Human senses and AI have combined to uncover hidden patterns in the roars, sighs and other noises made by Indonesia’s orangutans – and may lead to people understanding what the great apes are actually saying.
The team from Cornell University in the US pooled together a dataset of 117 recorded ‘long calls’ – a series of long booming pulses and grumbles that can be heard over long distances of up to 1 kilometer through dense jungle – made by 13 male Bornean orangutans.
Researchers from the study, showed ‘a continuous gradation of sounds across phases and pulses,’ suggesting orangutans can modulate their voices precisely.
‘These features would seem to greatly boost the potential complexity of this signal,’ they wrote, suggesting humanity might soon know what is being communicated.
All these distinct phases and pulses, the team wrote, can be ‘combined into variable sequences within a single long call vocalisation,’ meaning that the male apes’ with their ‘long calls’ very likely communicate complex messages to one another.
The long call serves as a means for males to attract females and advertise their presence to other males, playing an important role in orangutan social communication.
‘Our research aimed to unravel the complexities of orangutan long calls, which play a crucial role in their communication across vast distances in the dense rainforests of Indonesia,’ the study’s lead author, Dr Wendy Erb said.
‘We are fairly confident there is much complexity still to unpack in this great ape’s vocal system.’
Decoding Orangutans
The team used a state-of-the-art unsupervised machine learning algorithm, Uniform Manifold Approximation and Projection (UMAP), that had shown success decoding ‘animal vocal repertoires’ for the University of California, San Diego back in 2020.
Erb said: ‘Through a combination of supervised and unsupervised analytical methods we identified three distinct pulse types that were well differentiated by both humans and machines.’
The names of those three pulse types, as given by the researchers to help steer future study, were: ‘Roar’ to define high-frequency pulses, ‘Sigh’ meaning low-frequency pulses, and ‘Intermediate’ to catch any and all pulses that fell between those two previous categories.
This ability to distinguish and differentiate between the unique sounds that orangutans make will be the next project for those hoping to one day understand and perhaps speak with humanity’s primate cousins.
‘While our study represents a significant step forward in understanding orangutan communication, there is still much to uncover,’ Erb said. ‘Orangutans may possess a far greater repertoire of sound types than we have described, highlighting the complexity of their vocal system.’
Orangutans Self Medicate
Meanwhile, for the first time a wild animal has been observed treating open wounds with a substance known to have medicinal properties.
Researchers say they observed a male Sumatran orangutan treating an open facial wound with sap and chewed leaves from a plant known to have anti-inflammatory and pain-relieving properties.
The Max Planck Institute of Animal Behavior in Germany, describe how, while tracking a male Sumatran orangutan called Rakus, they noticed he had a fresh facial wound – probably the result of fighting another male.
Three days later, he was seen feeding on the stem and leaves of Fibraurea tinctoria – a type of liana climbing vine.
‘Thirteen minutes after Rakus had started feeding on the liana, he began chewing the leaves without swallowing them and using his fingers to apply the plant juice from his mouth directly on to his facial wound,’ the researchers said.
The team say the plant used by Rakus, and related liana species, are used in traditional medicine to treat various diseases, such as dysentery, diabetes and malaria.
