightly to eyes and then passed on again. We were watching as the flying squirrels made their ‘leap of faith’. They would come out from their nests and scurry up the tree until, with a sudden thrust, they would launch into the night, their large bodies silhouetted against the darkening sky.

This was when our group would let out a collective sigh of wonderment as we watched these cat-sized creatures elegantly soaring through the tangled canopy. It was then that we first heard it. The sound is unlike any other I had ever heard.

Dr Brigitte Spillmann has described it as ‘a series of long booming pulses and grumbles, which can be heard through more than 1 km of dense jungle.”

However, nothing can compare with the feeling of hearing this call. It reverberates through your body.

“If he had stayed quietly in his throne of leaves, we would have been unaware of the regal presence mere metres above us.”

Upon hearing this, the guide whispered frantically into his walkie talkie. Within moments, swarms of excitable guides were materialising, weaving their way through the trees with the nimbleness and grace that only experienced forest dwellers possess. We knew this was special. In the excitement, we soon interpreted that that the male had never been seen before. He was wild.

It is not unusual for a dominant male to leave his nest if he has been disturbed. Regretfully, he must have obviously felt unsettled by the throng of binocular wielding apes that stood searching for flying squirrels and so he abandoned his nest and began to ‘long call’ in an attempt to dissuade us.

If he had stayed quietly in his throne of leaves, we would have been unaware of the regal presence mere metres above us.

Orangutan anger!

He soon came down, his eyes ablaze with the anger that any human will know if they have been disturbed from deep sleep. His flanges protruded from his cheeks. His body was massive, drenched in thick orange hair. His hands were easily larger than my head and we watched in admiration as this king of the jungle attempted to proceed towards us.

Fortunately, the shoots that he used to try and swing towards were much too delicate for this mighty king. When his anger had heightened into a boiling rage, we were ushered away.

Yet, to this day, I can still see this indomitable being glaring at us through the foliage. It was an experience I could never forget.