Rare footage reveals gorillas’ treetop slumber antics

The bedtime rituals of Grauer’s gorillas have been captured on camera for the first time by filmmakers using military-grade thermal imaging technology

As darkness falls in the forests of Kahuzi-Biega National Park in the Democratic Republic of Congo, a family of Grauer’s gorillas weave together branches and fresh leaves, carefully constructing nests that will give them comfort and support for a night’s deep slumber.

Gorillas' nesting instinct is so strong it has even been reported in captive animals.

This special time in the huge primates’ day has been witnessed in the wild by very few. But footage filmed for a new BBC series 'Gorilla Family & Me' reveals what goes on under the cover of darkness in more detail than ever before.

“To the best of my knowledge this is the first ever filming of gorillas at night, certainly using this kind of camera,” says primatologist and chairman of the Ape Alliance Dr Ian Redmond, a self-professed “gorilla-holic” who began his career as Dian Fossey’s research assistant and introduced Sir David Attenborough to gorillas in the 1970s.

 

The new footage features a family of endangered Grauer’s gorillas (Gorilla beringei graueri), led by a silverback known as Chimanuka, making and settling in their nests in and around a tree.

Even after darkness has completely enveloped the forest, the camera picks out much activity.

Glowing gorilla figures climb in the pitch black to parts of the tree where they feel most comfortable and safe, and continue using their accomplished nest-building skills as darkness falls to make fresh beds, some as high as 20m (66ft) from the ground.

“There’s a lot of decision making going on,” says Redmond, who advised the television team ahead of filming and watched the footage afterwards. If a nest isn’t quite right the gorillas might move around after dark to find a better spot, he suggests.

The overall effect is like a “gorilla dormitory”.

“Some of them are in ‘bunk beds’ which are quite high.”

 

The scene, Redmond suggests, calls to mind the television show The Waltons, which always ended with the family calling goodnight to each other from different parts of the house after lights out. Similarly, gorillas interact vocally and are aware of each other’s movements from their “multi-level bunk beds in this little patch of forest which they spend the night in”.

And on the forest floor sleeps Chimanuka; the more vulnerable members of the family near him including his infant son Marhale, and the baby of the family, Mwira, and his mother.

The other gorillas in the 25-strong clan radiate outwards from the male gorilla’s “centre of security”, says Redmond.

“There aren’t many predators that are going to take on a silverback.”

 

He adds that although male gorillas tend to sleep on the ground, they are perfectly able to climb trees despite their weight (which can be over 225kg or about 500lb).

Unlike primates such as monkeys and gibbons which teeter on branches or rocks to snatch sleep, all great apes – orangutans, chimpanzees, bonobos and gorillas – make nests.

But it is a masterful craft, and some gorillas are better builders than others, with nests varying from “sketchy” to “elaborate” Redmond explains.

“To make a substantial nest that you’re not going to fall out of and that isn’t going to break in the night is quite an art.”

Each night gorillas move to a new nesting site.

Here they make fresh beds by bending branches, tucking leaves underneath and weaving them around. They must also check their nesting spot can support their weight, often choosing parts of a tree with three or four branches growing from the same place.

Infants share their mothers’ nests until they’re about three years old, around the time a younger sibling might come along.

 

Gorillas don’t always sleep in trees. Some mountain gorillas prefer to sleep on the ground, possibly to huddle down in the cool, higher altitude. One of the theories for Grauer’s gorillas choosing to nest in trees, however, is that it could help them avoid biting insects.

But once their beds have been made, gorillas can settle down for a restful night’s sleep.

Close-up shots show in enchanting fine detail slumbering gorillas’ faces and the gentle twitches of their human-like hands.

Redmond says the new footage provides new insights into gorillas’ lives that are difficult to document.

The research period for primatologists is usually from morning to mid-afternoon, sometimes early evening. “But then the gorillas carry on feeding until they build a nest – and the humans leave the gorillas in time to get back to their 'nest',” says Redmond.

Although he didn’t film it, Redmond previously spent a night observing a different family of gorillas, sheltering under a fallen tree nearby. During the evening he watched the gorillas’ feeding intensify at dusk, and in the early hours heard a male hooting and chest beating a few hours after having mated with a female: “Maybe he was just feeling good,” he suggests.

But he says he knew thermal imaging technology “would reveal so much more”.

 

The detail with which he got to see the gorillas’ features for example, stood out to Redmond. “One of the things that jumped out at me was how clearly you see them grasping the branches with their feet,” he tells BBC Earth.

And at the end of their night’s secure slumber, the new footage reveals, the gorillas wake up in the early morning, beating their chests as if to greet each other, ready for a new day in the forest.

‘Gorilla Family & Me’ begins in the UK on BBC Two, Monday 21 December at 21:00 GMT.

Find out more about Chimanuka and the gorillas of Kahuzi-Biega National Park, DR Congo via vEcotourism.org.

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