Zoologger is our weekly column highlighting extraordinary animals – and occasionally other organisms – from around the world

Species: scattered primates, including chacma baboons (Papio ursinus) and ring-tailed lemurs (Lemur catta)

Habitat: limestone caverns and cliffs

They’re not afraid of the dark. A group of chacma baboons in South Africa’s De Hoop Nature Reserve and a group of ring-tailed lemurs in Madagascar have been spotted taking shelter and even sleeping in caves – much as early humans used to do.


For the baboons, it started when the group lost their leader. The charismatic alpha male from a neighbouring territory took over – and brought with him a revolutionary idea.

The troop moved to the new alpha’s home range, near the reserve’s Dronkvlei cave. Then they began to disappear at night.

“They started using that area and we could never find them,” says Peter Henzi of the University of Lethbridge in Alberta, Canada.

Researchers eventually spotted the baboons descending into the cave one evening, bravely following their new leader to an underground sleeping spot.

Spelunking primates

Some early humans also made use of caves, but although colobus monkeys, langurs, chimps and gorillas have been seen entering caves on occasion, this behaviour seems to be rare in modern primates. We used to think this was because early humans had some unique advantages – their mastery of fire making it easy to light the way, for example.

But the baboons don’t need to light their way to the sleeping spot, some 5 metres down a narrow shaft then across a 40 metre passage in pitch-blackness. Instead, they keep in touch with each other through calls and grunts.

It’s no walk in the park – one newcomer to the group refused to enter the cave for two weeks – and the South African caves are not free of danger. During Henzi’s study a leopard haunted a nearby cavern, and a Cape cobra lived in the cave system.

But ultimately, the benefits may outweigh the risk. The cave offers protection from other predators and the temperatures within stay stable through cold winter nights as well as summer heat waves.

Hide and seek

Another group of primate have also figured out the benefit.

In Madagascar’s Tsimanampetsotsa National Park, Michelle Sauther from the University of Colorado Boulder was surprised to find the ring-tailed lemurs she studied appear as if by magic in the mornings.

“We heard movement along the limestone face,” she says. “Once the sun came up we realised there were these numerous small caves.”

For these ring-tailed lemurs, small overhangs in the limestone cliff face offer sleeping spots that their predators, cat-like fossa, can’t reach.

The danger in this case it that switching from the trees to the cliff brings lemurs briefly low to the ground, making them vulnerable to fossa. “Getting up and going to bed were clearly the most dangerous periods for them,” Sauther says. “They needed to literally scale this vertical rock face, much like little furry rock climbers.”

Just like us?

To both Henzi and Sauther, continued loyalty to caves shows a behavioural flexibility that may run deeper in our primate lineage than we realised. For animals that need to balance the demands of group living with reliable shelter, caves seem to be worth the risk – even without fire and light.

Henzi thinks such a basic, elemental use for caves might even help explain the recent discovery of hominids in the Dinaledi cavern in South Africa.

H. naledi have been hailed as the newest species of humans: bones belonging to 15 individuals were found deep inside a dark chamber, some 80 metres from the entrance. What was such a big group doing so deep inside a cave?

The authors controversially speculated that the chamber represents a burial site. More recently, some have even suggested it was a homicide site.

But judging by the chacma baboons and the ring-tailed lemurs, the explanation might be much simpler. “It seems more parsimonious to argue that they were using the caves because it was a comfortable place to stay,” Henzi says. The jury is still out.

Meanwhile, Sauther’s former student Marni LaFleur continues to study the lemurs – we may not have heard the last word on cave-dwelling primates just yet.

Journal reference: Journal of Human Evolution, DOI: 10.1016/j.jhevol.2003.11.005; Madagascar Conservation and Development, DOI: 10.4314/mcd.v8i2.5

Read more: “Prehistoric cinema: A silver screen on the cave wall”

Image credit: Marni LaFleur/bloglafleur.blogspot.co.uk/