Mystery of the Koolakamba

How many types of great ape are there? Primatologists believe that between us, our closest cousins the chimpanzees, the gorillas, and orangutans that there are four genera. Are there any more? Is interbreeding between these non-human genera possible, and if so, what does this mean for humans?

The world is a big place. I mean, a really big place. When I was pursuing a project studying the carnivorous fossas of Madagascar, I remember being told by another primatologist about an even larger predator he claimed to have encountered in Northern Madagascar than the fossa. Although skeptical that such a predator could exist and never be seen on camera, I asked around my colleagues who work in Madagascar. To my surprise, several people corroborated this professor’s story. At least two of them even independently claimed they had seen a picture of the creature: a slick, black, cat-like carnivore on the wall of a cafe in Antananarivo. How could such a thing exist on an seemingly disappearing island with researchers walking around all over it?

I’ve often thought about the weird areas of the world too remote for even the most dedicated field biologists to visit. Areas of Southeastern Cameroon, Gabon, the Republic of the Congo, and the DRC are certainly too remote for most. Uncontacted tribes still exist in the 21st century in both Papua New Guinea and Brazilian Amazonia. What else is out there that we don’t know of?

Mystery Ape at the Yaounde Zoo
Yaounde Zoo Ape
The Yaounde Zoo Ape

In 1996 a photograph was taken at the Yaounde Zoo in Central Cameroon of a dark-colored ape which shocked both primatologists and travelers alike. With piercing orange eyes, dark skin, and a square-chiseled jaw the ape appears to be unlike any other seen before. Described as a possible chimpanzee-gorilla hybrid, the ape is a taxonomic mystery to this day.

To taxonomists at the time who were familiar with the history of the classification of chimpanzees, the identity of this animal was nearly ascertainable: this was WC Osman Hill’s Pan troglodytes koolookamba. Originally classified in the 1800s by French zoologists, this ape was described by Paul Du Chaillu (an American from Louisiana and one of the first European scientists to travel to West and Central Africa) as possessing, in comparison to chimpanzees, “[a] less prominent ‘muzzle’, large supraorbital ridge, high zygomatic ridges…and a larger cranial capacity.” Du Chaillu also noted that compared to chimpanzees, these apes had much larger ears. Based on this historical description from the 1860s, one could conclude that the mystery ape at the Yaounde Zoo was likely a koolakamba.1

According to historical descriptions, the koolakamba differed from chimpanzees in its tendency to use a bipedal gait, its solitary social structure, and in its vocalizations (the ‘kooloo’ refers to the sound, or ‘kamba’, made by the apes).

Where else have these things been seen? According to a post on the Primate Information Network’s website from some time in the 1990s, koolakambas were held in captivity in the United States.2 The taxonomic work on chimpanzees by anatomist WC Osman Hill in which he identified the koolakamba had been conducted at a research laboratory in Alamogordo, New Mexico. Although his description of the koolakamba vastly differed from that of Du Chaillu’s (he argued that the face of the koolakamba was extremely prognathic rather than flat and with small ears rather than large ones), he asserted that his ape and Du Chaillu’s consisted of a subspecies of chimpanzee.3 Dr. Elaine Struthers who worked at the Coulston Foundation labs in Alamogordo, New Mexico, claims that their lab even had at least two koolakambas in its possession before they closed in 2001. She even claims to have a picture taken by Hill from the 1960s of a male koolakamba herself.

Taxonomic Affinity

Two questions surround the mystery ape from the Yaounde Zoo:

  1. Is this ape and the apes of WC Osman Hill the same (are they both koolakambas)?
  2. What exactly is the koolakamba, anyway?

Although Hill described the chimpanzees in New Mexico as koolakambas, they may have been something else entirely. In the mid-1990s, wildlife photographer Karl Amman began looking for an alleged mystery ape located in a relatively unexplored area in the Northern Congo. Purported to be immune to poisonous darts and to hunt lions, these apes were much larger than chimpanzees and nested on the ground, much like gorillas.4 Much excitement was built up around locating this ape and in assessing its affinities as some had suggested it may be a hybrid gorilla-chimpanzee, but in 2004 mtDNA revealed that apes were most likely a sub-culture of the Eastern chimpanzee (Pan troglodytes schweinfurthii).5

One of the few images of a Bili ape. Note the shape of the ears and facial prognathism.

Curiously, although these chimps express a range of behaviors different from other chimps in the subspecies and possesses several of the facial features (including a supposed lack of prognathism) of the Yaounde Ape, there are some problems with identifying this species as the alleged koolakamba. First, Du Chaillu’s purported ape was in West Africa, not in the Northern Congo where the Bili Apes are located. Second, their social organization seems to be typical in that they are still living in normal groups like other chimpanzee subspecies rather than solitary. Third, although described as possessing a flat face and being mid-range in size between chimpanzees and gorillas like the koolakamba, pictures of the chimpanzees show that these apes possess what appears to be exaggerated facial prognathism with small ears set rather close to their head. Compared both to descriptions of the koolakambas and the picture of the Yaounde Ape, these cannot be the same. It’s more than possible that these Bili chimps from Northern-Central Africa were the ones described by WC Osman Hill in the 1960’s, and the apes from the lab in New Mexico tested as belonging to another subspecies of chimpanzee, just as the Bili apes did.

Which leads us to the Yaounde Ape: what is it?

The Case for a Great Ape Hybrid

There are two ways we can look at this ape. We can either assume that it, like the Bili apes of Northern Central Africa, is part of some yet undescribed sub-species of chimpanzee which has yet to be seen by primatologists. This would greatly expand our knowledge of chimpanzee variability, just as the Bili apes are doing today. Or we can believe that this creature is a classical koolakamba: a rare hybrid between gorillas and chimpanzees. I have several thoughts about a hybrd:

My first is that this ape matches Du Chaillu’s anatomical description almost perfectly. From its ears to its flat face, this thing does not look like any other sub-species of chimpanzee. The fact that we haven’t seen anymore of these since also leads me to assume it’s rare, just as a hybrid ape would have to be (although these areas are rather unexplored by primatologists, in fact the primatologists working out there on gorillas are dropped off by helicopters in ginormous treeless patches in the middle of the forest called bais).

The extant range of gorilla species. The location of Gorilla gorilla g. is where both Yaounde is located and where Du Chaillu visited 150 years ago.

Another thing is that if hybridization were going to happen anywhere, it would be here. This area contains both the largest and least scientifically studied gorilla subspecies in the world, and is possibly the only area where the the populations of gorillas and chimpanzees overlap in large enough numbers to make hybridization even a possible occurrence.

Finally, Du Chaillu described koolakambas as being solitary and living on the fringes of the other great ape groups, which would make sense if the animal is a hybrid – dietary, morphological, or behavioral differences could lead to difficulties in finding new groups during dispersal (female gorillas and chimpanzees leave their natal groups during early adulthood and attempt to integrate into other groups). A German naturalist baron named Hugo von Koppenfels claimed in 1881 that koolakambas were the result of rare matings between female chimpanzees and male gorillas – if this is the case, a male koolakamba would likewise have difficulties in acting as a male gorilla in recruiting female gorillas.6 He would hypothetically roam as either a lone male or in a bachelor group, but he might do okay if born as a male into a chimpanzee group social group. Given birth conditions – either born into a gorilla group as a male or a female or a chimpanzee group as a male or a female, there’s a 75% likelihood that a hybrid would likely be solitary.


There are numerous discussions of whether a chimpanzee-human hybrid would be possible.7,8 Although we might think that this is a non-scientific thing to speculate about right now since presumably we won’t be trying this anytime soon and molecular science isn’t far enough to just give us the answer outright, the existence of a chimpanzee-gorilla hybrid would settle the question entirely. Chimpanzees and humans split from one another approximately 5-7 million years ago and from gorillas maybe 8-9 million years ago. This means that chimpanzees and humans are more closely related to one another than chimpanzees are to gorillas. If chimpanzees and gorillas could hybridize, it’s more than likely that humans and chimps could, too.

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1 Du Chaillu, P.B., 1861. Explorations and Adventures in equatorial Africa: with accounts of the manners and customs of the people, and of the chase of the gorilla, the crocodile, leopard, elephant, hippopotamus, and other animals. Harper & Brothers.

2 Elaine , S. “Koolakamba”, Primate Info Net Banner, University of Wisconsin System Board of Regents, available at:

3Stark, D., Schneider, R. and Kuhn, H.J., 1967. Neue Ergebnisse der Primatologie.

4Engel, R. and Petropoulos, A. (n.d.). “In Search of the Mystery Apes of Bili Forest”,, NBCUniversal News Group, available at:

5Hicks, T.C., 2010. A chimpanzee mega-culture?: exploring behavioral continuity in Pan troglodytes schweinfurthii across northern DR Congo. Universiteit van Amsterdam.

6von Koppenfels, H., 1881. Late Explorations in the Gaboon. The American Naturalist, 15(6), pp.447-453.


7Cochran, G. (2018), “So I’m saying there’s a chance”, West Hunter, 26 November, available at:

8Barash, D.P. (2018), “It’s Time to Make Human-Chimp Hybrids – Issue 58: Self”, Nautilus, 8 March, available at:

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