Chimps take higher ground for strategic advantage

The history books are full of tales of the importance of using elevated terrain in warfare. But new research from the University of Cambridge suggests it’s not just humans who use hills to their advantage in combat. Chimpanzees in West Africa also use high ground to conduct reconnaissance on rival groups before making forays into enemy territory. The study's lead author is the University of Cambridge’s Sylvain Lemoine.

Sylvain - The chimps when they travel in their territory, they have like these movements toward the outskirts, toward the periphery, which is a dangerous area where they can meet hostile neighbours. So by comparing the usage of elevation in both directions, we found out that they're twice more likely to climb the high hills in the overlap area with other groups. And in the periphery when they move toward the periphery than when they come back.

Will - When they do this, how do we know that this is reconnaissance as opposed to them just enjoying being on top of a hill? Is there a difference in their behaviour that you noticed?

Sylvain - So when they are in the periphery at high grounds, they are more likely to adopt quiet activities like resting where individuals are just not making noise. And combined with the previous effect of being more likely to stop at the high hills on the periphery. While if they were going for other purposes, we should not expect a difference between travelling toward the outskirts of the territory and going back. And we should also see no differences in the activities when we compare the periphery and the core area.

Will - When they are at the top of the hill and they are trying to detect other groups of chimpanzees, what senses are they using? Because it's quite hard to spot something in a jungle, isn't it?

Sylvain - Yeah, so these high spots in the field site where we studied chimpanzees, these slopes are, and the top of the hills are, obviously covered with vegetation. So they are not providing particularly good lookout points, but the acoustic conditions, and so the auditive ability to detect long distance calls, is much more improved.

Will - Say that they're at the top of a hill then and they hear a rival group of chimpanzees fairly close by. How does this affect their behaviour going forward?

Sylvain - When the neighbours are close by, the chimpanzees tend to retreat from the hills when they hear them. But they tend to approach the neighbours when those are much further away. And this effect is particularly prominent when they are on the top of the hills. So that makes us conclude that the hills enable further detection of the neighbours.

Will - Every time there's a new study that comes out on chimpanzees, it's remarkable how similar you can imagine this sort of behaviour being compared to early humans. So we watch them manipulate stone tools and there's even speculation as to how long it'll be before certain chimpanzees can manipulate fire, which is a terrifying prospect. But do you think a study like this kind of gives us a window into the past, into our own human evolution?

Sylvain - Yeah, sure. And that's also one of the main reasons why we study one of our closest living relatives, chimpanzees, is that they give us insight on the behaviour that we have in common. And that means behaviour that could have been present in our last common ancestor. So as research goes we discover more and more similarities. But what it tells us about our own evolution is that there are aspects of intelligence, aspects of collective behaviour that are deeply embedded in our evolutionary past. And that can tell us much more about how our ancient Hominins, and species that have disappeared now, could have thrived in a very competitive environment.

Will - Is there a chance then that this sort of behaviour, seeking out high altitude areas for reconnaissance and protection, might have been what put us ahead of the pack when it comes to the rest of hominids?

Sylvain - This is a possibility. There is a body of theories called the Complex Topography Hypothesis that states that when the transition between forest and savannah dwelling, ancient hominids could have used cliffs and plateaus, typical landscape found in East Africa, to thrive in a changing environment. And that could have helped them in hunting strategies but also anti predation strategies, themselves avoiding being eaten by big cats. So then remains another possibility of the usage of this tectonic landscape, which would've been in competition with other groups of the same species or even competition with other human-like creatures in that time. So that remains a possibility. And the importance of high ground in military tactics seen nowadays tells us as well that we have probably kept certain fundamentals of this collective action that take place during warfare.