Young orangutans who spend little time working out for themselves how to build a broad diet can partly compensate by watching how other orangutans choose what to eat.

The findings suggest that orangutans have different strategies for developing broad survival skills, says at the Max Planck Institute of Animal Behavior in Germany.

Young orangutans acquire a substantial body of knowledge before they can survive independently, which they must do by the time they are 8.5 years old. This includes understanding what foods are safe to eat, where to find them and how to process them in a rainforest offering hundreds of food options of varying levels of accessibility – from easy-to-access leaves to the more inaccessible but also more nutritious seeds at the heart of a tough, spiny neesia fruit.

Scientists already know that orangutans can acquire this knowledge both by observing their mothers and other individuals in their social circle – a process known as social learning – and by exploring entirely on their own without any input from others, which is known as individual learning. But how these two forms of learning work together – and how they affect what orangutans learn to eat before becoming independent – hasn’t been clear.

To find out, Thillaikumar and her colleagues analysed nearly 7000 instances of learning recorded during more than 1700 hours of observations of wild Sumatran orangutans at Suaq Balimbing, a research station in Indonesia. The observations, collected over 12 years, tracked 21 youngsters as they closely watched other orangutans who were interacting with foods and other objects.

The young apes varied considerably in how much they relied on different kinds of learning, with some using more social learning, and others exploring independently much more often. This might, in part, reflect personality differences, and might also be influenced by early development – including differences in how mothers care for their young, says Thillaikumar.

Youngsters who learned by watching others also tended to continue manipulating new objects or trying new foods for about 145 minutes after they had closely observed another orangutan. This activity is reminiscent of the way in which children will spend time imitating an activity they have just seen demonstrated by an adult, says Thillaikumar. “Yeah, it’s practice.”

Next, the researchers drew on about 4700 hours of feeding observations for 13 of the youngsters to estimate the range of foods they had learned to eat by the time they reached independence. Unsurprisingly, the team found that the individuals who had engaged in plenty of social learning and plenty of individual learning had acquired the broadest diets.

But they also found that young orangutans who engaged in very little truly individual learning could partially compensate and develop a reasonably broad diet if they were good social learners.

Orangutan is first non-human seen treating wounds with medicinal plant

A male Sumatran orangutan chewed the leaves of a plant used in Indonesian traditional medicine and placed them on a wound on his face

at Duke University in North Carolina says she’s impressed by the sheer scale of the work, following young orangutans through the rainforest across their entire, lengthy period of dependency on adults. She was particularly intrigued by how often social observation was followed by young orangutans practising the techniques they had observed. “In simpler terms, they show clearly what we see in human children and other apes – that they watch others perform a behaviour and then go try it out on their own.”

The variability in learning styles – even at an individual level – is especially interesting, says , also at Duke University. It suggests that no single form of learning can tell the whole story. “Predicting dietary breadth at maturity requires looking at all types of learning.”

Some chimpanzees seem to use sexual behaviour like genital rubbing to manage stressful situations, which shows they aren’t as different from hypersexual bonobos – our other closest living ape relatives – or, indeed, people as we thought.

at Durham University, UK, and his colleagues have investigated the sexual behaviour of non-human primates at the in the Democratic Republic of the Congo and the in Zambia. Both sanctuaries include a mix of wild and captive-born apes that can roam and forage freely within them.

The researchers observed 53 bonobos (Pan paniscus) across three groups at Lola ya Bonobo and 75 chimpanzees (Pan troglodytes) across two groups at Chimfunshi in the course of feeding events that involved a swing distributing a limited supply of peanuts over a particular area.

“Bonobos and chimpanzees both live in very complex social structures with very rich social interactions that they have to navigate on a daily basis,” says team member , also at Durham University. Anticipating such feeding events can be stressful because of competition over who gets to the food first.

The researchers observed 107 instances of genital contact in the bonobos and 201 in the chimpanzees in the 5 minutes before 45 feeding events across the five groups.

“This is either putting a hand or foot onto another primate’s anogenital region and it also might involve the genitals touching each other, like the genital rubbing behaviour that bonobos are very famous for,” says Brooker.

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The study also revealed differences between the species: “We found the frequency of sex in these situations was more common in female bonobos with other females, whereas it was more common among males in chimps,” says Clay. That may be linked to the fact that bonobos live in matriarchal groups, while chimpanzees live in patriarchal ones, she says.

“Using sex as a social tool to navigate all sorts of social problems has given bonobos a bit of a reputation as a sort of sexy, hippie ape,” says Clay. “This work shows us that the differences between the two species are maybe not as big as was previously assumed. Chimpanzees, although they’re known to be aggressive and violent, actually have a really rich repertoire of behaviours that they use to manage their social lives.”

“Chimps have definitely drawn the PR short straw by comparison to bonobos,” says at the University of Oxford.

The chimps use sex in a way that goes beyond reproduction and although it is different from sexuality in humans, we also don’t just have sex for reproduction, says Clay. For instance, has been given as a reason people have sex.

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at the University of Bristol, UK, wonders whether the same level of behaviour would be seen in wild settings rather than sanctuaries.

The work may also shed light on our last common ancestor, which lived some 5 million to 7 million years ago, before humans diverged from chimps and bonobos, he says.

“Given that all three species use sexual behaviours to navigate social relationships, the common ancestor we share likely did too,” says Brindle.

Bonobos are quick to help a person who doesn’t know what they know, a sign that they can deduce the mental states of others.

The capacity to think about what others are thinking, known as , is an essential skill that allows humans to navigate their social worlds. It enables us to recognise that someone may hold different beliefs or perspectives to our own, underpinning our ability to understand and help others appropriately.

The question of whether our closest living relatives also have theory of mind has been hotly debated for decades. Despite some , non-human great apes seem to have some aspects of this capacity, suggesting it is more evolutionarily ancient than once thought. For example, wild chimpanzees that see a nearby snake, albeit a fake one, seem to call out to they know haven’t already seen it.

But we have been missing clear evidence from controlled settings that primates can track a perspective that differs from their own and then act upon it, says at Johns Hopkins University in Maryland.

To investigate this, Townrow and , also at Johns Hopkins University, tested if three male bonobos at the Ape Initiative research centre in Iowa could identify ignorance in someone they were trying to cooperate with, and then gesture to them to help solve the task.

On a table between the bonobo and an experimenter were three upturned plastic cups. A second researcher placed a barrier between the experimenter and the cups, then hid a treat, like a juicy grape, under one of them.

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In one version of the experiment, the “knowledge condition”, a window in the barrier allowed the experimenter to watch where the treat was placed. In the “ignorance condition”, their view was completely blocked. If the experimenter found the food, they would give it to the bonobo, providing a motivation for the apes to share what they knew.

Townrow and Krupenye looked at whether the ape pointed at the cup, and how quickly they pointed, after the barrier had been removed over 24 trials for each condition.

They found that, on average, the bonobos took 1.5 seconds less time to point and pointed in approximately 20 per cent more trials in the ignorance condition. “This shows that they can actually take action when they realise that somebody has a different perspective from their own,” says Krupenye. It appears that bonobos understand features of what others are thinking that researchers have historically assumed they didn’t comprehend, he adds.

This simple yet powerful research gives experimental support to existing findings from wild apes, says at Durham University, UK. However, she warns that the findings may not apply to all bonobos because the study animals were raised in human-oriented environments. But that doesn’t detract from the results demonstrating that a capacity is there, she adds.

Indeed, finding this capacity in these three bonobos indicates that the potential exists within their biology and, very likely then, the biology of our common ancestor as well, says Krupenye.

“It suggests that our ancient human relatives likely also had these abilities and could use them to bolster cooperation and coordination with one another,” says at the University of California, Berkeley. “By understanding when someone may be ignorant, especially about evolutionarily critical information like the location of food, our ancestors could have used these capacities to communicate and coordinate more effectively with their social partners.”

Wild chimpanzees appear to learn skills from each other and then – much as humans do – improve on those techniques from one generation to the next.

In particular, young females that migrate between groups bring their cultural knowledge with them, and groups can combine new techniques with existing ones to get better at foraging for food. Such “cumulative culture” means some chimpanzee communities are becoming more technologically advanced over time – albeit very slowly, says at the University of St Andrews, UK.

“If chimpanzees have some cultural knowledge that the community they’re moving into doesn’t have, they may pass it on – just in the same way they’re passing the genes on,” he says. “And then that culture builds up from there.”

Scientists already knew that chimpanzees were capable of using tools in sophisticated ways and passing on that knowledge to their offspring. But in comparison with the rapid technological development of humans, it seemed that chimpanzees weren’t improving on previous innovations, says Whiten. The fact that chimpanzee tools are often made from biodegrading plants makes it difficult for scientists to track their cultural evolution.

at the University of Zurich in Switzerland suspected she might be able to apply genetic analysis to the puzzle. While male chimpanzees stay in their home area, young females leave their native communities to find mates elsewhere. She wondered if those females have brought their skill sets with them into their new groups.

To find out, she and her colleagues acquired data on 240 chimpanzees representing all four subspecies, which were at 35 study sites in Africa. The data included precise information about what tools, if any, each of the animals used, and their genetic connections over the past 15,000 years. “The genetics give us a kind of time machine into the way culture has been transmitted across chimpanzees in the past,” says Whiten. “It’s quite a revelation that we can have these new insights.”

Some chimpanzees used complex combinations of tools, for example a drilling stick and a fishing brush fashioned by pulling a plant stem between their teeth, for hunting termites. The researchers found that the chimpanzees with the most advanced tool sets were three to five times more likely to share the same DNA than those that used simple tools or no tools at all, even though they might live thousands of kilometres away. And advanced tool use was also more strongly associated with female migration compared with simple or no tool use.

“Our interpretation is that these complex tool sets are really invented by perhaps building on a simpler form from before, and therefore they have to depend on transmission by females from the communities that invented them initially to all the other communities along the way,” says Whiten.

“It shows that complex tools would rely on social exchanges across groups – which is very surprising and exciting,” says Gunasekaram.

at the University of Geneva isn’t surprised by the results, but says the definition of complex behaviour is debatable.  “After working with chimps for 20 years, I would argue that stick use itself is complex,” he says.

His own team, for example, found what they called cumulative culture in chimpanzees that make sponges out of moss instead of leaves – which is no more complex, but . “It’s not a question of being more complex, but of just having a technique that builds on a previously established one,” he says.

Cumulative culture is still markedly slower in chimpanzees compared with humans, probably due to their different cognitive abilities and lack of speech, says Gunasekaram. Also, chimpanzees interact far less with others outside their communities compared with humans, giving them fewer opportunities to share culture.

Several plants eaten by chimpanzees when they are ill or wounded have been found to have medicinal effects, providing some of the strongest evidence yet that our close relatives practise self-medication.

Reports of chimpanzees self-medicating with plants have been around for decades, but it is difficult to establish when wild animals are ill and what effect their diet has.

at the University of Oxford and her colleagues followed wild chimps through Budongo Forest in Uganda, recording when they were ill and what they ate. The researchers identified chimps with obvious wounds or with gut infections by analysing their faeces for signs of intestinal worms, as well as checking urine samples for raised levels of immune cells.

Analysis of 53 extracts of plants consumed by the ill or injured chimps showed that 88 per cent were active against bacteria that are pathogenic in humans, including antibiotic-resistant strains like MRSA. Extracts from every sampled species had anti-inflammatory effects.

Such a systematic approach allowed the researchers to identify and characterise the species that the chimps use beyond what had been done before, says at the University of St Andrews, UK, who wasn’t involved in the study. “It’s a very impressive project.”

Sick chimps often left the safety of their group to eat specific plants, and picked out species only rarely eaten at the site. The infrequency of these events is what makes self-medication behaviour so hard to observe, but also provides one of the strongest pieces of evidence that it is a targeted response to illness.

Chimpanzees are usually reluctant to try unfamiliar foods that might be dangerous, says Freymann. Choosing to eat unusual plants therefore suggests they have particular reasons for doing so. “If you’re sick, you’re not going around stuffing things that could make you sicker in your mouth,” she says.

This might not capture everything that is going on, though, says Graham, as chimps’ diets are still very diverse. If the animals learn which plants to eat from others, over generations the community might overcome this reticence towards new foods. Directly comparing the diets of sick and healthy chimps at the same time might clarify whether these are active choices, she suggests.

Team member at the Brandenburg University of Applied Sciences in Germany hopes that identifying the active compounds in the plant extracts might lead to promising candidates for human medicines. “What if human lives can be saved by following the ways of our animal relatives?” he says.

An orangutan, another member of the great ape family, was seen applying plant leaves directly onto a wound in an apparent act of self-medication reported this year.

A tiny, vegetarian great ape may have lived in western Europe 11.6 million years ago. Smaller and lighter than any other known great ape, the newly discovered 10-kilogram primate was a skilled climber that probably ate leaves, says at the University of Tübingen in Germany.

“It’s quite a small primate,” she says. “But it differs from all known fossils and, of course, all living great apes we know so far.”

About 15 million years ago, in the middle of the Miocene Epoch, hominoids – the great apes – became rarer in Africa and more abundant in Europe. While they sometimes shared habitats with other primates such as pliopithecoids – extinct cousins of apes and Old World monkeys – hominoid species didn’t appear to coexist with each other in Europe.

In 2019, Böhme and her colleagues reported the discovery of 37 bones at Bavaria’s Hammerschmiede archaeological site that appeared to come from an early bipedal ape from 11.6 million years ago, which they named Danuvius guggenmosi.

During the excavations, Böhme was surprised when she found two tiny, ape-like teeth and a kneecap in the same layer of sediment as the Danuvius fossils.

“We kept saying: ‘What is this?’” she says of these smaller fossils. “And then we decided, OK, it’s clear: this is something new.”

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The fossils are too old for DNA analysis, says Böhme. So the researchers took detailed measurements of the 7-millimetre-long molar and the 16-millimetre-wide kneecap, both from a juvenile, as well as a smaller premolar fragment, which they say came from a young adult. They also calculated the thickness of the enamel and ran microscopic CT scanning of the teeth.

The thin enamel, like that of gorillas, suggests a soft diet probably composed of leaves, says Böhme. The shape, thickness and ligament attachment sites of the kneecap resemble those of tree-living primates, hinting that the ape was a proficient climber.

The researchers named the new ape Buronius manfredschmidi, after the medieval name of a city near the Hammerschmiede site, and a dentist named Manfred Schmid who has been collecting fossils from the site since the 1970s.

Lack of competition for resources might explain why the Buronius and Danuvius apes could live together, says Böhme – Danuvius is thought to have eaten hard foods like nuts and possibly meat. The team cannot rule out the possibility that the larger ape, which might have been up to three times heavier, may have sometimes fed on the smaller species, she adds.

However, the three fossils might not be sufficient to make such “grandiloquent” conclusions, says at the American Museum of Natural History in New York City. “Could the smaller fossil elements belong to an infantile Danuvius individual?” he asks. “The teeth certainly look like they could be deciduous [baby teeth].”

He also wonders whether the kneecap represents the same species as the teeth. “Even though it is suggested that it belongs to a juvenile individual, its size overlaps with the lower range of adult orangutans [which are much larger apes],” says Almécija.

at the University of Bordeaux, in France, also has doubts. “It is not very clear to me if the teeth – and in particular the molar – belong to the hominoids or to another primate superfamily, the pliopithecoids.”

Böhme and her colleagues say their comparisons ruled out the possibility that the teeth are baby teeth or pliopithecoid teeth.

In any case, the possibility that two primate species shared the same habitat and perhaps even interacted with each other is a “fantastic discovery”, says Zanolli. “This shows once again that, at that time, Europe was a luxurious and hospitable place for primates to evolve.”

An orangutan has been seen applying the leaves of a plant commonly used in traditional medicine to a cut on its face, seemingly to hasten healing. It is the first case in the scientific record of a non-human animal using a plant with proven therapeutic properties on an open wound.

There have been several previous reports of great apes attempting to self-medicate in other ways. Gorillas, chimpanzees and bonobos, for example, sometimes swallow whole leaves from Aspilia plants to get rid of intestinal parasites. In 2022, a community of chimpanzees in Gabon was seen putting insects onto their open wounds, potentially as a form of first aid.

In the latest study, at the Max Planck Institute of Animal Behaviour, Germany, and her colleagues noticed a fresh gash on the cheek of a male Sumatran orangutan (Pongo abelii) called Rakus, living in Gunung Leuser National Park in Indonesia.

“Rakus was injured, most likely in a fight with a neighbouring male,” says Laumer.

Around three days after the fight, the team spotted Rakus chewing on the stem and leaves of an evergreen climbing plant called akar kuning (Fibraurea tinctoria) and swallowing them. But after 13 minutes of feeding, the ape stopped eating and instead smeared the chewed-up plant across his open wound.

“This went on for 7 minutes,” says Laumer. “He repeatedly put the plant precisely onto the wound, and no other body parts, and then continued feeding on it for half an hour.”

After four days, the wound had closed up. “It was really fast,” she says.

In just a month, Rakus’s cheek was completely healed, leaving behind a faint scar.

The healing process was probably accelerated by the plant, says Laumer, which has been found to have antibacterial, anti-inflammatory, anti-fungal and antioxidant properties. It is also commonly used by local people to treat conditions such as malaria and jaundice.

“To our knowledge, this is the first report of a wild animal precisely treating his wound with quite a potent, medical plant,” says Laumer.

“This is really wonderful to see,” says at Osnabrück University in Germany. “Of course, it’s only one case. So, there are still so many questions: Is this a behaviour he would do again? Is this a behaviour other individuals of his group would do?”