Orangutans are semi-solitary primates who spend the majority of their lives alone. However, in some orangutan populations, the females will gather in groups from time to time, especially during the fruiting season, when forest food is abundant. Group activity like this allows for socialisation among orangutans, and these interactions do require communication. One of the ways that orangutans communicate is through vocalisations – chants, calls, shouts, and other sounds emitted by animals to communicate with each other.
The vocalisations made by orangutans differ from those of other primates. Adult orangutans will emit long-range vocalisations to reach other individuals scattered throughout the dense rainforest. These vocalisations are essential in defining individual orangutan relationships and social interactions, including reproduction. Vocalisations are also used to convey complex emotions, such as fear, aggression, and excitement.
One of the orangutan vocalisations is the ‘grunt’, emitted as a low snort. Immature male and female orangutans grunt as they play. Sometimes, males without cheek pads grunt when they want to copulate with a dominant female. Grunts are also made by orangutans when they make contact with others.
Another vocalisation heard from orangutans is the ‘scream’, which, as its name suggests, sounds like a frightened scream or drawn-out wail. Baby orangutans typically use this vocalisation to request food or indicate they want to suckle from their mothers. The scream is also emitted by young orangutans when they feel distressed.
The Long Call
A vocalisation that can be heard echoing throughout the forest is known as the ‘long call’. Male adult orangutans with cheek pads use it to establish their domain. Adult males send long calls to attract the attention of female orangutans and prevent other males from entering their territory. You can hear them from over 1.5 kilometres away. In some cases, adult males will make spontaneous long calls when responding to disturbances, such as being startled by a falling tree. The long call usually consists of three parts: an initial grunt or grumble, a climax, and an ending that sounds like a low gurgle, often accompanied by a frothy or bubbly mouth. However, some orangutans will omit the grunt or grumble entirely and immediately start with the climactic part.
Wild orangutans often use the ‘kiss-squeak’ vocalisation, both male and female. They produce this sound by pursing the lips together to form a trumpet, which creates a sharp kissing-smacking sound. Orangutans, especially dominant individuals, will emit kiss-squeaks to show their displeasure at human presence or to ward off predators. Baby orangutans also practise kiss-squeaks. Often, orangutans will shake the branches of trees while they are kiss-squeaking to convey their message clearly and scare off any individuals they see as threatening.
The last vocalisation is the ‘grumble’, which sounds similar to the low rumble of a starting machine. You can hear a grumble only from a reasonably close distance. It has no pattern and is repeated quickly. In fact, the grumbling sound is often unperturbed by the respiratory pauses an orangutan makes. Most cheek-padded males will emit grumbles at the beginning of their long calls. Even so, some adult females and males without cheek pads also release grumbles to signal their annoyance at being disturbed. When copulating, males without cheek pads let out grumble sounds to indicate pleasure.
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