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Chasing Orangutans

Andrea DiGiorgio explores what big primates eat and why we should care

During the summer months, we are revisiting some of our favorite BU Today articles from the past year. This week, we feature stories first published on BU’s Research website.

Andrea DiGiorgio—former corporate saleswoman, current Boston University PhD candidate—is going to spend 2015 chasing orangutans through the jungles of Borneo, gathering samples of their food. (Who said science isn’t fun?) Funded by a three-year graduate research fellowship from the National Science Foundation, DiGiorgio’s goal is to learn more about primates by studying what they eat. Orangutans are endangered and may go extinct in a few decades. Understanding their diets may lead to better conservation strategies. She also hopes to gain understanding about the current human obesity epidemic. “Looking at our closest relatives, the other great apes, will provide insight as to what we evolved to eat,” she says, “and whether this ancestral diet is mismatched with our current diet.”

Collecting orangutan food is not easy. Not only will DiGiorgio need to run through the jungle and catch falling fruit, she will also have to climb 100-foot-tall trees, a skill she learned at the Cornell Tree Climbing Institute in Ithaca, N.Y. (See the video above.)

DiGiorgio spoke with BU Today about the joy of switching careers, the mystery of bark-eating orangutans, and why she’s the best person to call if there’s a zombie apocalypse.

Andrea DiGiorgio, BU PhD, Borneo

Andrea DiGiorgio, BU PhD candidate in biological anthropology, will spend a year in Borneo studying what orangutans eat. Photo by Cydney Scott

BU Today: You used to be in sales before becoming a primatologist. How did that happen?

DiGiorgio: I needed a job. I was working in hotels over the summers while I was in college, and I went back to work for management, and that brought me into corporate sales, and I just stayed. It seemed like a lucrative and responsible thing to do. My father is an immigrant from Italy, and so saying, “I want to get a PhD and go around following primates,” or any of the other crazy ideas I had back then, would not have been the smartest thing to do. So I jumped into sales. I never liked it. And I ended up getting laid off one day.

Sounds like the best layoff ever.

Yeah. And I decided that day that I was probably going to have to take another job in sales, but that I was going to work toward what I really wanted to do. I was going to think about anything that I could possibly do so that I could work happily for the rest of my life. And this is what I came to.

Why did you want to study primates? Did you see a nature documentary when you were a kid?

I wish it were that simple, but no. I just have always been really interested in primates; they’ve just always fascinated me.

How did you end up with orangutans? I’d think most people would go for the chimps and bonobos.

That’s what you’d think at first. When I was working full-time in sales, I volunteered on weekends at a zoo, working with chimps. And for some people, working with chimps is probably the easiest way to decide that you don’t want to.

Why? They’re so cute.

They are very cute on television. They’re not my favorite primate anymore. They’re just too similar to humans, in a way, for me. It almost demystifies them. They’re amazingly brilliant, and always one step ahead of you in captivity. But they just didn’t spark my interest as much as working with other primates. Lemurs, gorillas, orangutans were the three groups I really wanted to study. At the zoo, I got to work with the lemurs, and really started to like them.

Lemurs seem really boring. They just look like squirrels with raccoon tails.

The lemurs’ evolutionary history is amazing—and the diversity.

“You can’t dissociate the environment from the animal. How an animal learns to deal with its environment is such a major part of their evolution.”

OK. So how did you end up with orangutans?

My advisor, Cheryl Knott, a College of Arts & Sciences anthropology professor, had a phenomenal project going on, studying orangutan behavior at the Cabang Panti Research Station in Gunung Palung National Park in Indonesia. And orangutans have a very interesting diet, so given that I wanted to study habitat use and diet, they are a great primate to research.

Why do habitat and diet interest you?

You can’t dissociate the environment from the animal. How an animal learns to deal with its environment is such a major part of their evolution. Understanding how they get food, what size they can grow to based on the food that’s available and the space that they have, is just fascinating to me.

What do they eat?

Overall, orangutans are viewed as frugivores, animals that eat fruit. When fruit is available, orangutans will eat it. And that’s how they’ve been studied, and fruit has been a major focus. But they also eat leaves and bark. And the leaves make sense to me because they are high protein, and orangutans are big enough that they can probably digest them well enough. But it seems as though leaves are a better choice than bark.

Are they eating bugs in the bark?

There are termites and ants that they eat too, but we don’t see them eating those as much. They eat this type of pith from within a tree—if you peel back the outer layer of the bark, it’s the inside. Why are they doing that? Why not stay with something that’s high sugar, high energy? I wanted to understand why they eat these other things when fruit is available, why they don’t just stick with fruit. From a human perspective, I think it makes sense because we have different cravings for things, and we don’t want to just eat fruit or sweets all day. But since we can’t ask them, “Did you just crave something else?” I want to look specifically at nutrients and what they’re going after.

Orangutan, Eating, Leaves

Orangutans get most of their calories from fruit, sometimes up to 10,000 calories a day. Photo by Tim Laman

Maybe they just need a little something crunchy.

Exactly. If you’re in a forest without potato chips, what do you do?

But what do you think? Are they going after a mineral or something?

It could be. I tasted what they dropped that day, and it kind of tasted fatty and salty. And so I really want to do some salt analyses.

Maybe this is where all our diet problems started.

Right, the craving for sweets and salt, yes. Salt makes sense in forests too, and a lot of animals do seek salt. But I don’t think it’s just salt. I think it’s going to be a very complex picture. They try to eat as many calories as they can. They want to put on as much weight as they can whenever the opportunity comes around. And it seems like a lot of humans try to do the same.

Yes, I’m awesome at eating lots of calories and putting on weight.

We’re all so well evolved. But overall, I think they’re probably going to be trying to get x amount of protein during the day, which you may not be able to get from fruits.

Do you think they might get it from the bark?

So far, we don’t know. We need to analyze more bark samples, which is why I want to go over there and get hundreds to thousands of food samples.

How do you get thousands of food samples?

You get up usually around three or four in the morning, try to leave camp by four or five. And you go back to where the animal had built a nest the night before. And so you’re walking through the dark in the rain forest, and it’s an unbelievable experience. And then you literally end up following thread, because the team has marked a path to the nest, from the closest trail marker. So you find the thread, and you run your hand along it through the forest until you get to the tree.

And then you sit and wait for the animal to wake up. You hope it’s after daylight, because you can lose them very easily if it’s still dark. And then you just follow them throughout the day. When they stop and eat, you write down everything that you can see that they’re eating, and you try to get a rate of how much is going into their mouth. And if they drop samples (which happens quite a bit), you can get samples that way, because they will be from the same part of the tree. The next day, I—or the two tree climbers—will go back and try to collect whatever food I couldn’t get.

Tree Climbing, Andrea DiGiorgio

One of the toughest parts of tree climbing is setting ropes. DiGiorgio says it could take one to five hours to set ropes in the trees in Borneo. Photo by Cydney Scott

This is why you learned how to climb trees?


Are the trees in Borneo going to be a lot more difficult to climb than the ones in Ithaca?

Yes. In Ithaca, they’ve picked trees for different reasons. The teacher knows which trees are safe to climb, because he’s investigated them. In the forest in Indonesia, you not only have a larger, taller, uninvestigated tree, but also lianas [vines] and other trees growing around them. And so just setting the rope is going to take between one hour and five hours.

Five hours to get a rope into the tree?

Yeah, to get a rope into the tree. I’m learning archery, because I need to be able to shoot arrows into the trees to get the rope in.

You’re building an awesome résumé.

If there’s any type of natural disaster, any zombie apocalypse, I’m your go-to.

What are you going to do with all the food you collect?

We bring it back to camp, and I work with an assistant on pulling out the parts that the orangutan ate, and then drying them in a kerosene drying oven. Some of it will go to a lab in Indonesia, and the rest of it will come back here for analysis. I’ll be looking at protein, carbs and overall calories, fats, and anti-feedants—those are chemicals that impede nutrient digestion or have toxic effects.

What kind of fruit do they have in Borneo?

It’s nothing that you can imagine really, other than durian. They’re not high quality. Approximately 40 percent of the orangutan’s diet is fiber.

They must just spend all day eating.

They do. Apes can chew for around eight hours a day.

Do you know how many calories they need?

We don’t know exactly how many they need. We think the females need probably around 1,800 to 2,400 calories a day, and the males need around 2,400 to 3,000 calories. But you will see days where they’re eating more than 10,000 calories, during high fruit periods.

It seems impossible to get 10,000 calories of fruit.

I know. I could do it with ice cream, no problem. But fruit, I would have trouble with. I might even have trouble with ice cream, and that’s an easy one for me.

Orangutans are endangered and may go extinct in a few decades. Understanding their diets may lead to better conservation strategies.

So what will all this information help us understand?

We study nonhuman primates for several reasons. One of them is to understand the evolution of humans. And orangutans are interesting because they’re the only other great ape that left Africa to live in these unpredictable rain forests. Part of what they’re doing, I think, is looking for protein. If we find that orangutans do prioritize protein, that’s the same thing that humans do, we think, whereas gorillas seem to prioritize calories. They try to get a certain number of calories.

But I also want to work towards conservation. I’m interested in primates just for the sake of primates. We say orangutans are frugivores and they eat certain fruits most often. But if we only conserve fruit trees, and they actually need other resources—like the bark—then even though we conserve what they eat most often, we may be inadvertently depriving them of something that they need. So I want to find that out. I want to see if they need protein, I want to see if they need fats, so that we can start determining the types of trees and the types of habitats that are best to conserve.

I feel very lucky to get to study orangutans, especially given that there aren’t that many of them left. Right now, there are probably fewer than 70,000 Bornean orangutans in the wild, and I hope to be part of their survival. Orangutans are attractive and familiar to people, and by preserving the forest for them, we also preserve the forest for the trees, insects, plants, and other less engaging flora and fauna. It is amazing to get to study them, and hopefully be a part of their conservation.

A version of this story originally appeared on BU Research.


4 Comments on Chasing Orangutans

  • BU staffer on 01.26.2015 at 9:48 am

    Great article/video! I enjoyed that this piece was both informative and had a sense of humor.

  • Yang on 01.27.2015 at 2:16 pm

    wonderful!Good job!

  • Ellie on 01.27.2015 at 6:06 pm

    Andrea was an awesome anthropology teacher!! I really enjoyed being in her class.

  • Hari on 01.27.2015 at 9:22 pm

    I am from Indonesia, if Andrea needs a crash course on anything about Indonesia or about the Indonesian language I’d be happy to help her or put her in contact with other Indonesians. Feel free to contact me.

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