HOW DO ORANGUTANS ‘TALK’?

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 the use of vocalisations*.

The vocalisations made by orangutans differ from those of other primates. Adult orangutans will emit long-range vocalisations to reach other individuals that are scattered throughout the dense rainforest. These vocalisations play an important role in defining individual orangutan relationships and social interactions, including for reproduction. Vocalisations are also used to convey complex emotions, such as fear, aggression, and excitement. 

Also read: HOW TO MAKE BABY ORANGUTANS 101

One of the orangutan vocalisations is the ‘grunt’, which is emitted as a low snort. At times, grunts can be heard from immature male and female orangutans as they play. In some cases, grunts are also voiced by males without cheek-pads as a sign 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. This vocalisation is typically used by baby orangutans to request food or indicate they want to suckle from their mothers. The scream is also emitted by young orangutans when they feel distressed. 

A vocalisation that can be heard echoing throughout the forest is known as the ‘long call’, which is used to establish the domain of male adult orangutans with cheek-pads. Long calls are sent out by adult males to attract the attention of female orangutans and to prevent other males from entering their territory. They can be heard 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 itself usually consists of three parts, an initial grunt or grumble, followed by a climax, then an ending that sounds like a low gurgle, and is quite 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.

The ‘kiss-squeak’ vocalisation is often used by wild orangutans, both male and female. This sound is produced by pursing the lips together to form a trumpet, which then 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 have also been observed practicing kiss-squeaks. Orangutans will often shake the branches of trees while they are kiss-squeaking to get their message clearly across 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. A grumble can only be heard from a fairly close distance, has no pattern, and is repeated quickly. In fact, the grumble 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 have also been known to release grumbles to signal their annoyance at being disturbed. When copulating, males without cheek-pads will also let out grumble sounds to indicate pleasure. 

Footnote:
•    Vocalisations are chants, calls, shouts, and other sounds emitted by animals to communicate with others.