Bili Apes: The Largest Chimpanzee Ever?

Chimpanzees belong to the order of Primates, which is estimated to include more than 500 species. There are 5 species in the great ape, or Hominidae family, including chimpanzees, gorillas, orangutans, bonobos, and humans. Chimpanzees have a number of features in common with humans. They have human-like features and body structures, complex societies, and they exhibit a wide range of emotions. Most chimps are not as large as humans on average, but some have been reported to be as large as small gorillas — most notably, the Bili apes. Are they the largest chimpanzees ever? Keep reading to find out.

The Average Chimpanzee

Chimps are sexually dimorphic, with male chimps typically larger and stronger than females. When standing upright, chimps generally measure between 3 and 5.5 feet tall, although there are variations depending on subspecies and between individuals.

Males weigh between 74 and 154 pounds, while females weigh 57.3 to 110 pounds. In captivity, chimpanzees can be much larger since they eat more and are less active. Some sources indicate males in captivity can reach up to 176 pounds and females can reach about 150 pounds.

What Are the “Lion Killer” Bili Apes?

In the early 2000s, sensational reports suggested that larger chimpanzees with gorilla-like qualities lived deep in jungles in the Bili-Uéré region of the Democratic Republic of Congo. The chimpanzees from the area became known as “Bili apes.” They were said to be the size of a grown man and to walk on two legs. Sources claimed these apes also howled at the moon, nested like gorillas, and feasted on predators such as lions.

Interest in Bili apes led researchers to attempt to discover this mysterious ape. Expeditions into the jungle determined that Bili apes were unlikely to be a unique chimpanzee subspecies as many had thought. DNA testing in 2003 proved that Bili apes were the same species as other apes in Central Africa, Pan troglodytes schweinfurthii, or the Eastern chimpanzee.

Bili Ape Behavior

However, there are unique aspects of this chimpanzee population that distinguish them from other Eastern chimpanzees. According to some animal experts, a few of the stories about Bili apes are true. However, researchers found that most of the claims about their behavior, such as howling at the moon and preying on lions, were greatly exaggerated.

Ground Nesting

Bili apes do like to build ground nests as gorillas do. They use interwoven branches and saplings and bend them forward or down into a central bowl. Yet, they build nests in trees as well. Ground nests are often found beneath or around areas where there are tree nests.

Tool Use

Bili apes have also been shown to exhibit sophisticated tool use. They select differently-sized sticks depending on the task. For example, scientists found they used longer sticks to extract epigaeic driver ants and shorter sticks to draw out ponerine ants and harvest stingless bee nests in the trees. They used thicker sticks to reach into underground stingless bee nests. Bili apes also use smashing techniques to open termite mounds and hard-shelled fruits.

Specialist Diet

The Bili ape diet consists of fruits or fruit trees such as figs, similar to the diet of other chimps. However, Bili apes eat a different species of termites than other chimpanzees. They do not eat termites that belong to the Macrotermes genus, although other apes favor them. They have also been observed hunting for odd prey, such as tortoises and African giant snails, which they smash open to consume. The “lion-killer” claim is believed to stem from an observation of an individual eating meat from a lion carcass.

Interest in Humans

When confronted with humans, Bili apes not only show a general interest in them, but they may even approach people. Researchers report these chimps sometimes come face to face with humans, stare intently for a period, and then move away. There is usually no fear or aggression like in many other primates.

Are Bili Apes the Largest Chimpanzees in the World?

As noted previously, some early reports claimed Bili apes could reach heights of fully grown humans. There were even some claims that Bili apes could reach up to 6.5 feet tall. However, scientific studies have found that their size is within the normal range for Eastern chimpanzees. There is no verified evidence of such extreme heights. In fact, Eastern chimpanzees are generally smaller than other chimpanzee species, reaching an estimated standing height of no more than 5 feet tall and only weighing between 66 and 88 pounds.

Bili apes were documented occasionally walking on two legs as in the stories, which would make them appear taller than usual to observers. However, their gait was said to be awkward and stilted, similar to other chimps. Chimpanzees most often use their knuckles to walk on all four limbs. They are unable to walk bipedally for very long due to the way their thigh bones fit into their hip sockets. So, it is highly unlikely that Bili apes could walk on two feet for extended periods.