Gorillas need their space

17 March 2020

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Gorillas were previously thought to roam widely and mingle freely. But a new study in Scientific Reports done in the Republic of Congo suggests that groups of gorillas actually get territorial, although in a gentle way that hints at parts of our own human nature. While their relatives the chimpanzees get pretty violent over personal space, gorillas seem to take a more gradual approach - much like you might invite an acquaintance into your sitting room, but get annoyed if they start poking around in the upstairs closet. Phil Sansom spoke to the lead author, Cambridge University’s Robin Morrison…

Robin - We found that gorilla groups are avoiding their neighbours, and they do this by avoiding their neighbour's home range. They seem to have at least some level of awareness of where their neighbours' home ranges are and they then avoid those areas.

Phil - Is that surprising? I mean, did you not expect gorillas to have this kind of territory?

Robin - We suspected it maybe, but it's something that's not been seen in the past. Gorillas are quite different to a lot of other apes in that they have tolerant interactions with their neighbours quite often. So you can even see multiple groups feeding quite happily in the same tree together without a lot of aggression going on. For those reasons it seemed a bit unusual, but actually what we're thinking is maybe it's a lot more similar to what we see in humans, where we have our personal space but then there are also public areas where we'll interact quite friendli-ly.

Phil - Tell me about these gorillas that you studied. Where are they?

Robin - In Republic of Congo. So it's Western lowland gorillas. And one of the reasons we're particularly excited about this project is it's really hard to study them. So they can take about five years to become used to humans, and so there's a really small number of groups that are habituated to human presence. And so this is why we needed to monitor them remotely, so that essentially they wouldn't run away from us and we could record what they were doing when there were no humans around.

Phil - Is this way out into an area that's not populated by humans at all?

Robin - About 15 kilometres from the nearest village. From there on out it gets quite remote. So sometimes we'd be out camping in the middle of rainforest where there were no humans and no access to anything like electricity, or running water, or a house. Quite exciting!

Phil - And how are you actually keeping track of them if you don't want them to run away and get scared of you?

Robin - We had kind of a network of these camera traps out all over the forest. So these are motion-activated cameras. Not like any sort of physical trap, it's a motion-activated camera.

Phil - Not a bear trap that's got a camera on?

Robin - Yeah, non-invasive, absolutely no harm to the gorillas.

Phil - How many groups and how many gorillas?

Robin - Oof, what a question. It was about 50 kilometres square total, and we got good data on about eight different groups. And so this was just over a hundred different gorillas.

Phil - Now how do you even keep track of a hundred different gorillas? Because call me ignorant but gorillas mostly look the same to me.

Robin - Yes, it's very difficult I would say. I'm okay at recognising gorillas, but when it comes to recognising whether a gorilla you've never seen is one that maybe you saw once? That's pretty difficult. So we use the shapes of their faces, and especially patterns around their noses and their brow ridges, to distinguish between them. There's been some developments in AI, but actually right now when we did this study, what we found is that humans were still better than machines at recognising gorillas. It just took some very skilled people!

Phil - And is this where you started to see these patterns?

Robin - Yes, yeah. So we gradually built up this database of, "okay, this gorilla was here on this day, and then they moved over here, and then they moved over here." They would very rarely turn up in the same camera on the same day as another group, so it seemed to be that they were avoiding each other. Also, the deeper into another group's home range they got, the less likely they were to turn up.

Phil - Did all the groups do the same thing?

Robin - It's hard to say from our analysis, but more from personal experience of following certain groups we do see that there are groups that they seem to hang out more with.

Phil - Oh, so you did actually follow some groups out in the wild?

Robin - That's not part of this study, but we also do. So there's three groups in that area that we follow daily.

Phil - Were there any gorillas that you gave names to or bonded with?

Robin - Yes, yeah, of course. I mean it's hard to study gorillas and not become attached. And for me, I spent about six months following this group, and there was one gorilla that was kind of a young male that they called Robigus. He was the only one that wouldn't run away from me, and so gradually we'd get to know this family. So her for me is my all-time favourite gorilla.

Phil - How do you spell that?

Robin - R O B I G U S.

Phil - Ah, sort of like your name!

Robin - My boss chose to name him after me, to some extent, because he seemed to be particularly friendly towards me.

Phil - Now when it came to the groups that were avoiding each other, you said at the start this might say something about the way we humans behave. Can you explain that?

Robin - Yes. Often when we're trying to understand human behaviour we're comparing that with our close evolutionary relatives; so the chimpanzees, gorillas, orangutans. Chimpanzees are extremely territorial and they can even be very violent defending these territories. And some people have suggested that this might show where kind of the evolutionary origins of human warfare come from. But in contrast these gorillas show a much more gradual defence of space, much more tolerance in some areas and aggression in others. And so this could potentially show commonalities with humans where we can be quite aggressive sometimes, but also have these long term affiliative relationships between different groups. And these are really important for helping us understand large scale cooperation, which is really important to the human species. It's one of our fundamental behaviours.

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