Sumatran orangutans start crafting their engineering skills as infants

By 6 months old, young orangutans are experimenting with construction materials, and by 6 years old, they are building platforms 20 meters in the air.

Sumatran orangutans start crafting their engineering skills as infants
Orangutans devote years of practice to nest building, an essential skill for life in the treetops. Sumatran orangutans start learning the skill at as young as 6 months old, a new study finds. ROMEO GACAD/AFP VIA GETTY IMAGES

At six months old, human infants are still working on sitting up by themselves. But baby orangutans at that age are already developing their engineering skills.

Orangutans build complex sleeping platforms as high as 20 meters in the tree canopy — the equivalent of four stories above the ground — every single evening. The nests are intricate and can include woven elements, pillows, blankets, padding and roofs to protect from rain.

But nest building isn’t instinctive to orangutans — it has to be learned through years of (sometimes hilarious) trial and error that start in infancy, researchers report in the May Animal Behaviour. The finding could be important for conserving populations of the critically endangered ape.

The treetops are “a dangerous place to live when you’re so big and heavy,” and a poorly made nest can spell disaster, says Andrea Permana, a primatologist at the University of Warwick in England.

To see how orangutans become expert canopy architects, Permana and her colleagues tracked the development of 27 young Sumatran orangutans at the Suaq Balimbing monitoring station in Sumatra, Indonesia, over 13 years. Those observations allowed the researchers to create detailed timeline of how nest building emerges.  

By 6 months of age, baby orangutans take an active interest in nest building, even adding leaves and twigs to mom’s nest.

Young orangutans begin by building “day nests” — temporary platforms, often in fruit trees, for lounging while foraging. “Sometime before their first birthday, they’ve already started to try and bend branches around in a circle to try and make a nest foundation,” Permana says.

At this age, they’re not always strong enough to get the job done. “They’ll hang on [a branch] with their body weight to try and break it, really pulling, trying to bend it,” Permana says. “They think they’ve made a circle and they let go and it just pings open. You can see they’re kind of surprised, like ‘Oh! It’s not as easy as it looks.’”