Chimpanzees represent our closest living relative, sharing 98% of our genetic DNA. But chimpanzees (Pantroglodytes) are one of only two species in the genus Pan, the other being the bonobo (Panpaniscus), and we’re equally closely related to both species – evolutionary biologists believe that humans, chimps and bonobos shared a common ancestor around 7 million years ago.
It was once thought that chimpanzees and bonobos were subspecies (known as the common chimpanzee and the pygmy chimpanzee), but they are now recognised as two distinct species.
Both chimps and bonobos are found in sub-Saharan Africa, and it was once thought that chimpanzees and bonobos were a single species, but they are now recognised as two distinct species, geographically separated by the Congo river. The chimpanzee is found north of the Congo river and is split into 4 sub-species; the bonobo lives south of the Congo river and has not been split into any sub-species.
As a highly adaptable species, chimpanzees inhabit a range of habitats, including tropical rainforest, montane rainforests at altitudes of up to 3000m, swap forests, less densely vegetated forest-savannah mosaics, and even dry savannah.
The longest recorded lifespan for a chimpanzee in captivity is 62, though a less reliable record exists of a female living until 78.
Chimpanzee lifespan in the wild is harder to gauge, but a recent study of 306 chimps at Ngogo in Uganda’s Kibale National Park showed the average life expectancy to be about 33 years. This is nearly twice as old as has been found for other chimpanzee groups, and about the same as the average lifespan of human hunter-gatherers.
But the Ngogo group is not a typical one. Unlike other groups studied, it inhabits a productive, healthy forest with low levels of human disturbance, so it might be a more accurate reflection of natural chimpanzee lifespan.
Toxoplasma gondii is a tiny single-celled cat parasite that also infects a range of other mammals and birds as intermediate hosts, forming cysts in their brains and other organs. These hosts must be eaten by a feline if the parasite is to complete its life-cycle, and research in Gabon has shown that infected chimps develop an attraction to the smell of leopard urine.
It’s possible that this morbid attraction to the chimp’s only natural predator is a side effect of having cysts in the brain, but the latest research suggests it’s caused by the parasite itself. This is because the same effect isn’t observed with the urine of lions or tigers, neither of which prey on chimps.
That would mean the parasite is directly manipulating its chimpanzee host into increasing its chances of being killed by a leopard, enabling the parasite to complete its own life cycle.
Do chimpanzees live in groups?
Chimps live in vast social communities, consisting of up to about 100 individuals and comprising several family groups. They have strict hierarchies, with one dominant alpha male.
Females will reach reproductive maturity by age 13 and can give birth at any time of the year, usually to one baby. The infant will cling tightly to its mother’s fur, and then takes rides on her back until two years of age.
Chimpanzees are one of the few animals that are known to use of tools. This includes the use of sticks to retrieve insects from the leaf litter, stones to open up appetising nut contents and leaves to soak up drinking water.
Travelling chimps use more tools than sedentary chimps
A study in 2016 discovered that wild chimpanzees are more likely to use tools if they travel further on a regular basis. Some chimps tend not to travel more than 2km from home in a day, while others will move up to 10km per day, and the researchers found that the regular travelers used more tools of a wider variety.
This also ties in with what we see in other great apes – gorillas and orangutans rarely travel far and rarely use tools, wheras bonobos travel similar distances to chimps and use a similar set of tools. Modern hunter-gatherer humans walk up to 11-14km per day, and they fit the pattern by using a much wider variety of tools than any of our great ape cousins.
The authors of the study even suggested that travel could have been one of the key driving forces behind the early development of tool use in prehistoric humans.
Chimps can be very aggressive. Groups of males will plan and execute attacks on other chimps, often causing serious injuries and fatalities. Fights for dominance within a tribe can also be brutal and will often end in the death of an ousted male.
Serious, fatal chimpanzee attacks on humans have also been reported. Fatal attacks have normally been on local children who live in or near the forest homes of chimpanzees, and several instances have been reported of chimps kidnapping and eating human babies.
There have been a couple of extremely serious attacks by captive chimpanzees in the US that received widespread media attention. These would undoubtedly have been fatal if the victims hadn’t received urgent medical attention – their wounds were extremely severe, leaving them disfigured beyond recognition. You can find details of their injuries elsewhere online, but it’s not recommended for anybody without a very strong stomach.
How clever are chimpanzees?
As well as using tools, some chimpanzees have even been able to learn basic human sign language. Washoe, a captive female chimpanzee, was able to learn American Sign Language (ASL), with a vocabulary of 350 words.
What do chimpanzees eat?
Chimpanzees are omnivorous, but eat fruit more than anything else. Most of a chimpanzee’s diet comes from our bits of plants (seeds, leaves, roots, resin etc) but they will also eat insects, honey, birds and bird eggs, mammals and even soil.
Most shockingly of all, chimpanzees have been documented hunting other primates, and even committing cannibalistic infanticide.
However, the average chimpanzee diet is mostly fruit and plant matter, with insects and meat contributing just 2% of the total.
Chimpanzees make around 30 different vocalisations. The most common and loudest is the pant-hoot, a long-distance call used for a variety of social reasons, but particularly for keeping in touch with fellow troop members.
One study in Kibale National Park, Uganda, found that males were more likely to reunite with other males on days when they pant-hooted more.
Chimpanzees are enormously strong, estimated to be around four times stronger than a human of a similar size. They can reach speeds of 25mph (40kph) when running, and that’s not even what they’re built for.
Their arms are designed to swing them through the trees, and they have a much higher proportion of fast-twitch muscle fibers, which seems to be what gives chimpanzees their extraordinary strength.
Around the village of Bossou in the Central African country of Guinea, chimpanzees have been observed feeding on cacao pods from human-cultivated plants. They’re after the sweet pulp rather than the seeds themselves, which they either spit out straight away or swallow whole, in which case the seeds come out in the chimp’s faeces.
Sometimes those seeds germinate and so a new cacao plant appears. If the farmer discovers the plant, then they will help it to grow by clearing weeds and cutting down other saplings that otherwise might hinder its development. Chimps don’t create whole new plantations on their own, but their inadvertent seed dispersal enables farmers to harvest a bigger crop than they would without the chimps.