The Fascinating Lives of Bleeding Heart Monkeys (Part 2) | Nat Geo Live

Spending just a few days and weeks with these monkeys, you start to see their individual personalities start to emerge. Some of them are chatty, some of them are kind of quiet, others are just plain old mean. And while it's interesting to watch this just from a human observer perspective, this is also really valuable information for scientists. By tracking individuals from dawn until dusk, every day, we can take this kind of individual-level information and learn about their structure of their society. Like who's related to whom, who's higher ranking or lower ranking, or bits about if they're stressed out and what that means for their internal state.

Unfortunately, you can't embarrassingly go up to a monkey and ask for a reminder of what its name is if you forget. So we invest a lot of our time in the field just trying to learn their faces. And this involves binoculars, standing really close to something, and just staring at it. For some monkeys, this is not that hard at all. This guy right here is a face that only mother monkey could love. And hopefully, it doesn't reappear in your dreams a little bit later tonight. This one you could learn in five seconds.

Other animals you don't have to rely on faces. Topanga here on the left has half a tail. You can tell her from twenty, thirty meters away. But for the majority of them, it comes down to looking at little ridges in their face, little moles they might have, or old scars from fights. So we try to get as much of this into our own mental banks as we can, but we do rely on our notes. And fortunately, Vivek and I are both world-class natural history illustrators. And we've filled up our notebooks with all sorts of illustrations like this. (laughter) I think this is Vivek's Mona Lisa here. But jokes aside, this is a really valuable tool to kind of remember the little landmarks on a monkey's face.

And so we were the first kind of cohort of camp managers at Guassa. So not only did we have to learn monkeys that had been identified by Peter and Nga, but we also identified a bunch of new ones as well. And on some days, it was really exciting. You see a female who's recognizable, and you might want to name her. And this is what happened with a juvenile, I think back early when we were there. I was just standing there, and Vivek ran up really excitedly.

• [Vivek] Jeff, I have a new monkey for us.

• Oh, really? That's very exciting, Vivek. Have you thought of a name yet?

• I think I wanna name it Anusha.

• Anusha? What does that mean?

• Well, it's my sister's name, and I think she'll hate it. (laughter)

• Perfect. It's decided. Normally we deliberate a long time back and forth cause these names are in the record, but that one was a pretty easy call. And it's been fun to track Anusha over the years. I know she was a juvenile when we first identified her. And now she's come into her own. She has offspring, and some of the latest news is that Anusha has a new male, which is very exciting.

But mothers have really intimate relationships with their infants; they invest a great deal of time with them, caring for them while they still have to go about their daily duties. So you'll see a mother holding an infant like this with one hand, while she's grabbing grass with the other one. It's always amusing when she kind of crosses wires a little bit and is whacking her infant in the head while she's putting grass into her mouth.

But this relationship between mother and infant can last years. As they grow up a bit more, they'll give them rides when they're tired. Geladas can walk several kilometers a day in search of just the right grass meals. And they'll help them jump across little obstacles like this. And when the kids need help, they'll let them know; they'll stand there screaming like (screaming). And then it annoys the mom just enough she'll throw them on the back and take them to the other side.

But it's not only behavior that we focus on while we're out there. Knowing individuals can unlock all sorts of other information sources as well. You can tell Vivek's really excited about this one. I think he gave a little teaser of it earlier. And this is processing a monkey fecal sample. And when a monkey poops, it gives you all sorts of information. It tells you what it's been eating, how well it's been digesting that, and other information about its internal state. You can extract hormones from poop as well.

So what we do is we follow known individuals around and then try to guess when they're going to poop. And Vivek and I are both pretty competitive guys, so this is a nice way to pass those long, endless days in the field. You know who can end up with the most fecal samples in the morning? Like who can have the (bleep)iest morning? I haven't talked about this publicly before, but I think Vivek's a little bit better at this than I am, unfortunately.

So congratulations.

• [Vivek] Thank you.

We can also look at disease in fecal samples. Because disease is an important part of the geladas' ecology. About 30% of adults in the population at Guassa have parasitic swellings of tapeworms from the genus Taenia. And you can see the swelling here on the head of this monkey, but they can be found anywhere on the body. At some point, the swellings will continue to expand and occasionally rupture. And it's a way that the monkeys can get infected and then lead to mortality.

Another kind of outlet of competition for Vivek and I related to disease in us. I lost about 30 pounds of body weight while I was in Guassa my first year. And that had to do with a variety of bacterial and viral issues. But we had this contest running for some reason, that we wanted to know who could go the longest without a shower. So we went for I think two months and then a couple of days, and I was supposed to go back to the capital right before Vivek, so I broke. And I was like, all right fine, this one's yours. But this sort of idiotic competition led to other problems as well.

I think for both of us, the flesh on our hands started rotting off and falling off in big sloughs, and we didn't really know what it was. So we wrote to some tropical disease specialists, and they didn't know what it was either. So we dumped some balsamic vinegar on it, and then we put gloves on, and it went away after a couple of months.

• Okay well. So you just heard about how Jeff and I can get pretty competitive. But that's mostly in very trivial contexts because we had too much time on our hands. But male-male competition in geladas is actually no laughing matter because it has profound life and death consequences. I mentioned earlier how each male gelada is associated with a group of females, his harem. Now this kind of demographic imbalance creates a problem because it means there's this pool of males that aren't getting mating opportunities.

So there's a huge amount of competition for these top spots. And evolution has basically shaped gelada males to reflect this legacy of competition. You can see that in this male here. First of all, he's big and imposing. Male geladas are about twice the size of the females. If you're gonna be fighting all the time, it really helps to be big. And they may look even larger by this billowing cape that you see right here. The secondary sexual characteristic. This makes him look more imposing in these aggressive interactions.

We also go back to the chest patch. So he has a very red bleeding heart there. And what that indicates is that testosterone is coursing through his veins; he's ready to fight and put it all out there. What's truly spectacular, though, are the canines. Gelada canine teeth are one of the largest among any primates relative to body size. And during the day when we're out with the animals, we can hear them grinding their teeth against each other.

They're grinding that canine against the bottom row, sharpening it for subsequent conflict. Now when fights erupt, they can be pretty crazy to watch. And sometimes we even get hit by monkeys that run into us. But they can go on for hours, if not days. And eventually, there's gonna be a winner.

So we observed a days-long interaction in 2011, where at the end of it we heard a bone crunching sound, and one male limped away totally bloody. He disappeared after a few hours, and we never saw him again. All the geladas become really, really upset during these takeover events. But it's the adult females in the group where there's a takeover attempt that stand to lose the most. That's because in geladas, because of the social system they have, you see a very disturbing, distasteful behavior. This is infanticide. The killing of infants.

The way this works is the new males will grab an infant off the mother's back, and it will turn these canines onto the baby. Why are they doing this? They're doing this because that baby isn't theirs, and they wanna have their own chance of reproduction. So by killing this baby that belonged to someone else, they're able to stop the mother from lactating and have her start her cycle again so that he can then mate with her.

So these males are advancing their own reproductive interests at the expense of the females, as well as at the expense of other males like the one you see here. Terrified that his offspring is about to get killed. Now the females in the story are actually not passive players at all. And it was recently discovered that geladas have evolved an amazing strategy to counteract these infanticidal tendencies of the males.

So this was discovered by our colleagues at the University of Michigan, working at the Simian's research site, with geladas in Ethiopia. They discovered that in geladas a phenomenon known as the Bruce effect is operating. What this means is that when there's a takeover in a group, the females who are pregnant will spontaneously terminate their pregnancies. Pregnancy and having a baby is really energetically costly. If that baby were to be born, it would be killed the day that it's born. So they cut their losses and terminate the pregnancy.

They start cycling again and can soon have a baby. In the end, they end up losing little time overall in their own reproductive careers. So this kind of drama, it almost seems more fitting for Game of Thrones, but this is daily life for a gelada.

This can be heavy stuff to watch, particularly when it's your job to just take notes about it or gather pictures of it. But it's part of the job. You sign up for this when you engage in kind of a long-term field project like this. And it also comes with other aspects. When you're out in the field for months at a time, particularly in alpine environments, you're exposed to some very extreme weather that can be challenging as well.

So as we kind of proceed through this day in the life of a gelada, in the early afternoon it can turn from sunny to just absolutely dreadful very quickly. And this has big impacts on our data collection, our ability to take photographs, and our ability to stay sane, which is going to be reflected shortly.

(thunder booming)
(heavy rain falling)

• Just another rainy day. It's been raining about non-stop since 5:45 this morning.
  (heavy rain and hail falling)
  Woah (bleep)!
  (lightning crashing)
  (heavy rainfall)

• [Vivek] You still alive out there?

• [Jeff] Yeah, it's quite a show. What?

• [Vivek] Merry Christmas.

• Yeah, yeah. (laughter)

I think we've spent several Christmases at the Guassa, but it's always Christmas when there's hail on the ground. People ask me sometimes if I'm afraid of the monkeys attacking me or afraid of the animals kind of turning on us out there. But to be totally straight with you, it's the lightning. I am deeply, deeply afraid of lightning in alpine environments. And rightfully so. It's very dangerous.

So I get kind of a chill seeing some of those videos. They're fun to look back on, but I don't want to spend another rainy season at the Guassa. And to be fair, the geladas probably don't wanna spend another rainy season at the Guassa either, but they don't have as much choice as I do. It's a very exposed place; there's nowhere to hide. So they just have to sit out there and take it like your research assistant sitting right there as well.

And they'll bundle together and just wait it out. Some days they won't even come up from their cliff edges. And they can be difficult to find for days or weeks at a time. But with these rainy periods, which can last for days or weeks or months, there's kind of a seasonal cycle to it; the highlands transform. They become very lush.

On the Guassa, the grass grows green and tall. And down on the farms, the crops start growing and the livestock start to fatten up on the really nutritious grass that exists down there. There's more livestock in Ethiopia than in any other country, yet it's rare to see any livestock on the Guassa itself. And this is by design. For centuries, and we're talking hundreds of years here, the local community has limited access to the Guassa, except during an occasional time of need every couple of years.

And what this means is that they're trying to protect their most precious resource on the Guassa. And that's the grass. The word Guassa is derived from the Amharic word for festuca grass, which you see growing here. Aside from being a potential buffer zone for grazing animals and livestock, the grass itself is a very useful resource for the local people. They use it to thatch the roofs of their houses, they use it to build ropes, line their floors, build brooms, and many other tools as well.

And for centuries, enforcement of this closure of the Guassa from grazing or for grass cutting was associated with the Ethiopian Orthodox Church. This is a really important institution in the highlands. And it ties in with traditions that go back more than centuries. Enforcement could be very severe. However, many years ago, if you were caught illegally grazing your cattle, it would be killed on the spot. If you cut grass without permission, your house would be burned down.

In recent years, a more secular and less severe version of this enforcement has emerged, and now it's being led by this man, Admassu Getaneh. Who's a former soldier turned conservationist. He leads patrols of local farmers from the community on the Guassa day and night looking for unwelcome outsiders. People that are poaching its resources, cutting its grass, cutting down its shrubs to make charcoal.

And for centuries, the fact that they've been preserving this region to protect its grass has had the unintended consequence, at least initially, of preserving its wildlife. This is not the case throughout many of the other parts of the Ethiopian highlands, where farming and overgrazing has led to erosion and just the real change in the land cover that you see. This is outside of Guassa, and this is a photograph of Ryan Burke, another former camp manager from the Guassa Gelada Research Project.

Over the past several years, along with several of his Ethiopian colleagues, they've been scouring the highlands looking for information about geladas, censusing them, and figuring out what their distribution is. And they've created this map. This is the most up-to-date understanding that we have of gelada distribution. They're found only in Ethiopia, along these high-altitude ridge lines associated with the Great Rift Valley and the gorges that go inland from it.

This is a much-reduced range from what people thought geladas existed in, based on some preliminary surveys 40-50 years ago. And right now, Ryan and his team are still working on these surveys; there's a couple areas left to go but this is really rewriting what we know about gelada distribution. The Guassa is located right in the center. And it stands apart, as I mentioned, as the most ecologically pristine elements where geladas are found.

And with an ecologically intact environment comes other things. In this case, predators. It's very rare to see a predator out in the daylight in the highlands. This is only one of a couple sightings I had of a serval cat over my time there. But there are also hyenas, leopards, and other mammalian predators in this environment. Despite the fact that you don't often see predators, they still have a massive impact on the behavior of this species.

Geladas are always on edge. And you'll hear alarm calls coming up maybe several times a day, where geladas will stop what they're doing and scan the environment. Devoting all their attention to assessing whether there's a threat in the area. Most of the time these are false alarms. But they have good reason to be worried. I had no idea that I was standing just a couple meters away from a serval that was hiding in this bush.

And neither did the female who was carrying this infant. I was standing there, and I saw a flash of movement, and heard geladas starting to scream. I spun around and kind of threw my camera up and took this photograph. A second later, the serval was gone, buried in this St. John's wort thicket. You can tell this infant's just a couple days old, still has the umbilical cord attached and a dried-out placenta on it. The herd was screaming and fled back towards their sleeping cliffs, followed by their mother, who was giving her own mournful calls.

Even if geladas don't experience a predation event, just seeing a predator is often enough to send the herd fleeing back towards the cliffs.