Dr. Potts’ final notes from Uganda

three chimpsI’m now sitting in the Entebbe airport, waiting for my flight out of the country, back to the US. For my last post, I thought I would say something about the conservation status of chimpanzees in general, and that of chimpanzees at Ngogo in particular. This is an issue I think about often, as I’ve watched the precipitous decline of chimpanzee populations throughout equatorial Africa over the last decade or so that I’ve been studying this species, while at the same time witnessing the fairly dramatic increase in community size and density of my study community at Ngogo. Like virtually all the great apes, chimpanzees are considered endangered – certain populations, or “subspecies”, are considered critically endangered and will likely disappear within my lifetime. The fate of wild chimpanzees will be dictated in the near future by the effects of several interrelated factors: habitat loss (both legal and illegal), bushmeat hunting/poaching, and episodic disease outbreaks. Logging and mining operations have decimated chimpanzee habitats (the species is unlucky to inhabit areas rich in both precious hardwoods and rare minerals), especially since the discovery of oil in several African countries with large chimpanzee populations. While some of my work in the past has shown that low-intensity selective logging can be compatible with chimpanzee conservation, large-scale clear-cutting for commercial timber or mineral extraction certainly cannot. In many African countries in which timber operations have opened up access to forests inhabited by chimpanzees (and other primates), illegal bushmeat hunting, usually through the use of wire snares in which chimpanzees become entangled, has increased dramatically. There is a misperception among many in the western world, however, that the bushmeat “issue” is one that stems primarily from the need for local villagers in areas occupied by chimpanzees and other primates to obtain a steady source of protein. If this were the case, the problem could, in theory, be easily solved by providing alternative sources of protein to these populations. The truth, it turns out, is that the non-sustainable poaching of chimpanzees for bushmeat is largely driven by large commercial markets operating out of large, metropolitan areas, including some in the “developed world” (even the US). A large supply of bushmeat was recently confiscated, for example, at Charles De Gaulle airport in Paris, and not long before that at London’s Heathrow and New York’s JFK airports. The consumption of bushmeat is associated with cultural status in many African cultures, and wherever the diaspora of sub-Saharan African elite culture spreads, whether it be Nairobi or New York, there is likely to be an underground market for bushmeat in those areas. And, as long as that market exists, populations of chimpanzees and other unfortunately easily-caught primates will continue to decline. Finally, the disease issue. This is one that has only relatively recently emerged, largely because many of the diseases that currently decimate chimpanzee populations, primary among them the Ebola virus, only recently began to afflict chimpanzees (and humans, for that matter, who are as susceptible, if not more so, to Ebola as chimps). For as terrifying and dangerous a disease as Ebola is (with upwards of 95% mortality in some cases, it is among the most virulent of all known diseases afflicting primates), we know surprisingly little about it. For example, we think that its primary host is one of a number of species of fruit bat that live in the same forests as chimpanzees (and, in some cases, gorillas), and that apes become infected by using the feeding tree as a bat carrying the virus, but there is not really all that much evidence to strongly support this. What we do know is: 1) the virus is easily transmitted between humans and chimpanzees, primarily through contact with bodily fluids, and 2) once a chimpanzee in a particular population is infected, it spreads extremely rapidly and, as I just mentioned, has a very high mortality rate. Recent Ebola outbreaks have virtually destroyed otherwise thriving chimpanzee populations, for example the previously very large population in the Tai Forest in Côte d’Ivoire in far Western Africa. Ebola is almost single handedly responsible for giving western lowland gorillas the unenviable “Critically Endangered” designation on the IUCN’s Red List of Threatened and Endangered Species. But it is not just the scary, horrifyingly grim pathogens like Ebola that threaten the long-term viability of chimpanzee populations. Seemingly far less insidious diseases, such as simple upper respiratory tract infections, which may have little to no external manifestations in humans, can wreak havoc on a chimpanzee population in which individuals lack immune responses to such infections. In Gombe National Park, for example, where Jane Goodall’s famous study of chimpanzees was first initiated in the early 1960s and continues today, retrospective analysis of major mortality events in the chimpanzee population there showed that there was a very high probability that the deaths were caused by respiratory illnesses spread from humans to chimps. As researchers, we come into fairly close contact with our study animals, and we need to be cognizant of the fact that they can easily become infected by a simple cold virus that we may be carrying, and that such a virus can be much more dangerous to their health than to ours.


All of these factors are working in consort have led to a major decline in wild chimpanzee numbers over the last decade. However, as I mentioned at the beginning of this post, the chimpanzees at my study site, Ngogo, have not only avoided such decline but have positively thrived over this same period. When I first started studying chimpanzees at Ngogo in 2002, there were about 140 chimps there (already more than twice the size of the next largest community anyone knew of). Today there are almost 200, nearly 4 times the size of the next largest known community. This is astounding, considering what is happening to chimpanzees elsewhere. I look at the chimpanzee community at Ngogo with a sense of guarded optimism, however, for its “success” comes with some caveats. The forest at Ngogo has been relatively unaffected by resource extraction in the past, but massive reserves of oil were recently discovered in western Uganda and there is no reason to believe these reserves are not going to be exploited to their fullest extent, and any forest that must be cleared in the process will be considered collateral damage. Chimpanzees at Ngogo have not been directly targeted for bushmeat, largely because of a taboo that exists in the cultures of the local Batoro and Bakiga tribes that surround Kibale National Park against eating primates, but there is evidence that Congolese refugees fleeing civil war in eastern Democratic Republic of Congo have moved into the area east of the Rwenzori Mountains, just outside Kibale, and have started poaching chimpanzees (no such taboo against eating primates exists in these cultures). The chimpanzees at Ngogo have not been affected by any major disease outbreaks in historical times, but Ebola outbreaks have hit several human populations not far outside of Kibale, and there is no reason to think that the virus cannot spread into the park (particularly if people poach and eat chimpanzees).


Given all that, I don’t want to end this blog on a pessimistic note. Despite all these caveats, Ngogo is still the best place on Earth to see and study chimpanzees. There is no other place in the world where you can hike into the forest and see upwards of a hundred chimpanzees in the same area. It is an experience I can’t adequately describe, except to say that I feel privileged to have the opportunity to witness such a scene. I hope you’ve enjoyed reading this blog as much as I’ve enjoyed writing it. I’m always happy to share photos and stories with anyone who’s interested, so once I’m back on campus feel free to track me down. I’ll be the one with the beard that looks like a chimp’s.

More from Uganda (courtesy of Dr. Kevin Potts)

I have two short posts this time, one that might be somewhat informative and one that is completely inconsequential and should only be read by those with a desperate need to procrastinate.


Let’s start with the dumb post: I’m beginning to look and to smell like a chimp. I always seem to become aware of this around this time in a field season, when I have just a few more days in the forest before having to re-enter civilization. First, looking like a chimp – this is not much of a stretch for me. My beard always has a somewhat simian-esque quality about it, and now it’s been growing for far too long, as has my hair (I never shave or cut my hair when I’m in the field), so I’m truly entering Dr. Zaius/Planet of the Apes territory. Those of you lucky enough to see me within my first few days back in Minneapolis will get to see this spectacle in all its glory. People occasionally stop me on the streets of Kampala or Fort Portal after I’ve been in the forest for a long stretch of time and say, “Hello, Jesus” (one guy several years back seriously thought I WAS Jesus). As for the chimp smell: chimpanzees have a very distinctive musk – you can smell when they’re in the area – and it’s so pervasive that it remains on the vegetation that they come into contact with. So, if you’re following behind a big group of chimps, passing through the same thick vegetation that they’ve just passed through, well, you’re going to get a bit of chimp aroma on you. Because washing machines are rather difficult to come by in the forest, we re-use our field clothes for a good week or so before washing them, which gives the stench plenty of time to settle on our skin. And, man does that odor like to stick around! We do have “showers” here in camp, which consist of a little shack in which you can bring a pail of water to dump on yourself and, well, you get the idea. It really just sort of moves the dirt around rather than actually gets you clean. So, the chimp-ish smell tends to stay around until I can get access to a good, hot shower (one nice perk of having to go back through Kampala before leaving to go back to the US). Even then the smell seems to linger for a while. I always feel bad for the person sitting next to me on the flight from Entebbe to Amsterdam, and Amsterdam to the US. Those poor folks didn’t know that they were going to be getting occasional whiffs of Eau de troglodytes for 9 hours in a stuffy cabin with poor air circulation. That’s what you get for flying economy class!


OK, now on to the post with at least some substance to it. This one goes out to all you plant aficionados out there (I know there are some of you). I figured, since my primary objective this field season, and one of the primary objectives of my research for the next year or so, is to collect samples of plants fed on by chimps, to analyze their chemical properties and characterize their nutritional quality, I ought to say something about some of the plants in the forest here in Kibale. I mentioned in an earlier post that we are currently experiencing something of a bumper crop of Uvariopsis congensis fruit in this part of the forest. Uvariopsis is a small tree, but it grows in extremely dense groves, with a dozen trees within just a few meters of one another, and chimps can easily move from one to another without having to come to the ground to travel. It is among the most abundant of all trees at the Ngogo site – rivaled only by one or two other species that, interestingly, chimps mostly ignore as food sources. During this particular fruiting event, essentially every Uvariopsis tree in the forest is fruiting (at least all of the trees that I’ve seen), and unlike most fruiting seasons, this one is lasting a LONG time. It’s been going strong for about a month and a half now, and is showing no signs of abating. So, this is a somewhat unusual event, something akin to what plant ecologists working in Dipterocarpaceae forests in Borneo or in oak forests in the eastern US would consider a “mast” fruiting event – virtually all individuals in an area producing fruit (and seed) at the same time. There have been some interesting occurrences that, I strongly believe, are linked to this “masting” event. For example, my old friends the bush pigs seem to be everywhere in the forest these days (not exactly the safest time to be wandering through the forest if you’re a researcher). On a few occasions, I’ve returned to camp in the evening having not obtained a particular plant sample I was hoping to get that day, and David (the only other researcher in camp now) would say something to the effect of, “oh, well tomorrow you should try going out to F/6.5, there’s a big Ficus natalensis out there with lots of fallen fruits”. So, first thing the next day I’d head out to F/6.5 to find the F. natalensis, only to find either a) bush pigs scarfing up all of the fruits on the forest floor, or b) absolutely no fruit on the ground put plenty of pig dung. This has happened a few times and, despite being quite frustrating (it’s not pleasant hiking an hour or more to a particular tree without finding anything there), it’s kind of interesting. Plant ecologists working in Indonesian Borneo, where trees of the Dipterocarpaceae family produce seed during “masting” events once every several years, have proposed that this seed production strategy is an evolutionary response to the threat of seed predation. In particular, in that region, during a dipterocarp masting event, bearded pigs (the primary “predators” of dipterocarp seeds) move into the area in droves. However, the dipterocarp community produces such an overwhelming abundance of seeds that fall to the forest floor, that even with this huge influx of bearded pig vacuum cleaners sucking up all the seeds they can possibly eat, there are still plenty of seeds left intact after the pigs become satiated. Could something similar be going on in the case of Uvariopsis at Ngogo? Produce a huge amount of fruit, much of which will fall to the forest floor, which in turn will draw migratory fruit-eaters (like bush pigs) into the area to feed, and “hope” that they become satiated before all seeds have been gobbled up? Of course, many of the seeds will pass through the gut of the pigs completely intact, and therefore be dispersed. One other intriguing piece of evidence here is that, for the first time that I can remember, there is so much Uvariopsis fruit sitting on the forest floor that much of it is decaying and molding (so obviously not being eaten by any vertebrates). I’ve been working in this forest for over 10 years, and there are still interesting events like this that continue to surprise me.


So, there you have it: one post that might have taught you something, and one that was surely a waste of your time. I guess the two even each other out.

The Latest from Uganda

I’m sometimes asked “what’s it like to follow chimpanzees through the forest?”, and the completely unsatisfying answer is that it depends entirely on which chimp, or group of chimps, I’m following. Tracking a big group (and, with close to 200 chimpanzees in the Ngogo community, groups can be REALLY big) full of adult males is a completely different experience than following, say, a mother and her young infant or juvenile. Big groups of adult males do what big groups of adult males of most species will do – they display for females by trying to beat each other up, they run all over the place making lots of noise along the way, they may take a nap or two at some point, then resume beating each other up. Spending the day in the forest with a mother and her young offspring, however, is often nothing like this testosterone-driven frenzy at all.

For example, the other day I went out to collect some fruits from a large fig tree that the chimps like to pig out on (stop me if I’m using too much technical jargon). When I got to the tree, I unfortunately didn’t find too many figs to collect, but I did happen upon a very old adult female chimpanzee named Marlene, plus two of her kids (Hayden, who is a young adolescent male who still hangs around with mom quite a bit, and a juvenile female whose name escapes me). Side note about naming conventions for the chimpanzees at Ngogo: I should have mentioned this in an earlier post. My former PhD advisor, David Watts, who co-directs the Ngogo Chimpanzee Project, is a jazz nut, so from the beginning most of the male chimpanzees (who were “habituated”, or became accustomed to and accepted, the presence of humans earlier than most of the females) in the study community were given names of jazz musicians – Miles, Monk, Coltraine, Ellington, Brubeck, Mingus, Dexter, etc. There are some exceptions, most of which are classical composers’ names (my all-time favorite chimp, Stravinsky, who sadly went up to chimp heaven a few years ago, for example).  The same jazz-themed naming convention was started with the females (e.g., Fitzgerald, Lady Day, Ma Rainey), but David started running short on female jazz musician names. He then turned to another of his interests, opera, and started naming female chimps after opera singers (e.g., Fleming), but this also proved to be a dead end. So, “new” females (in the process of habituating a chimpanzee community, it can take many years to find and habituate all of the members of the community, particularly the females) were given names of famous actresses, and that convention has stuck – Jolie, Sigourney, Meryl, Sarandon, Bacall, Kidman, Halle (Berry), etc.

Which brings me back to Marlene, named for the actress Marlene Dietrich. She’s been around for a long time and is one of the most “successful” mothers in the Ngogo community (with “success” defined in terms of surviving offspring). Unlike the boisterous displays and calls that accompany a large group of adult males, and perhaps also an unfortunate estrus female who happens to be the object of the males’ affections that day, mothers and their dependent offspring often travel in very small parties (or alone in their little family group) and barely make a peep. Such was the case with Marlene and her kids. When I first heard them rustling through a grove of Uvariopsis trees (mmmm…. sugar),  I just assumed, without looking up into the canopy, that it must be a small group of monkeys, maybe mangabeys or redtails, because they were treading so quietly and softly through the trees. But then I glanced up into the tree to see a little juvenile female chimp staring me down. She stared at me for a good 20 minutes – I stared at her for about 5 before I got tired of the staring contest. Then I heard a crashing sound coming from the Uvariopsis tree next to the one the little juvenile was in, and suddenly, out popped the not-so-photogenic mug of Marlene. They’d been there the whole time, quietly going about their business of getting hopped up on Uvariopsis sugar that I’d almost walked right past them.

It’s often suggested that the reason females, and in particular those with dependent offspring, travel in relatively small groups has to do with feeding competition: the larger the group, the more mouths there are to feed, and females who must devote energy to nourish a growing fetus or to nurse a young infant simply can’t afford to spend time in large parties, in which their share of the food in a given feeding patch will be relatively lower than if they were to forage in smaller parties or alone. Whatever the reason, mothers and their kids will often avoid the big groups, where most of the “action” is, and will also generally remain quiet, perhaps to keep their feeding patch from being seized upon by others who may be in the area. All this makes for a very different chimpanzee-viewing experience. In previous posts I’ve discussed following big groups of males as they charged around, displayed loudly, ran through thick vegetation, caught and killed red colobus monkeys, etc. By contrast, this day spent with Marlene and her little ones was relatively peaceful, almost calming. Females with young kids often don’t like coming down to the ground when a researcher is around, so Marlene was content to spend most of the day traveling through the continuous canopy of the Uvariopsis grove, with her little juvenile in tow. The two played for a while, Marlene tickling the juvenile and vice versa (and this really is tickling as we know it, and is truly “play”, as we know it… if you’ve ever seen it you know it can’t be described in any other way). At one point, Marlene even played a game in which she spit some big Uvariopsis seeds at her little juvenile. The kid tried spitting back, but she obviously didn’t have the chops for it quite yet. They continued on like this for hours, eating, playing, and resting in makeshift “day nests” (chimps make nests out of branches in which they sleep each night, but occasionally will make a nest in the middle of the day if they really need a serious snooze). The little kid continued to try goading me into a staring contest. Hayden, Marlene’s adolescent male, had no problems with me and eventually came down to the ground, but to my surprise he didn’t move off to join the big boys. Instead, he stayed with his mom and sister, content to nap on the ground while they fed and played up in the trees. It was nice to spend the day with this happy little family, an old mother, her young daughter, and older son (who’s still obviously a momma’s boy). Not exactly the same experience as tearing through thick vegetation at full speed while big adult males yell and scream and beat each other up, while in search for monkey meat. So, what’s it like following chimpanzees through the forest? Well, it depends….