July Primate of the Month — Chimpanzee
July Primate of the Month: Chimpanzee
Chimpanzees are the most abundant of the non-human Great Apes, both in number and geographic range. The four subspecies have a combined population of 172,000-300,000 individuals left in the wild, which occupy a geographic range of 2.5 million km² – an area the size of the Mediterranean Sea!
The most heavily studied ape (both in the wild and in captive research settings), there’s plenty to appreciate about our closest genetic relatives. Humans share 98.8% of our DNA with chimpanzees and bonobos, and further studies into their behavioral patterns and societies can give us a look into what our early human ancestors may be been like.
Take a look below to learn more about the incredible chimpanzee!
The most widespread great ape, the chimpanzee is comprised of four subspecies: Central Chimpanzee (Pan troglodytes troglodytes), Western Chimpanzee (Pan troglodytes verus), Nigeria-Cameroon Chimpanzee (Pan troglodytes ellioti), and the Eastern Chimpanzee (Pan troglodytes schwienfurthii). These subspecies may not have significant physical differences, but are genetically distinct and found in different areas of Western and Central Africa. Check out our March Primate of the Month page to learn more about these different subspecies!
Chimps live in a hierarchical communities of 15-150 individuals, led by an alpha male. Males tend to stick with their natal group, while the females will branch off to other groups in their adolescence. As the larger groups may be unwieldy for travel and foraging, chimps will often split off into smaller groups to collect food or scout new territories.
Among the males, rank is largely determined by the partnerships they form with other males – a game of politics so to speak. Gathering allies gives the males more sway in the group dynamics and help settle disputes. Alpha males are typically quite aggressive, with lots of posturing and displays, in order to keep those below him in line. Females are less dependent on social hierarchy, although their rank may influence their offspring.
Chimps are known to to be highly territorial and will even kill other chimps over territory disputes. Jane Goodall famously witnessed the fracture and subsequent deaths of several of her Gombe chimpanzees in the 70s. They are the only non-human ape to do so.
All in the Family
Chimps are non-monogamous and quite promiscuous. When in estrous, females will often mate with several males, even visiting other nearby troops to mate with their males. Gestation lasts 8 months in chimpanzees.
Chimp mothers form very close bonds with their infants and will keep them close for the first few years of life. Much like humans, chimp newborns are quite helpless and totally reliant on their mums for all food, protection, and warmth. The young will cling on the mother’s belly for their first several months and then graduate to riding on the mother’s back when they become strong enough, usually around the 6-month mark.
The moms will continue to breastfeed babies until about 3 years old, at which point the youngins will be learning to climb and gradually venturing farther away from mom’s watchful eyes. Adolescent females will step in to help nurture the young, which helps train them for when they have their own young. Generally, adult males will have no part in raising the young, although some studies indicate that they may work harder to protect their own suspected offspring.
Due to the tremendous amount of care and effort it takes to raise a baby, females will often have a few years between having babies.
Communication and Language
Much like humans, chimps communicate through vocal calls, grunts, and barks, as well as visual and tactile ways – grooming, hugging, and threat displays. Perhaps the most iconic of the chimp sounds is the Pant-Hoot. These hoots are distinct to the individual and can be used to greet other chimps, signal danger, or notify the troop of nearby food!
In the past, chimpanzees in captivity have been taught different sign language symbols, including the famous Washoe who learned up to 240 different signs!
Habitat, Sweet Habitat
What makes a habitat suitable for chimps? Lots of trees!
Forests provide a significant amount of resources for chimpanzees – from food to shelter to scouting possibilities. Chimpanzees will map out their territory and are able to repeatedly travel to the same areas for food and forage. As chimps are so adaptable to changing environments, they are able to live in different types of forest – swamp forests, montane forests, evergreen, and tropical rainforests, to name a few!
Every night, chimps will fashion themselves a nest of leaves and grasses in the trees to sleep in. Generally, chimps will sleep alone, except for infants and juveniles who will nest up with their mother.
Fruits, Foliage, and other Feasts
Chimpanzees are omnivorous but prefer fruits over other food items. Depending on the season, chimps will munch on leaves, roots, shoots, buds, flowers, seeds, nuts, bark, and tree saps from the plants around them. Even though they lean heavily on the greens, they will consume honey, eggs, insects, and small-medium sized birds and mammals, including monkeys and bushpigs.
Hunting and meat consumption are rare and vary greatly depending on the troop. Significant differences in hunting between wild populations are due to the forest structure, the abundance of animals around, and the size of the hunting party. Chimps in the Ivory Coast, for example, are more cooperative in their hunting practices than in other regions to prevent monkeys from climbing the higher tree canopies, out of the chimp’s reach.
The Right Tools for the Job
One notable aspect of chimp behavior is their impressive use of tools, with examples of this complex object manipulation recorded in both captive and wild populations. Chimps will modify branches, leaves, grasses, rocks, and other natural items to collect different foods and treats. The most popular example is their use of long grasses to “fish” termites from mounds, or honey from beehives. They have also been observed sharpening sticks to snag bushbabies out of trees in Senegal, and other small mammals, and collecting flat stones to crack the tough hulls of nuts and seedpods.
Chimpanzees have long been used in a variety of biomedical research trials – from behavioral experiments to drug testing, including a couple of notable excursions to space! While many chimps were taken from the wild in the former half of the 1900s, labs soon began with their own breeding programs, leading to thousands of individuals in labs around the world. In the USA, chimps were primarily used for Hepatitis research, and later for HIV/AIDS testing.
Fortunately, the popularity of chimps as test subjects has gone down significantly in recent years, with many countries phasing out research and opting for non-invasive experiments, or those using non-animal models instead. In 2010, the European Union passed legislation banning outright the use of great apes in laboratory research. In the USA, the National Institute of Health has been working since 2015 to retire their remaining chimpanzees to accredited primate sanctuaries.
What about the Bonobo?
Bonobos (Pan paniscus), sometimes called Pygmy Chimpanzees, are also part of the Pan family but are genetically distinct from their more numerous cousins, the Chimpanzees. Only found in the DRCongo, these endangered apes stick to smaller group sizes than chimps, with the larger groups hitting 10 individuals.
We will be celebrating the Bonobo in future Primate of the Months so stick around!
Threats in the Wild
Chimpanzees have few natural predators in the wild – except of course, for us. However, the odd chimpanzee – especially infants – has been snatched up by leopards, martial eagles, and pythons. Chimps are hunted by humans for a variety of reasons – to capture babies for the illegal pet trade and for bushmeat. All chimps are protected under the law but lack of effective enforcement and local norms are barriers to widespread chimp protection. As chimpanzees are naturally found in some of the world’s most impoverished regions, financial gains selling off bushmeat or infants into the illegal pet trade may be high and tempting.
Sadly their main threat in the wild is that the “wild” is ever-disappearing as humans continue to cut down, burn, and move into the forests that house chimps. Deforestation not only limits their territory – and we saw earlier how territorial they can be – but can also cut off populations as the forests become more fragmented. As their forest home disappears, they are more likely to come into contact with humans, as they crop raid from farms or pass through settlements to other swaths of forests.
Disease transmission in the wild between humans and chimps is well-documented. In the wild, chimps are susceptible to the diseases that plague humans – ebola, SIV (their equivalent to HIV), even the common cold can be deadly to chimps. It is highly suspected that COVID-19 would have a catastrophic effect on population numbers, you can read more about that here! Due to their genetic similarities to humans chimps (Pan troglodytes) have been used extensively over the last century in biomedical research as well as psychology experiments.
The Future of Chimps - Conservation and Concern
Conservation plans for chimpanzees are no small task to create and implement and must involve stakeholders at different levels – from local to governmental. Many factors play into the future of chimpanzees – from human health and livelihood to forest biodiversity, each of which adds another layer of complexity to the overall issue.
Community sensitization schemes are critical to effective long-term conservation plans as they are often the source for human-chimp conflicts. These outreach programs help unpack the mysteries of apes and offering sustainable ways to mitigate conflict in the communities and forests. Educational programs for local children are another way conservation programs can help ensure the continuation of conservation efforts by instilling a love and appreciation for nature in the youth.
Greater and more effective law enforcement is also critical to the survival of chimps and other great apes. In some cases, former poachers have been converted into rangers or other conservation officers, using their knowledge of the forests to help protect the chimps, rather than poach them. Increasing protection of forests, and improving biodiversity trackers will also help ensure that chimps have access to adequate forest resources. You can learn more about chimp conservation efforts through World Chimpanzee Day 2020!
Don’t miss out on future Primates of the Month!
World Chimpanzee Day: https://www.worldchimpanzeeday.org/
General Info: https://animaldiversity.org/accounts/Pan_troglodytes/
NASA and Jane Goodall Institute: How Satellite Data Changed Chimpanzee Conservation Efforts
Whiten, A., & E. (2007, June 19). Transmission of Multiple Traditions within and between Chimpanzee Groups [Scholarly project]. In Current Biology. Retrieved from https://doi.org/10.1016/j.cub.2007.05.031