After a few minutes, the young male awakened and sat up. Instantly, Toba opened his eyes and tugged on his son’s fur. The young animal obediently started to groom his father, carefully picking through Toba’s fur, separating the hairs and removing small bits of dirt. This activity was pleasant and relaxing as well as useful for both animals. Grooming one another kept the siamangs clean and reinforced their family ties, too.
Next Singkil began to stir. She noticed her small sister playing on the vine and began to move toward her. Suddenly Tarag was wide awake. Every muscle in her body tensed, and she started to open and close her mouth rapidly, smacking her lips together. She was obviously angry. Singkil recognized the threat and quickly retreated to her sleeping place. Eyeing her mother, she showed her distress by holding her arms out sideways, then shaking her head, hands, and arms repeatedly for nearly a minute.
Neither Tarag nor Toba objected to Singkil’s participation in the family calling. The siamangs’ morning calls began when, half an hour after waking up, Toba inflated his throat sac--a pouch of hairless skin that usually hung in loose folds beneath the animal’s chin. Uninflated, the sac lay almost hidden in the siamang’s fur. But when Toba breathed in a great gulp of air to inflate it, the throat sac bulged like a giant balloon, looking ready to burst. The throat sac acted as a sound amplifier, enabling siamang calls to be heard for great distances.
Toba began with single deep booming noises. Soon, Tarag joined in with booms of her own. Toba’s calling changed to a series of short barks, as if he were giving a “call to attention.” Tarag began to make barking noises which rapidly grew louder and faster. Meanwhile, Toba’s calls consisted of long screams and barks. When Tarag’s barking reached its peak, Toba let out a loud ya-hoo. This seemed to be a signal to the three youngsters to join in. With their smaller throat sacs, the young siamangs made clear, bell-like calls.
As the calling continued, the siamangs grew more and more excited. They ran upright along the branches, their hands held high above their heads. They swung on vines, using one, two, three, or four limbs. They moved quickly through the branches in the arm-over-arm motion called brachiation.
No matter how often Rami witnessed the siamangs’ calling, he found it exciting and astonishing. He watched and listened for twenty-five minutes, until the callling subsided and was taken up by another siamang family nearby. Then, with the siamangs’ song still echoing in his ears, Rami moved off in search of wild cinnamon.
