Orangutans are pretty darn smart. That we’ve long known. Yet they are even smarter than we’ve thought.
Take, for instance, recent findings by researchers that orangutans living in the wild in Borneo self-medicate by using specific plants. The forest-dwelling apes treat inflammation of their joints and muscles by chewing leaves of the Dracaena cantleyi plant. The orangutans, whose name in Malay means “people of the forest” in a recognition of their similarity to humans, masticate on the leaves until they turn into a lathery pulp, which the apes then proceed to smear on their aching body parts for between 15 and 45 minutes.
During the observations the apes never swallowed the leaves, indicating they were using the plant only for their medicinal properties. Laboratory tests performed later on the leaves have shown that their extracts can inhibit the production of so-called inflammatory cytokine molecules that promote inflammation in the body.
“The use of leaf extracts from Dracaena cantleyi by orang-utan has been observed on several occasions; rubbing a foamy mixture of saliva and leaf onto specific parts of the body,” the researchers, led by Czech expert Ivona Foitova, who has been conducting field research in Borneo for years, explain in a study published last year in the journal Scientific Reports. “Interestingly, the local indigenous human population also use a poultice of these leaves for the relief of body pains,” they add.
The self-medicating behavior of Bornean orangutans was observed during more than 20,000 hours of filming conducted by the Borneo Nature Foundation. In some of the clips the animals were seen making their own herbal medicines in the Sabangau Forest in the Indonesian province of Central Kalimantan.
Of course, orangutans aren’t the only animals that self-medicate. Several other species have been documented doing so. They include African wild chimps, bonobos and gorillas which have been filmed consuming the bitter juices of certain plants to treat their parasite infections.
But here comes some more surprising news about orangutans: they are the only known animals, besides humans, to chew over the past. Orangutans let out a loud “kiss-squeak” whenever they spy a predator like tigers and snakes. The sound is meant to warn other orangutans of the dangers. Many other animals engage in such warning calls, of course, with some species even boasting a vocabulary of specific sounds for specific predators.
Yet researchers now say they have witnessed the orangutans making this call long after predators have passed, which means they seem to tell other orangutans about a danger that took place in the past and is no longer present. Studying orangutan calls in the Ketambe forest in Sumatra, the researchers designed an experiment whereby they clothed themselves variously in a tiger-striped, spotted, and plain sheet. They then lowered themselves to all fours in the forest right beneath lone female orangutans perched on branches above, pretending to be predators like tigers.
Once the orangutans spotted them, the scientists and their assistants would wait around a little, then leave. They expected the orangutans to make an alarm call right there and then, yet the primates did not do so. The first female tested, which had a newborn with her, “stopped what she was doing, grabbed her infant, defecated [a sign of distress], and started slowly climbing higher in the tree,” recalled Adriano Reis e Lameira, a postdoctoral student at the University of St. Andrews in the United Kingdom, who led the research. “She was completely quiet.”
The female orangutan stayed quiet for about 20 minutes before she started making the alarm call, which she did repeatedly for over an hour. “The mother saw the predator as most dangerous to her youngster and chose not to call until it was gone,” argues the scientist, who is the lead author of a study published in Science Advances. Later she did sound the alarm, however, so as to teach her offspring about the danger and how to bring attention to it through calls, he posits.
Other scientists have hailed this discovery as a potential key insight into the first stirrings of human language itself in the distant past. “The results are quite surprising” because this ability to speak about the past “is one of the things that makes language so effective,” commented Carel van Schaik, a primatologist at the University of Zurich in Switzerland.
Yet despite their intelligence, orangutans tend to be treated poorly in their natural habitats in Borneo and Sumatra, two biodiverse islands in Indonesia and Malaysia. Over the past decades they have lost most of their forests to loggers and oil palm cultivators. Poaching and hunting have also taken their toll on wild orangutan populations in the wild. Some locals continue to hunt their primates for their meat and body parts.
Recently a group of researchers, who conducted a 16-year survey in Borneo between 1999 and 2015, has warned that orangutans are facing a form of eco-genocide. In the past two decades alone as many as 100,000 of the critically endangered primates may have died off on the Southeast Asian island as a result of human activities.
“[B]etween 1999 and 2015, half of the (island’s) orangutan population was affected by logging, deforestation, or industrialized plantations,” they write in a paper published last March in the journal Current Biology. “Although land clearance caused the most dramatic rates of decline, it accounted for only a small proportion of the total loss,” they noted. “A much larger number of orangutans were lost in selectively logged and primary forests, where rates of decline were less precipitous, but where far more orangutans are found.”
Not even their great intelligence can save these placid and fascinating primates from our destructive ways.
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