Earthquake on Chimp Mountain

It had been a long day in the field and we were all exhausted. I crawled into bed amid a thunderstorm and listened to the loud claps of thunder and the rushing sound of rain falling on the ground outside. I started to doze as the thunder gradually softened and the rain turned to light drizzle. Abruptly, I was jarred awake by the harsh and unmistakable vibrations of an earthquake. We ran outside and waited another 30 seconds or so until it passed. Everything seemed fine. No major damage, but people yelled loudly from the nearby village as monkeys gave loud alarm calls. This earthquake was the second in as many days. The first measured magnitude 5.2. This one felt quite a bit stronger, measuring magnitude 5.7. We had a restless night, with aftershocks as strong as magnitude 5.4 occurring frequently throughout the night. Seismic activity is not uncommon in this area. Western Uganda lies along the Albertine Rift, an active area of tectonic shifts that are slowly separating the Somali Plate in East Africa from the rest of the continent. The earthquakes we’ve experienced in the past week have had their epicenter along the rift in Lake Albert to the west.On our way to the field the next morning, we were all a bit bleary-eyed, but the earthquake was an animated topic of conversation among all. Amid our discussions of how our Ugandan friends responded to the event, I wondered how the chimpanzees in the region fared as well. Ethologists and others have written numerous articles regarding how animal behavior changes preceding and during seismic activity (e.g., Buskirk et al. 1981; Shaw 1977). Most of these accounts have come from captive animals. For example, in 2011 the National Zoo described the responses of various animals to an earthquake of magnitude 5.8 in the Washington, DC area. Orangutans and western lowland gorillas were among the zoo inhabitants to respond to the quake, with members of both species climbing higher in their enclosures and vocalizing.
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What about free-living primates? Snarr (2005) similarly reported that wild mantled howler monkeys (Alouatta palliata) responded to an earthquake by vocalizing and climbing higher in the trees. Fujimoto and Hanamura (2008) provided a rare account of wild chimpanzee responses during a strong earthquake and its aftershocks in the Mahale Mountains, Tanzania. The chimpanzees vocalized loudly (but were not visually observed) during the main quake. During aftershocks, they typically responded by climbing higher or by interrupting their activities. Interestingly, one female was observed to climb down and touch the ground with her hand, as though to explore the vibrations she was feeling from the ground. Few other accounts exist regarding the behavior of wild non-human primates in response to earthquakes, however.
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When we arrived in the field, we met with two farmers who gave us their own account of the previous night’s events. They were tending an evening fire at their small hut at the garden’s edge.  The garden is situated on a steep hillside in a mountainous rural area. There is a small forest patch near the garden, and the farmers knew chimpanzees were nesting there. When they began to feel the tremors, they also heard the screams of chimpanzees. The vocalizations quickly grew nearer, and soon they saw an estimated 20 chimpanzees in the garden outside their hut. Amid their surprise, they grew concerned that the chimpanzees had run out of the forest to attack them in response to the quake. They banged their machetes on rocks to intimidate the chimps, who went running back into the forest.
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When the farmers awoke in the early morning hours, the chimpanzees called from another patch of forest about 300 meters away. The men were surprised that the chimpanzees seemed to have moved their nests in the middle of the night. Perhaps this shift was related to the strong aftershocks during the night.
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Because we weren’t there, we have no way of confirming whether their account of events is entirely true. However, everything else they told us—the locations of nests, what the chimps had been feeding on, and where they went in the morning—was borne out by the evidence we later found. In short, I have no reason to suspect that their account is anything other than accurate.
What can we make of this account? If chimpanzees did climb down from the trees and leave the forest as the farmers said, this would contrast sharply with Fujimoto and Hanamura’s account of chimpanzee responses to seismic activity.  Indeed, most accounts of responses by captive and free-living primates indicate that climbing up is a more likely response. Perhaps, though, there are reasons why climbing down would be more sensible for these chimpanzees. First, their remaining forest is small and degraded, and surviving nesting trees may be much smaller than those seen elsewhere. Smaller trees may move more and provide less stability during seismic events, making them a less secure option than the ground. The frequent felling of trees in this area may also make chimpanzees particularly wary of the possibility of a tree falling during seemingly dangerous situations. In addition, there are no large carnivores like leopards here, as have been reported the Mahale Mountains, so perhaps moving to the ground at night is perceived as less dangerous. Unfortunately, the paucity of observations of such events makes it difficult to observe these responses and clarify their meanings. Nonetheless, it is fascinating to consider how chimpanzees, humans, and our ancestors may have responded to seismic activity over the course of evolutionary history.
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Buskirk, R., Frohlich, C., Latham, G. (1981). Unusual animal behavior before earthquakes: a review of possible sensory mechanisms. Rev Geophys Space Phys, 19, 247 – 270.

Fujimoto, M., Hanamura, S. (2008). Responses of wild chimpanzees (Pan troglodytes schweinfurthii) toward seismic aftershocks in the Mahale Mountains National Park, Tanzania. Primates, 49, 73 – 76.

Shaw, E. (1977). Can animals anticipate earthquakes? Nat Hist, 83, 14 – 20.

Snarr, K. (2005). Seismic activity response as observed in mantled howlers (Aloutta palliata), Cuero y Salado Wildlife Refuge, Honduras. Primates, 46, 281 – 285.

 This post was originally published at Scientific American


Hunting for Answers

We recently embarked on data collection in a new community of chimpanzees. They were new to us, that is, though we had heard a great deal about them. We heard from local friends that this is a large community, consisting of more chimpanzees than other communities nearby. We heard that they come into conflict with embittered human neighbors more often than anywhere else we have been. We also heard that these chimpanzees are “very tough,” killing goats with fierce slaps, surrounding and killing an antelope, and beating a python to death by hitting it against a tree. They were a fearsome group, as the stories went.

While heading to the forest on our first day of data collection there, I couldn’t help but wonder what we would find. Though the tales loomed large, I expected these chimpanzees to be more or less like the others we’ve observed. After all, they live only a few miles from neighboring communities, and by now, we feel like seasoned visitors to chimpanzees in the region. It’s as though we are houseguests who crash on the sofa for a few days, getting a glimpse into the lives of our hosts before moving on to the next place, never overstaying our welcome too long. After so many miles traveled, so many glimpses into chimpanzee lives, we are not easily surprised.

Our first few days of data collection were productive but not extraordinary. The chimpanzees were gathered in a large party, making them relatively simple to locate. We collected many dung samples easily. After a few days, Emily, a volunteer for my project, asked for some help while washing a dung sample for diet analysis. What, she asked, was the strange-looking stuff in this sample? Upon closer inspection, I realized what we were scrutinizing: the hand of a black-and-white colobus monkey (Colobus guereza). The delicate skin, hand bones, fingernails, and hair were all visible. The evidence was gruesome but clear: The chimpanzee who produced the sample had eaten part of a colobus monkey.

For chimpanzees across studied sites in Africa, animal protein—including meat, insects, and eggs—comprises a small proportion of the diet, typically around 8 – 10% overall (Goodall 1986).  Red colobus monkeys (Procolobus spp.) are the favored prey animal for chimpanzees where the two species overlap. In our study region, there are no red colobus monkeys. Instead, chimpanzees consume black-and-white colobus monkeys among several other species in the nearby Budongo Forest (Newton-Fisher et al. 2002; Reynolds 2005). Black-and-white colobus hunting has also been reported at the Kasokwa Forest, a forest fragment just to the south of the Budongo Forest (Reynolds 2005). As research volunteers in 2007, Jack and I even observed chimpanzees hunting and eating a black-and-white colobus monkey in Kasokwa.

Despite known instances of hunting at Kasokwa, however, little evidence to date has shown extensive hunting by other chimpanzees in this fragmented forest region. Although my colleague Matt McLennan has analyzed the dietary components of over 2,000 chimpanzee dung samples at nearby Bulindi, he has never found evidence of colobus consumption (pers. comm.). My analyses so far have similarly yielded a dearth of animal protein in the diet.

Now, however, we had our first clear evidence of meat consumption. The next day, we watched as a party of chimpanzees fed in a Pseudospondias microcarpa tree, a common tree that produces fruits enjoyed by chimpanzees among other species. After the chimpanzees left, we searched for dung samples beneath the tree. As we looked, Nick told us he had just seen a female chimpanzee in a nearby Psuedospondias tree. We took a closer look and found the lone female sitting calmly and eating a young black-and-white colobus monkey. We watched in utter fascination for thirty minutes or more as she slowly consumed the carcass, taking intermittent bites of leaves between bits of meat. This “steak with salad” style of meat consumption is a commonly observed dining practice among chimpanzees, and may aid in the processing of raw meat. As we watched her eat, we wondered how she came to have this prized catch. Hunting is usually a group activity and a male-dominated affair among chimpanzees (Stanford et al. 1994). High-ranking males often come away with the best chunks of meat, which they may share with persistent community members who pester them until they give in and share their spoils.

How did this lone female end up with an entire monkey, then? Did she take advantage of an opportunity to snatch a young monkey on her own? If so, were the other members of her party still nearby in the neighboring Pseudospondias tree when she went in for the kill, or did she stay behind after the others left to opportunistically hunt? Alternatively, did another hunter share the meat with her?

The next day, we observed yet another instance of hunting. It was morning, and we had just arrived to hear choruses of excited vocalizations along with the throaty calls of black-and-white colobus monkeys. We strained to watch from a distance as they leapt between trees. Nick had the perfect view to see the culmination of their efforts. Three adult chimpanzees surrounded a colobus. One chimpanzee stayed low in the tree while the other two cornered it from above. Then, one of them reached out and grabbed the monkey. We observed as they divided their prey and proceeded to feast on it.

We now had evidence of three hunting instances in one week. This series of events left us with us with more questions than answers. Did we catch this community during a particularly active period of hunting? Hunting rates in chimpanzees are known to fluctuate based on a variety of factors including party size, food availability, and the presence of estrus females (e.g., Gilby and Wrangham 2007; Mitani and Watts 2001; Stanford et al. 1994).  Another question, not mutually exclusive, is whether these chimpanzees are simply more apt to hunt than other nearby communities. Does something about the community composition (e.g., the presence of numerous males) favor a “culture of hunting”? Did the environment somehow promote more hunting opportunities? For example, might the density of black-and-white colobus monkeys be particularly high in this forest fragment, leading to more hunting opportunities? For now, answers elude us. Instead, the questions propel us forward in anticipation of what the next field day might bring among these “very tough” chimpanzees.


Gilby, I. C., Wrangham, R. W. (2007). Risk-prone hunting by chimpanzees (Pan troglodytes schweinfurthii) increases during periods of high diet quality. Behavioral Ecology and Sociobiology, 61, 1771 – 1779.

Goodall, J. (1986). The chimpanzees of Gombe: patterns of behaviour. Cambridge, MA: Harvard University Press.

Mitani, J. C., Watts, D. P. (2001). Why do chimpanzees hunt and share meat? Animal Behaviour, 61, 915 – 924.

Newton-Fisher, N. E., Notman, H., Reynolds, V. (2002.) Hunting of mammalian prey by Budongo Forest chimpanzees. Folia Primatologica 73, 281 – 283.

Reynolds, V. (2005). The chimpanzees of the Budongo Forest: ecology, behaviour, and conservation. New York: Oxford University Press.

Stanford, C. B., Wallis, J., Mpongo, E., Goodall, J. (1994). Hunting decisions in wild chimpanzees. Behaviour, 131, 1 – 18.

This post was originally published at Scientific American




Their chorus of pant hoots gave them away in dramatic fashion. The chimpanzees we’d been looking for were nearby, and we knew exactly where to find them. Though farmland and trees blocked our view, we could hear that the chimpanzees had arrived at a particular fig tree laden with ripe fruits. As ripe fruit specialists, chimpanzees seek out fruiting figs like this Ficus exasperata. On a good day, we can use our knowledge of when these figs are ripening to help us find the chimpanzees.

We took a circuitous route through the gardens to a grassy hilltop with a clear, albeit distant, view of the Ficus.  I dropped my backpack and pulled out my binoculars. I began to scan the tree in an attempt to identify the large dark figures foraging. I could make out the silhouettes of at least seven or eight chimpanzees, all foraging on figs or seated in the huge tree.

Chimpanzees feed in a Ficus exasperata tree. Photo: Jack Lester.


After observing their foraging for a few peaceful moments, I heard a jarring but familiar sound. A man working in a garden nearby shouted at the chimpanzees. Though the tree was in an isolated area of grassland several dozen meters from where he worked, he was clearly uncomfortable with their presence. A few threatening shouts were enough to convince the chimpanzees it was best to cut short their breakfast. They descended quickly from the fig. I now counted twelve chimpanzees as they walked in a single file line back across the grassland and to a small patch of forest nearby. As we watched them go, field assistant Nick commented that he felt sorry for the chimps. At times like these, I am reminded of one of the most recurrent lessons from my research thus far: chimpanzees are surprisingly resilient. They may have waited until later to forage, or perhaps they found another source of nutrition (which, unfortunately, may have involved risky crop-raiding). However, as long as no one hunted them or set a mantrap to ensnare them, as is sometimes the case, they probably found something to eat and survived another day. Despite the rapid rate of forest degradation in their habitat, they have persisted. They continue to forage, reproduce, and tend to the complex political matters of chimpanzee life, even if these behaviors must be modified somewhat to fit a drastically altered environment.

I was again reminded of chimpanzee resilience when, on a recent visit to my mother’s home, I opened an old box to find my childhood collection of troll dolls. After a moment’s consideration, I decided to send them to a chimpanzee named Foxie. Foxie is a resident of Chimpanzee Sanctuary Northwest (CSNW), a sanctuary in Cle Elum, Washington that serves as home to seven chimpanzees. The “Cle Elum Seven,” as they are known, have lived in biomedical laboratories for most of their lives. They were involved in invasive hepatitis vaccine research and used for laboratory breeding. Foxie gave birth to five infants, but was forced to give them all up, just like so many other breeding female chimpanzees in laboratories. Perhaps as a fulfillment of the maternal behaviors she was never able to express, Foxie can now usually be found carrying a troll or other doll with her.

Foxie cares for a troll doll. Photo courtesy Chimpanzee Sanctuary Northwest, used with permission.

Foxie cares for a troll doll. Photo courtesy Chimpanzee Sanctuary Northwest, used with permission.









The caregivers who know Foxie and the other members of the Cle Elum Seven can attest to this adaptability. All seven have displayed drastic changes in both behavior and physical appearance since arriving at CSNW several years ago. The shift from a windowless laboratory basement to a spacious sanctuary with dedicated caregivers and outdoor access has—not surprisingly—had an unambiguously positive effect on them.

Why might chimpanzees be so adaptable to change?  It may have aided the survival of their ancestors–and ours. For example, many primates regularly face drastic seasonal changes in rainfall, temperature, and food availability. Some primates have specialized adaptations that help them survive under harshly changing seasonal conditions. For chimpanzees, a learned knowledge of the fruit tree locations, even during periods of low fruit availability, is critical. Chimpanzees acquire this knowledge over a prolonged period of development, with high reliance on their mothers until full weaning at age 5, followed by juvenile and sub-adulthood learning periods lasting until age 15. A high degree of neural plasticity facilitates this learning ability. In humans, an especially high degree of plasticity may aid our strong reliance on learning. Plasticity may also play a key role in what we call resilience, enabling both humans and our chimpanzee kin to roll with the punches during trying times. For chimpanzees today, this may mean finding a new fruit tree when one due to ripen has been felled, or basking in the sun for the first time after decades inside a laboratory.

This post was originally published at Scientific American.

Uganda’s Other Great Apes

Recently, a dear friend came to visit us here in Uganda, so we decided to take the opportunity to visit Bwindi Impenetrable National Park, home to one of the world’s only two populations of mountain gorillas (Gorilla berengei berengei). The other population lives in the Virunga Massif, a volcanic range that straddles Uganda, Rwanda, and the Democratic Republic of Congo. There are only an estimated 880 mountain gorillas in the world, making them a critically endangered species. Threats such as habitat loss, political instability, and disease transmission have the power to wipe out these fragile remaining populations. Like chimpanzees, gorillas are very closely related to humans and can easily catch the illnesses we carry. Just one outbreak of a respiratory infection could be enough to wipe out an entire gorilla group, or worse.

Though this may seem like a bleak state of affairs, mountain gorillas are actually heralded as a conservation success story. Their numbers have increased significantly in recent decades as a result of conservation efforts linked to ecotourism. Tourists flock to Uganda each year to visit these famous residents. Now it was our turn.

The drive to Bwindi Impenetrable National Park was convincing evidence that this whole gorilla-tracking thing is not for the faint of heart. We crawled along muddy roads with steep drop-offs as we inched higher and higher into the mountains. Each hairpin turn revealed a new, breathtakingly beautiful view of the landscape. When we finally arrived at our camp, we were greeted by staggering views of Bwindi and the nearby Virunga Volcanoes, shrouded though they were in a chilly evening mist. We settled in with hot tea and dinner before heading to bed early in anticipation of gorilla tracking the next morning. Soon after going to bed, rain began tapping heavily on our tents. A downpour continued through the night. By morning, it trailed off to a drizzle as we excitedly ate breakfast and checked to make sure we were ready to go.

View of Bwindi Impenetrable National Park. Photo: Maureen McCarthy.









As we went on our way, our guide informed us that we would receive information on the gorilla group’s location from trackers who had set out early in the morning to find the group. Not long after beginning our trek, which began along a village trail shared with local residents, we received word that the gorillas were not very far off. Indeed, as it turned out, they were less than an hour’s hike away in an area outside the national park. Of course, gorillas don’t recognize national park boundaries the way we do, so it’s not uncommon to find them ranging beyond its borders. It began to look like we wouldn’t be hiking through dense forest at all.We set off in a group of eight tourists. Group sizes are limited to this maximum number in an effort to minimize stress to the gorillas. We weren’t quite sure what to expect. We heard that this trek was so difficult that people often had to be carried out on stretchers. This wasn’t just Bwindi legend. The day prior, a man was carried out of the forest on a stretcher because he was ill and the hiking proved to be too much. As we walked through the village, we saw children carrying another child in a wheelbarrow. Our Ugandan friend explained that they were imitating carrying a mzungu (white person) out on a stretcher. One of the local lodges even has a sculpture in the sitting room depicting the same scene. Just how difficult would our hike into this so-called “Impenetrable Forest” be?

As we hiked down a steep path through uncultivated hillside, we suddenly saw their hairy black figures emerge from the mist. Though I study our nonhuman primate relatives, I still have moments of awe and giddiness from time to time in their presence. This was definitely one of those moments. As we observed them, our guide informed us of the names of each of the gorillas. We eventually saw the entire group of fourteen. Gorillas live in relatively small groups consisting of a single or a few adult males, a number of females, and offspring. This is in stark contrast to chimpanzees, which live in fission-fusion communities consisting of anywhere from 20 to over 180 individuals.

We watched and followed them for one hour as they fed on leaves and dead wood, foraging slowly and relaxing. They were absolutely fascinating and majestic, and their habitat was absurdly beautiful and rugged. I marveled at it all and jokingly fancied notions of leaving the chimpanzees behind to study these lovely gorillas instead. All too soon, however, our time with them ended. Visits with the gorillas are limited to one hour, which may help lessen both gorilla stress and disease transmission risk.

Silverback male mountain gorilla. Photo: Jack Lester.

Silverback male mountain gorilla. Photo: Jack Lester.








Young mountain gorillas feed on dead wood. Photo: Jack Lester.

Young mountain gorillas feed on dead wood. Photo: Jack Lester.








On our hike back to camp, I couldn’t help but laugh about the setting in which we found the gorillas. We were prepared for a serious hike through the so-called “Impenetrable Forest.” Instead of deep forest, however, our visit with the gorillas was situated in steep hillside outside the national park in gardens and uncultivated lands. We were disappointed about not seeing more of the forest. Given our usual work studying chimpanzees in degraded and cultivated habitat, however, it seemed all too appropriate that we should find the gorillas in such a place. In the end, it did nothing to lessen what was a gorgeous and awe-inspiring day. Long live the mountain gorillas!

This post was originally published at Scientific American

Meet the Gents

Though my study covers a broad geographic area, encompassing the home ranges of numerous chimpanzee communities, we have focused substantial attention on one community in particular. This community serves as a focal point for ecological data collection and, when possible, behavioral observations. After months of tracking these chimpanzees in an effort to collect fecal samples, we’ve had the opportunity to repeatedly observe some of the individuals in this community. In such instances, it has been helpful to give them names rather than to refer to them as “the one with the scar on his back,” “the one with the freckled face,” etc. With that in mind, I introduce you to a few of the males we’ve met.


His name means “old man,” which seems fitting given his elderly appearance and behavior. He’s a bit rough around the edges in the looks department…yellowed teeth, scraggly hair, and a weathered face. He also has what we refer to as shoulder pads, meaning the hair on his shoulders sticks up in a disheveled-looking way. In addition, he is easily distinguished from the other males by his pale, freckly face.

Mzee. Photo: Jack Lester.

Mzee. Photo: Jack Lester.










Nonetheless, he has his charms and seems popular among the other chimpanzees in his community. Just check out the trust he has in fellow male Caesar as he grooms a…shall we say…sensitive area. (See photo below.) Males groom to cement social bonds, and such a delicate task surely requires great trust among friends or kin. Indeed, male relationships are very important among chimpanzees. Because they remain in their birth community through adulthood, males have long-lasting relationships with other males who are sometimes kin members. They often form coalitions with other males, which may thereby serve to aid a male’s status in the social hierarchy.

Caesar grooms Mzee. Photo: Maureen McCarthy.

Caesar grooms Mzee. Photo: Maureen McCarthy.









In stark contrast to Mzee’s eccentric appearance, Caesar is a very handsome chimpanzee with an extraordinarily hairy face. This characteristic always reminds us of the character from Planet of the Apes, hence the name.  He was one of the first chimpanzees we saw from this community, and his appearance left a strong impression. He appears to be of prime age, and we suspect he is very high-ranking. Only with more observations can we begin to tease apart the complexities of the social hierarchy with any certainty, however.

Caesar. Photo: Maureen McCarthy.

Caesar. Photo: Maureen McCarthy.









So named for his distinctive and bushy “porkchop” sideburns. The hair on his shoulders sticks up just like Mzee’s, leading me to wonder whether Mzee in his younger days bore a strong resemblance to the present-day Porkchop. Perhaps they are closely related.

Porkchop. Photo: Jack Lester.

Porkchop. Photo: Jack Lester.











Caesar’s ally, and a charismatic male in his own right. He seems to be a nice fellow, though his typical relaxed facial expression portrays more of a frown than a kind smile. He also appears to be a prime male in his peak healthy years.

Tyson. Photo: Jack Lester.

Tyson. Photo: Jack Lester.










Clayton is a young adult male who seems to be attempting to work his way up the hierarchy. We have observed him at times interacting with the other males, while at times keeping his distance from the confident swagger of the older fellows.

Clayton. Photo: Maureen McCarthy.

Clayton. Photo: Maureen McCarthy.









This young male remains somewhat of a mystery to us. We have only a couple of good observations of him. From this, we’ve gathered that he is roughly in his late teens. On several occasions when the other adult males were present, Newton has been absent (or at least not visible to us). We hope to get to know him better in the coming days.

Newton. Photo: Jack Lester.

Newton. Photo: Jack Lester.








We are only just getting to know these males, so there is still much to learn. How are male relationships affected by this degraded habitat? For example, in larger forests where chimpanzee communities neighbor each other, males often patrol their boundaries to look for outsider males. Do these males engage in patrols, and if so, how? Unanswerable questions also come to mind. For example, what must an old male like Mzee think of all of the changes in his habitat since he was a youngster?  We can only speculate and enjoy the opportunities we get for a sneak peek into the life of a male chimpanzee here.

Porkchop, Tyson, and Clayton pant hoot. Photo: Maureen McCarthy.

Porkchop, Tyson, and Clayton pant hoot. Photo: Maureen McCarthy.









This post was originally published at Scientific American.

Conservation Conversation

Greetings are very important in Ugandan culture. Where we work, it is customary to greet those you encounter with a standard exchange in Runyoro, the local language here. For example, if we find a farmer working in his garden in the morning, we might initiate the following conversation:

“Thank you for your work.”
“Thank you for your work also. You are welcome here.”
“How was the night?”
“The night was fine.”
“What is the news?”
“No news.” (Note: It is important to respond in this way even if you do have very big news. You will go on to share that news later in the conversation, but for now, this is the standard reply.)
“How is this place?”
“This place is fine.”

This typically marks the end of pleasantries as well as the end of Jack’s and my conversational repertoire in Runyoro. From there, field assistant Nick continues the conversation by chatting with people and finding out whether they’ve seen or heard chimpanzees recently.

So began an unusual conversation a few days ago. In our unending quest to find evidence of chimpanzees, we turned onto a dirt trail that runs parallel to a surprisingly intact strip of riparian forest. A farm borders the forest strip, and our path led us to the home of the farmers who own that land. There we found an old man, a young man in his late teens, and several small children. Nick made some initial inquiries in Runyoro, and the young man, named John Mary, began to speak in an animated way. He switched to English and explained that this patch of forest belongs to his family. Nick implored him not to cut their trees. He replied that, ah no, they were cutting trees here some years back, but a couple of NGOs came to educate their family about the importance of protecting natural forests. They stopped cutting and hope to plant more natural trees there in the near future. He said that it is difficult to convince others to do the same. We shifted our gazes across the river, where people were busy cutting down trees for timber and to make way for crop fields. He said that the older landowners around here rent out their land for farming, and that as long as they receive their rent money they don’t mind what people do with the land. He expressed frustration that they don’t think about the impact of forest cutting on their children and grandchildren. They only want to get the money to fill their bellies now, because soon they will die and then they cannot eat, he said with a laugh.

Photo 1

Riparian forest is cut for timber and agriculture. Image: Maureen McCarthy.









The topic shifted to where he heard the chimps vocalizing that morning. We thanked the family and said our goodbyes, continuing along the path in the direction where he heard them. His words echoed in my mind as we went on our way. He is a great example of the power of education programs. His family stopped logging and is committed to the notion of forest conservation. All this talk of forests wasn’t mere rhetoric for our benefit. The evidence is easy to see—it’s leafy, green and, still standing tall in remarkable abundance.

A satellite image shows a network of riparian forest fragments in the study region. Image: Google Earth.

A satellite image shows a network of riparian forest fragments in the study region. Image: Google Earth.








John Mary will leave his farm soon to resume his schooling in town. In the coming years, he will continue to fight an uphill battle to protect his family’s bit of forest. From impoverished local individuals to large multinational corporations, many have a stake in what happens to community-owned forests like these. Because of conservation organizations and people like John Mary, however, the value of natural forests to the livelihood of chimpanzees, humans, and entire ecosystems cannot be ignored.

This post was originally published at Scientific American.

Rising Conflict

It was a day off from the field, an opportunity for a bit of mental respite and physical relaxation. The quiet peace of the day was halted, however, when I received an alarming text message from my field assistant, Nick. In it, he relayed the news he’d just heard on the local radio station: a chimpanzee attacked a six-month old infant in a nearby village. The infant had been taken for medical care in town. The parents sought compensation from the government and a local NGO.

I thought back to our visit to this village just days earlier. While there, we met with the village chairman, who said that chimpanzees harassed people there but no one had been attacked to date. Though many trees have been cut for timber and to plant gardens, he assured us that community members were interested in reversing this trend through tree planting efforts. More trees would translate into more habitat for chimpanzees and, hopefully, fewer instances of conflict with them. The chairman and his wife already had some knowledge of chimpanzees, their relationship with the forest, and the need to protect them.

Now, just days later, I wondered…How severely was the child injured? What were the circumstances leading to this unfortunate event? How would an attack on an innocent child affect human attitudes toward chimps?

A few answers emerged when we visited the infant’s family. They said that the children were sitting in the garden, and that one child–aged 4 or 5 years–was holding the infant. No adults were around. (This is a common scenario, since children here often care for one another while adults work in the garden or engage in other chores.) A party of chimpanzees passed by the house on their way toward the forest. What happened next remains uncertain. When chimpanzees come near peoples’ homes, they are often threatened and chased. Whether the children did anything like this is unclear. What we do know is that one of the chimpanzees took the infant from the arms of the child holding her. The older child yelled for help and others, including several adults, came running. They chased the chimp, who proceeded to drop the infant in a cassava garden and run to the forest. Though the infant was injured, the injuries were not life threatening and the child is now making a full recovery at home.

The father explained that he wants to help chimpanzees, that he understands that they are losing their forest and that they are forced to come into gardens. He had no wish to retaliate toward the chimpanzees as a result of the incident. He also feels that people should receive at least some small measure of support if they are to protect chimps, however. Chimpanzees are a protected species, but what recourse do people have if chimpanzees take their food or behave aggressively? What protections are in place to compensate or aid people who suffer crop losses or personal injury? One family member suggested that there could at least be some funding in place for medical care in the event of an attack such as this. Hospital costs due to chimpanzee injuries, though rare, are prohibitively expensive for families such as theirs. We left their home feeling sympathetic for all involved, humans and chimpanzees alike. We could offer no easy solutions.

The truth is that there are no easy solutions. Educational programs can help teach people why chimpanzees behave aggressively and how to avoid conflict.  For example, there is a common belief among villages we visit that chimpanzees are becoming increasingly aggressive. On numerous occasions, people have suggested that we might be replacing their old friendly chimpanzees with mean chimpanzees. Children peer inside our vehicle when we arrive to see if there are angry chimpanzees inside, waiting to be led to their new home. In reality, the behavior of these same chimpanzees is altering accordingly with habitat loss and increasing human pressures, including frequent interactions with humans.

Humans and chimpanzees sometimes must compete for resources in close proximity. Photo: Maureen McCarthy.









Indeed, this sadly is not the first time such an incident has occurred in this region. Deforestation has led to chimpanzee habitat loss and fragmentation, with humans logging more of the forest on a daily basis. Forest trees are logged for timber and clear-cut to make way for agriculture, often for cash crops like sugar cane, rice, and tobacco. Human population growth accelerates environmental changes. Uganda is consistently ranked as having one of the highest population growth rates of any country on earth. With less forest and more cultivated crops, chimpanzees must forage in gardens and come into frequent contact with people.

In The Chimpanzees of the Budongo Forest, Vernon Reynolds (2005) described other instances of chimpanzee aggression toward humans in this region. For example, he reported that “a girl was attacked by a chimpanzee in the forest while she was with her mother and other women and children collecting firewood in the forest. The girl was bitten on the upper leg, genitals and hands, and hospitalized for two months. In revenge for this attack, the villagers of Kirima hunted and killed a juvenile chimpanzee in March 2002” (p. 218).

This example illustrates the bi-directional nature of the conflict. Humans become fearful, annoyed, and at times angry with chimpanzees who eat their crops and threaten their families. Chimpanzees, on the other hand, must forage somewhere for food in their rapidly changing landscape. When their perceived encroachment onto peoples’ land leads them to be chased, threatened, and aggressed upon by people, it comes as no surprise that chimpanzees sometimes behave aggressively as well.

Reynolds (2005) further described the chimpanzees’ situation in this way: “While their image in the eyes of local people is thus deteriorating, we should not blame them. Their actions are the direct result of human interventions in their habitat. The bad character now attributed to them in this area is wholly understandable; human beings equally threatened would react in similar ways” (p. 216).

From a biological perspective, this situation can simply be viewed as a competition for resources. It is to be expected when members of two species must compete for access to limited resources. From the human perspective, however, it’s a complex and heartbreaking situation. It is also a situation that reminds us of a shared trait that binds us with chimpanzees, one that we prefer not to focus on when highlighting our similarities with them. When families and livelihoods are threatened, members of both species can behave with seemingly ruthless aggression. Only by digging to the roots of the conflict can we begin to find solutions that will aid both chimpanzees and humans.

This post was originally published at Scientific American

Surprise Encounter

Fresh nests and fecal samples. We knew the chimpanzees had nested nearby. Not having seen any signs of their continued presence, however, we assumed they had already left their nests and traveled elsewhere to forage. While examining the nests, we were startled out of concentration by a chorus of pant hoots just nearby. We looked in the direction of the calls. A few chimpanzees were in a fig tree not far away, eyeing us calmly as they stuffed figs into their mouths. We watched them for a few minutes until they climbed down from the fig and traveled along the ground through a nearby bit of forest. After we were certain they were gone, we continued checking for samples, including looking around the fig they left behind.

A chimpanzee watches us from a nearby fig. Photo: Maureen McCarthy.









This is not the first time we’ve been surprised by the chimps. Sure, they can be boisterous and loud. There are times when they’re downright impossible to miss. On other occasions, however, they are so quiet that we can pass right by them and almost fail to notice them. I often wonder how many times we actually have failed to notice them.

So went December. It was a busy month that brought lots of data, including a few surprise encounters with the chimpanzees. Surprises, though inevitable, are not the norm for us. Our direct chimpanzee observations often involve getting reports from farmers who tell us that the chimpanzees are in a nearby tree or patch of forest. When we find chimpanzees, we make every possible attempt to give them their space. We keep a distance of over 50 meters and view them through binoculars. We do not enter an area of forest when we know that they are just inside within 50 meters. Instead, we wait until we are reasonably certain that they have departed before entering to look for samples. This is very important since these chimpanzees are not habituated, meaning they are not accustomed to being followed by people for research or tourism purposes. (See another recent Scientific American blog for additional discussion of habituation and its role in our understanding of chimpanzees.) Habituated chimpanzees can be followed at close range and are—hopefully—undisturbed by human presence. Habituation is necessary to undertake long-term research that provides meaningful insights into the behavior patterns of chimpanzees.

Studying unhabituated chimpanzees means that I can’t rely on close behavioral observations for data collection. The chimpanzees I study typically flee if people come near. This is why I focus on indirect evidence like fecal samples to provide critical data. Even with only some behavioral observations, however, the chimpanzees provide a wealth of information for study. Their nests provide insights into where they choose to sleep, their feeding remains show us what they’ve been eating, their knuckle prints tell us which direction they’ve traveled, and their dung provides…well, all sorts of interesting information.

Studying unhabituated chimpanzees also means that I must take care to avoid causing undue stress to my study subjects. Because these chimpanzees live in small forest patches, they have limited space to flee if we come too close for their comfort. It is for this reason that we keep our distance and enter onto their turf only after they’ve left it.

Photo: Maureen McCarthy.








Given the importance of habituation for actually being able to watch the animals under study, one may wonder why I have chosen not to habituate these chimpanzees. There are several reasons. First, chimpanzee habituation is typically a long and arduous process. It can take one to two years or more, if feasible at all. As a lowly PhD student, I simply do not have the time or resources to undertake such a costly endeavor. More importantly, however, the risks of habituation for these chimpanzees may outweigh the benefits. Because they are often in conflict with the humans around them, being wary of people may actually work in their favor. The more comfortable they become with people, the more they may be at risk of aggressive encounters with their human neighbors. My colleague Matt McLennan (as mentioned in previous posts) has cautioned against habituating chimpanzees in our study region for ecotourism, saying that “habituation for tourism is inappropriate where apes and people live in very close proximity, for reasons that include increased likelihood of crop-raiding, risk of aggression toward local people and tourists by emboldened and/or stressed chimpanzees, and increased potential for disease transmission. Instead, habitat stabilization and enrichment must be the priority” (McLennan 2008, p. 52).

This study region is not unique in posing ethical concerns regarding the primates inhabiting it. Primatologists around the world must consider the ethical implications of various research methods, and design their studies accordingly. Just as lab scientists must consider potential risks to their study subjects in an effort to minimize harm, so must field scientists consider the potentially negative impacts of their research. Collecting data is only one aspect of the job. Personal, ethical, and emotional rewards and challenges are a part of everyday life. For me, this is what makes research an exciting, layered, and often imperfect experience.

This post was originally published at Scientific American

Travels In and Out of the Forest

Humans are very poorly adapted to a chimpanzee lifestyle. I am reminded of this on a nearly daily basis as we trace the locations where chimpanzees have been hanging out. I regularly trip over vines and tree roots, slip off logs, and slide down muddy hillsides. I have tumbled to the ground no less than eight times in the past week. In between bouts of tripping, stumbling, and cursing, I find myself marveling at the strength and agility required to live in this forest habitat.

Chimpanzees are remarkably agile and well adapted to live in a variety of habitats in equatorial Africa. They are gifted climbers, and they also travel swiftly and gracefully on the ground as quadrupeds. In addition, they have staggering strength. A classic series of studies by John Bauman in the 1920’s demonstrated that chimpanzees have more than four times the strength of a human. While it is a difficult feat to measure this accurately, there is no doubt that chimpanzees are very strong indeed. Anthropologist Alan Walker described their strength as follows:

“On one occasion, I was minding my own business while walking along a forest trail when I nearly bumped into an adult male chimpanzee that was doing the same. The frightened animal swung at a nearby tree buttress root, making a resonating booming sound. After this display, the animal raced up the trunk and proceeded to shake branches high above me. When my heart rate returned to normal, I tried to imitate the chimpanzee by banging on the buttress as hard as I could. I could produce only a laughably feeble sound. Thus it was that I came to appreciate firsthand what many people know anecdotally—that great apes are immensely strong.”

(Note: If you happen to encounter an adult male chimpanzee in the forest, I would not advocate Walker’s response as your first recourse! Still, you get the idea.)

As I’ve struggled to maintain my clumsy upright posture, I’ve snapped a few photos of chimpanzees being their graceful selves in the trees.

A juvenile chimpanzee hangs out while foraging. Photo: Maureen McCarthy.










A juvenile chimpanzee swings between branches. Photo: Maureen McCarthy.


An adult male chimpanzee moves along a branch. Photo: Maureen McCarthy


















Outside the forest, traveling hasn’t been much easier lately. In the past couple of weeks, we’ve had multiple vehicle problems. First, our beloved vehicle, Lucy, broke down just after a visit with friends in the next district over. It was the sort of malfunction that involved broken bits of metal falling onto the road and oil leaking out, leaving a disastrous Hansel-and-Gretel trail of vehicle mayhem behind. We had to call a tow truck to pull Lucy from a small dirt road to the nearest town. It’s not uncommon for trucks here to have short, snappy sayings painted onto the front of them. Our tow truck bore the slogan “Dangerous Toweling”. Somehow, this didn’t inspire my confidence. Nonetheless, we made it back to town without incident.


Lucy gets a tow into town. Photo: Maureen McCarthy.










It looked like we might be without a research vehicle for a week or two. Luckily, we were able to have our mechanic in Kampala send spare parts via bus the very next day. Jack put his mechanical skills to work and replaced the broken parts in no time. Thankfully, what looked like a serious setback was remedied in less than 24 hours.

Next, just days later, we got two flat tires. Unfortunately, both tires went flat on same day. The back right tire went flat, so we tested the spare in preparation to make a swap. The spare was also flat. Our portable compressor saved the day until we arrived back in town to get both tires repaired. These two tires are among the eight or so flats we’ve had in the past couple months. The good news is that I’ve never been so good at repairing flats. I have to admit that it might be time to invest in some new tires, though. Until then, we’ll keep chugging along, over forest tree roots and dirt road potholes alike.

Jack and field assistant Nick repair a flat tire. Photo: Maureen McCarthy.









This post was originally published at Scientific American

Lessons from Washoe

October 30th marked the five-year anniversary of the death of my friend Washoe. Washoe was a wonderful friend. She was confident and self-assured. She was a matriarch, a mother figure not only to her adopted son but to others as well. She was kind and caring, but she didn’t suffer fools. Washoe also happened to be known around the world as the first nonhuman to acquire aspects of a human language, American Sign Language. You see, my friend Washoe was a chimpanzee.

Washoe was born somewhere in West Africa around September 1965. Much like the chimpanzees I study here in Uganda, Washoe’s mother cared for her during infancy, nursing her, carrying her, and sharing her sleeping nests with her. That changed when her mother was killed so baby Washoe could be taken from her forest home, then bought by the US Air Force for use in biomedical testing.

Washoe was not used in this sort of testing, however. Instead, Drs. Allen and Beatrix Gardner of the University of Nevada chose her among the young chimpanzees at Holloman Aeromedical Laboratory to be cross-fostered. Cross-fostering occurs when a youngster of one species is reared by adults of a different species. In this case, humans raised Washoe exactly as if she were a deaf human child. She learned to brush her teeth, drink from cups, and dress herself, in the same way a human child learns these behaviors. She was also exposed to humans using sign language around her. In fact, humans used only American Sign Language (ASL) to communicate in Washoe’s presence, avoiding spoken English so as to replicate as accurately as possible the learning environment of a young human exposed to sign language. Washoe began to acquire ASL signs at a young age, and her sign acquisition increased with a pattern bearing many similarities to a young human child’s language acquisition. She used these signs to communicate with humans and, later, with other chimpanzees who also acquired these signs*.

Washoe. Photo: Courtesy Friends of Washoe, used with permission.











Washoe’s use of ASL signs was groundbreaking. It altered our understanding of what it means to be human. Language was thought to have set us apart from other animals, making us unique among all species. Washoe and her chimpanzee family forced revisions of these old anthropocentric assertions. Later studies showed that all great apes—chimpanzees, bonobos, orangutans, and gorillas—can acquire aspects of human language.

As impressive as Washoe’s role in our understanding of human-ness was, it was not what impressed me most about her. After all, by the time I met Washoe a decade ago, her contributions to debates regarding human uniqueness were well established. Instead, as an intern and later as a master’s degree student at Central Washington University, I was most impressed by the kind of being she was. Here are just a few examples.

She had a strong sense of self. Washoe came to know many human friends at the Chimpanzee and Human Communication Institute (CHCI), her home for over 25 years. Students and interns come from all over the world to study and care for Washoe’s family. As such, Washoe was slow to warm up to strangers. Though she would often ask to see a new person’s shoes (she had an affinity for footwear and would always notice if caregivers had a new pair of shoes), it sometimes took months or more before she trusted people enough to share more in-depth interactions. The training process for chimpanzee caregivers takes several months as the chimpanzees come to know you and you learn how to safely interact through the fencing that separates them from you. For the safety of both, caregivers never penetrate the fencing or enter into the chimpanzees’ enclosures while they are inside. As a trainer for new caregivers, I witnessed Washoe’s relationships develop with numerous friends. In general, she and the other chimpanzees can read people like nobody’s business. She could size up a new person in an instant. Perhaps most importantly, she sensed whether or not you knew she was boss. She was the alpha (most dominant) chimpanzee in her chimpanzee and human family, and she expected to be treated that way. Washoe could easily spot a new person who appeared arrogant or who “talked down” to her. It wasn’t a good way to earn her friendship easily, and subsequently, newbies usually learned quickly about the rules of chimpanzee society. It was always best to greet Washoe first, to serve her dinner first, and to leave a little extra so she could be sure to have a bit more if she wanted it. These acts were not indications of favoritism. They were simply ways of taking the chimpanzees on their terms, of recognizing that Washoe was alpha and that alpha status in chimpanzee society affords certain advantages. The other members of her chimpanzee family also understood and expected this.

She drove a hard bargain. Once, after some maintenance men completed repairs, I discovered that they had inadvertently left a wrench very high on a ledge of one of the chimpanzees’ enclosures. Unfortunately, I found this out when I greeted Washoe and saw that she was busily testing the bolts along the enclosure’s fencing with the wrench. Luckily, she really wasn’t getting far with it, but I certainly didn’t want to explore the limits of her mechanical skills. I needed to get the wrench back, but how? I decided to try for a trade. Though the chimpanzees have a far healthier diet than me most of the time, they enjoy treats every once in a great while. Coffee is a favored treat beverage, so I poured some coffee with creamer and excitedly presented it to Washoe and Tatu, who also happened to be nearby. I signed to ask for the wrench back. Tatu seemed eager to take me up on the offer, but Washoe looked unimpressed as she continued to clutch the wrench. It was time to up the ante. Washoe loved soda, so I poured some of that instead. This piqued her interest, so I asked for the wrench again. She gladly handed it over and enjoyed the soda along with Tatu. Washoe knew that the first rule of negotiating is never to accept a first offer. It paid off.

She was brainy and creative. When caregivers at CHCI clean the chimpanzees’ enclosures, they use hot water from hoses to spray down and rinse areas. While caregivers clean an area the chimpanzees are no longer using, the chimpanzees sometimes come to the fence of an adjacent room and ask for drinks from the hose. Washoe often liked to sip her hot water from a cup as she watched us clean. Sometimes she also made herself a day nest and reclined luxuriously as warm steam poured into her enclosure through the fence, creating her own personal sauna area. On this particular day, she looked around, but no cups were nearby. Instead, she picked up the hollow rubber head of a baby doll. (Though Washoe liked children, baby dolls didn’t often fare well in her care.) She inverted the doll head and held it up to the fence so I could aim the stream of hot hose water into the head. Though I probably never would have considered the functionality of this object as a container, Washoe quickly solved the problem and found herself a perfectly good cup.

Though Washoe was a very unique individual, she was in other respects an ordinary chimpanzee. That is, she was not a brilliant exception among chimpanzees. The other members of her chimpanzee family also acquired ASL signs. Though her upbringing was distinct, she shares a great deal with the chimpanzees I study here in Uganda. Chimpanzees here share similar sentience, a similar reliance upon gestural communication (while using a somewhat different set of gestures), and a similar capacity for joy and pain. Thus, while Washoe is a great ambassador for chimpanzees, she should not be placed on a pedestal as uniquely gifted among her kind. She is just one chimpanzee of many taken from her African forest home and transferred to an utterly foreign place to lead an altogether different life than the one she would have otherwise had. Thankfully, it’s no longer legal to capture chimpanzees from Africa and transport them abroad. It still happens occasionally, but realistically, threats like bushmeat hunting and habitat loss pose much greater risks to free-living chimpanzees today. Though I miss Washoe now and always, I’ll always be grateful for the many lessons she taught me about herself and her kin which, after all, includes us humans too.

*The members of Washoe’s chimpanzee family at the Chimpanzee and Human Communication Institute are equally spectacular beings, with their own fascinating life histories. This “family” is not biologically related, but has been a stable family unit for over 30 years. Read more about the others—Moja, Tatu, Dar, and Loulis—at

Learn more about Washoe and her family:

This post was originally published at Scientific American