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Experts unlock the mysteries of orangutan communication

A recent study led by Cornell University has investigated the complex vocal patterns of Bornean orangutans, offering fresh insights into their communication skills. 

Conducted under the guidance of Dr. Wendy Erb from the K. Lisa Yang Center for Conservation Bioacoustics at the Cornell Lab of Ornithology, the research revealed significant diversity and variability in the long call vocalizations of these apes.

Bornean orangutan communication 

Known for their intricate social behaviors and vocal abilities, the Bornean orangutans of Southeast Asia have always intrigued scientists. 

In this innovative research project, Erb and her colleagues aimed to decode the vocal intricacies of orangutans in order to shed new light on how these fascinating creatures communicate.

“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. Over the course of three years, we accumulated hundreds of long call recordings, revealing a fascinating array of vocal diversity,” Erb explained.

How the research was conducted 

The experts used a multidimensional approach, blending traditional audio-visual techniques with advanced machine learning tools. 

By analyzing the long calls of 13 individual orangutans, the researchers sought to categorize the pulse types within these vocalizations and assess their variations.

“Through a combination of supervised and unsupervised analytical methods, we identified three distinct pulse types that were well differentiated by both humans and machines,” Erb said. 

Step forward in understanding orangutan communication 

“While our study represents a significant step forward in understanding orangutan communication, there is still much to uncover. Orangutans may possess a far greater repertoire of sound types than we have described, highlighting the complexity of their vocal system.”

“This study represents the culmination of months of hard work and collaboration, demonstrating the power of collective effort in advancing our understanding of nature’s intricacies. We hope that our findings inspire further exploration of vocal complexity across different species and pave the way for future discoveries in animal communication,” noted Erb.

Complexity of the system

“We found low inter-observer reliability and poor classification accuracy using supervised approaches, indicating that pulse types were not discrete,” noted the study authors. 

“We propose a new pulse type classification scheme that is highly reproducible across observers and exhibits high classification accuracy using support vector machines. Although the low number of call types suggests long calls are fairly simple, the continuous gradation of sounds seems to greatly boost the complexity of this system.”

More about orangutan communication 

Orangutan communication involves a variety of vocalizations, gestures, and facial expressions. One of the most distinctive vocalizations is the “long call,” used primarily by male orangutans to attract mates and assert dominance, effectively communicating across the dense forests they inhabit.

Gestures and facial expressions

Additionally, orangutans use a range of gestures – both subtle and overt – to convey messages. These can be as simple as a pointing gesture to direct the attention of others or as complex as pretending to be hurt to gain sympathy. 

Facial expressions are also vital, with different configurations of the eyes, eyebrows, and mouth conveying emotions such as happiness, surprise, or aggression.

Mother orangutans 

Interestingly, mother orangutans also communicate with their offspring through gentle touches and sounds, guiding and teaching them as they grow. This communication is essential for the survival skills the young orangutans need to acquire. 

Communication among orangutans is deeply intertwined with their social structure and environmental interactions, showcasing their intelligence and adaptability.

Social lives of orangutans

Orangutans are somewhat unique among great apes due to their semi-solitary nature. Unlike the more social chimpanzees and gorillas, adult orangutans tend to spend a lot of their time alone. However, this doesn’t mean they lack social interactions or complex social lives.

Female orangutans 

Female orangutans are often accompanied by their young. Mothers are highly nurturing, investing a significant amount of time in their offspring – orangutan infants stay with their mothers for up to eight years, one of the longest dependencies in the animal kingdom. 

During this period, mothers teach them essential skills for survival, such as foraging and nest building.

Male orangutans 

Male orangutans, on the other hand, are more solitary but not completely devoid of social connections. They interact with females for mating purposes and may engage with other males in displays of dominance, especially when it comes to establishing territory. 

The interactions among males can range from aggressive confrontations to more passive avoidance.

Group gatherings

Social interactions also occur more frequently during periods of high fruit abundance, when orangutans might temporarily converge in small groups. These gatherings allow for social play among juveniles and social learning opportunities. 

Communication during these times is crucial and can be quite sophisticated, involving a variety of vocalizations, gestures, and body language.

While orangutans may not form the tight-knit groups seen in other primate species, their social lives are rich and complex, characterized by deep maternal bonds, occasional social gatherings, and significant interactions that shape their behavior and survival strategies in the wild.

The Cornell study is published in the journal PeerJ.


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