Chimpanzees belong to the taxonomic family of great apes, also called Hominidae. This family is composed of seven living species classified in four genera. Great apes are tall and have no tail, they are characterized by a large brain. The smallest is the bonobo (average of 30-40 kilograms in weight) and the tallest is the gorilla (up to 140-180 kilograms).
The males are generally taller and stronger than the females. Great apes are largely quadrupedal but can also walk upright on short distances. They are very agile with their hands, which they use to find food, make their nests and even in some cases use tools. Most species are omnivorous, but fruits are their favorite food.
Great apes all have a gestation of 8-9 months and mothers usually give birth to a single offspring. Sometimes, as with humans, twins are born. Just like human babies, great ape newborns need the constant care of their mothers for long periods of time. Females give birth to one offspring every few years but the youngsters remain with their mothers until the age of eight to thirteen.
Chimpanzees, bonobos and gorillas live in family groups, orangutans live alone and only come together for mating.
All great apes are very close genetically to humans. Chimpanzees and bonobos share up to 98,5 % of their DNA with humans, gorillas have up to 98 % of DNA in common with us. Orangutans, less closely related, still share up to 96,5 % of their DNA with humans.
The different species
Chimpanzee (Pan troglodytes)
Wild chimpanzees only live in Africa. Chimps can be found in about 21 African countries, mostly in central Africa. They live in equatorial rainforests and African savannas.
Humans and chimpanzees share 95 to 98 percent of the same DNA. Biologically, chimpanzees are more closely related to humans than they are to gorillas.
At Gombe National Park, site of Jane Goodall’s research, adult males weigh between 45 and 55 kilograms. They are about 4 feet tall when standing upright. Females are slightly smaller. Chimpanzees in West Africa and those in captivity may be larger and males can weigh up to 80 kilograms.
Like humans, chimps have opposable thumbs and opposable big toes which allow them to grip things with their feet. Chimpanzees walk on all fours and have longer arms than legs. They are called “knuckle walkers” because they use their knuckles for support. On rare occasions, they are seen walking upright for short distances.
Chimpanzees are diurnal and omnivorous. They eat fruits, nuts, seeds, blossoms, leaves, and many kinds of insects. Sometimes they hunt and eat small mammals such as bushbuck or monkeys. Chimpanzees have a wide variety of tastes and are able to live in a wide variety of habitats, unlike gorillas and orangutans that have narrower diets.
Female chimpanzees have a gestation of eight months and give birth to one newborn at a time, although sometimes twins are born. Dependent young and their mothers are together for the first seven to ten years of their lives, learning how to groom, make nests in trees, find food, and use tools. Females give birth every four to five years. When a mother dies, her orphaned offspring may be unable to survive alone and often older siblings adopt their orphaned brothers or sisters, and occasionally abandoned infants are adopted by chimps not related to them.
Infant chimpanzees have a white tail tuft that disappears after their childhood. They also have a white face, which make young chimpanzees very recognizable.
Chimpanzees in the wild rarely live longer than 50 years. Captive chimps can live more than 60 years.
… and behaviour
Chimpanzees communicate much like humans do — by kissing, embracing, patting on the back, touching hands, and tickling. Chimpanzees even laugh when they play. When chimpanzees are angry or frightened their hair stands on-end.
One of the chimpanzee vocalizations is the “pant-hoot.” Each individual has his or her own distinctive pant-hoot, so that the chimp can be identified with precision by other members of the community.
Chimps regularly groom each other and this helps establish relations within the community and calms nervous or tense chimps.
Male chimpanzees show their power in “displays.” Their hair stands on end so they look bigger, they scream, stamp their feet, and go on a tear, dragging branches, or hurling rocks. This may scare other chimpanzees and keep them from picking a fight.
Chimpanzees and other species, including some types of birds, make and use tools. For a long time, scientists thought human beings were the only ones capable of making and using tools. It turns out that Chimpanzees use more tools for more purposes than any other creatures, except for humans. Different chimpanzee groups use tools in different ways. Chimpanzees of the Tai Forest in Cote d’Ivoire have been observed cracking open nuts with rocks, for example, while this behavior has not been seen with the chimps at Gombe.
Chimpanzees are endangered species. There are currently between 172,000 and 300,000 chimpanzees remaining in the wild. In the 1960’s, their number was estimated at one million individuals. Due to habitat destruction, hunting and human diseases, their population is decreasing rapidly.
The pressure on their habitat is due to forest logging for the timber industry, leaving only patches of the former continuous equatorial forest belt. Mining and other extractive activities also contribute to habitat loss, as roads for access are built, separating the forests in smaller parts and preventing chimpanzees of accessing food sources. The rising human demography is the last factor threatening chimpanzees. Humans cut the forests for agricultural purposes and hunt chimpanzees for commercial meat.
Chimpanzees are not meant to be pets; a full-grown chimpanzee has five or six times the strength of a human being.
Bonobo (Pan paniscus)
The bonobo, Pan paniscus, was previously called the pygmy chimpanzee as it was believed to be a subspecies of the common chimpanzee. It actually is a different species and makes up with the chimpanzee the genus Pan. Bonobos can only be found in the Democratic Republic of Congo, where it is an endemic species in an area of 500 000 km² between the Congo River and the Kasai River.
Like the chimpanzee, bonobos are omnivorous and live in rain forests and swamp forests.
Bonobos are smaller than chimpanzees, ranging 70 to 83 cm in height and 34 to 60 kilograms in weight. Their heads are smaller too, with less prominent brow ridges above the eyes. Bonobos have a black face with pink lips, small ears, wider nostrils and long hair on the top of their head. Youngsters have also black faces, opposed to the white faces of chimpanzee babies. The bonobo also has a slim upper body, narrow shoulders, thin neck, and long legs when compared to the common chimpanzee.
Bonobos live in family groups lead by females who collectively dominate the males by forming alliances. Females use sexuality to control males. Indeed, the sexual behavior of bonobos is very diverse and omnipresent in their lives. Sex is used to appease conflict, to give affection, defines hierarchy and social status, and reduces excitement and stress. It occurs in almost all partner combinations and different positions have been seen. Aggressive encounters between males and females are rare, and males are tolerant of infants and juveniles. In addition, primatologist Frans de Waal states that bonobos are capable of altruisme, compassion, empathy, patience, sensitivity and kindness. All these characteristics give the name of “Hippie Chimp” to the bonobos.
The bonobo eats mainly fruit, but leaves and meat from small vertebrates (squirrels, duikers) and invertebrates also form their diet.
Bonobo population is estimated between 29 000 and 50 000 individuals. In the last 30 years their population is believed to have declined sharply. They are classified as endangered species and figure on the IUCN Red List. Major threats are habitat destruction by human populations and activities as well as commercial poaching. Also the fragile situation of the DR Congo which undergoes frequent war episodes makes conservation of bonobos highly difficult.
Do you know?
Two bonobos at the Great Ape Trust (USA), Kanzi and Panbanisha, have been taught how to communicate using a keyboard labelled with lexigrams (geometric symbols) and they can respond to spoken sentences. Kanzi’s vocabulary consists of more than 500 English words and he has comprehension of around 3,000 spoken English words.
Gorilla (Gorilla gorilla and Gorilla beringei)
Gorillas are the largest existent primates by size. Two species have been identified (Gorilla gorilla – western gorillas, and Gorilla beringei – eastern gorillas), with two subspecies each.
They inhabit central African tropical or subtropical forests and live most of the time on the ground. They do only rarely climb in trees as they are to heavy.
Gorillas have a patchy distribution. Gorillas can be found it various elevations, with the mountain gorillas that can be found at altitudes ranging from 2 200 – 4 300 meters in the montane cloud forests of the Virunga Volcanoes. Lowland gorillas live in dense forests and lowland swamps and marshes as low as sea level, with western lowland gorillas living in Central West African countries and eastern lowland gorillas living in the Democratic Republic of the Congo near its border with Rwanda.
Gorillas, like all other great apes are threatened. Existing population of western lowland gorillas is estimated at over 100 000 in the wild and 4 000 in zoos. Eastern lowland gorillas have a population of only 4 000 in the wild and 24 in zoos. Mountain gorillas are the most severely endangered. Their population is estimated to only 640 left in the wild and none in zoos. Humans and their activities are gorilla’s major threat.
Gorillas are the largest primates existing today. Males weigh 135 to 180 kg and female adults between 68 and 113 kg. Males can reach 1,7 to1,8 m in height, while females are smaller. Gorillas have a large skull, with a mandible that protrudes farther than the maxilla. Also, adult males have a prominent sagittal crest, a bone crest on top of their skull.
All eastern gorillas have black fur, although mountain gorillas have the darkest and the thickest hair of all. Western gorillas can be brown or grayish with a reddish forehead. Eastern gorillas are stronger built, less slender, have a longer face and a broader chest compared to their western counterparts.
A silverback is typically more than 12 years of age, and is named for the distinctive patch of silver hair on its back, which comes with maturity. Silverbacks also have large canine teeth which also come with maturity.
The diet of the gorillas varies with the species. Mountain gorillas primarily eat bamboo. They mostly eat foliage, such as leaves, stems, pith, and shoots, while fruit makes up a very small part of their diets. Eastern lowland gorillas have more diverse diets, which vary seasonally. Leaves and pith are commonly eaten, but fruits can make up as much as 25% of their diets. Eastern lowland gorillas will also eat insects, preferably ants. Western lowland gorillas depend on fruits more than the others and have less access to terrestrial herbs. Termites and ant are also eaten.
A gorilla’s lifespan is between 35 and 40 years, although zoo gorillas may live for 50 years and more.
Females become mature at 10-12 years, and males at 11-13 years. When gorilla females are in estrus it is much less visible than for chimpanzee or bonobo females. The gestation period is 8 and a half month and a female gives one offspring at a time and has an interbirth interval of four to five years. Gorillas mate all year round. Gorilla infants are vulnerable and entirely dependent on their mother. The gorilla offspring start breaking contact with their mother after five years, but only for short periods. When they are one year old, the distance and frequency of separation increase, until they regularly spend time away from each other when the young reaches two years. They enter their juvenile period at their third year, and this lasts until their sixth year. At this time, gorillas are weaned and they sleep in a separate nest from their mothers. This is the time the females ovulate again and can become pregnant again.
Gorillas live in groups called troops generally made of one adult male or silverback, multiple females and their offspring. Multiple male troops have also been observed. Both males and females tend to emigrate from their natal groups. For mountain gorillas, females disperse from their natal troops more than males. The silverback is the center of the troop’s attention: he decides, determines the directions and makes decisions about the daily schedule. He’s leading the others to feeding sites and takes responsibility for the safety and well-being of the troop. The younger males (between 8 and 12 years of age) are called blackbacks, as they’re lacking the silver back hair and may serve as backup protection.
The gorilla’s society is well defined and is based on the bond the silverback has with its females. Bonds are maintained by grooming and staying close together. The male generally has a strong bond with the females, whereas the females between themselves have varying relationships. If females are maternally related, they tend to be friendly to each other otherwise they commonly act aggressively towards each other.
Females may fight for social access to males. It is important for gaining mating opportunities and protection from predators and infanticidial outside males. When a silverback takes over a harem of another silverback (when this one is too old or too weak to lead the group because of illness) infanticide can occur (killing offspring). After infanticide has happened, females go in estrus again and can get pregnant faster from the new leader. When a silverback dies, either the males fight for dominance, or the group dislocates and the females join other troops.
If being disturbed, he will start to threat by loud drumming on his chest. This usually stops with just being a threat. The drumming on the chest with the hands and emitting loud cries is the way for gorillas to chase away enemies, but also to show others who is the boss.
A gorilla won’t do any harm unless you look him straight into the eyes as he will feel threatened then.
Gorillas are considered highly intelligent. A few individuals in captivity, such as Koko, have been taught a subset of sign language. Like the other great apes, gorillas can laugh, grieve, have “rich emotional lives”, develop strong family bonds, make and use tools, and think about the past and future.
Do you know?
- The closest relatives of gorillas are chimpanzees and humans, all of the Hominidae having diverged from a common ancestor about 7 million years ago. Human genes differ only 1.6% on average from their corresponding gorilla genes in their sequence, but there is further difference in how many copies each gene has.
- Gorillas rarely drink water because they receive their water intake from the lush vegetation and the morning dew. Yet, some mountain and lowland gorillas have been observed drinking.
- For years, the gorillas that have been studied most in the wild have been the Mountain gorillas. It’s only in the last decade that there has been research done on the Western lowland gorillas as well. This research has shown that there are many differences between Mountain gorillas and Western lowland gorillas. So for instance, based on studies done on Mountain gorillas it was assumed that all gorillas are afraid of water. Recent research though shows that Western Lowland gorillas often wade in shoulder deep water and eat water plants. The splashing of water during sessions where they want to impress others seems to have an important social function.
Orangutan (Pongo pygmaeus and Pongo abelii)
Orangutans are the only great apes living outside of Africa. They inhabit Indonesia’s luxurious rainforests and are formed of two separate species: Pongo pygmaeus or Bornean orangutan and Pongo abelii or Sumatran orangutan. These two species are the only surviving species of the Ponginae subfamily. This family included other species in the past, such as the largest known primate Gigantopithecus whose size is estimated to reach 3 meters in height.
“Orangutan” means “person of the forest” in Malay and Indonesian.
Orangutans spend nearly all of the time in trees, but like other great apes, their habitat is being destroyed. In particular, the forests are logged for palm tree plantations. They are also victims of pet trade.
The Bornean orangutan is classified as endangered and Sumatran orangutans as critically endangered. In fact, estimates between 2000 and 2003 found that 7 300 Sumatran orangutans and between 45 000 and 69 000 Bornean orangutans remain in the wild.
Orangutans have a reddish-brown fur. Although orangutans in Borneo differ in color from their counterparts in Sumatra. Their hair is more red-brown to almost black, while the animals of Sumatra are more light orange and have coarser hair. They are perfectly shaped for living in trees: their arms are about twice the size of their legs and are extremely strong. Also their hands and feet are perfectly made for climbing. Their fingers and toes are so long that they have to withdraw them while walking. Unlike gorillas and chimpanzees, orangutans are not true knuckle-walkers, and are fist-walkers instead.
They can grow to 127 cm for females and to 175 cm for males. They weigh between 45 kg (females) and 118 kg (males). The sexual dimorphism, the fact that males and females do not look the same and can be easily identified, is also visible at the male’s throat pouches, which allow him to make loud calls (they can be heard in the jungle till up to 17 km away). They also have large cheek flaps that show their dominance, attract females and intimidate rivals.
Younger males do not have these characteristics and resemble adult females. Only resident males, which are dominant on a certain territory over food and females, and who have a higher testosterone level, develop cheek pads, they are called flanged males. Unflanged males do only develop these features in the absence of a resident male.
Orangutan’s diet is essentially fruit-based. However, they also eat vegetation, bark, honey, insects and bird eggs.
For reproduction, males, who mature at around 15 years of age, go in search for females in estrus. Resident males may form consortships with females that can last days, weeks or months after copulation. Gestation lasts for 9 months, and females give births to one offspring at a time and only every eight years. This is the longest interbirth interval among the great apes! The first offspring’s born when the mother is between 14 and 15 years of age. Females do most of the caring and socializing of the young and often get help from the older offspring.
The young is totally dependent of his mother until the age of two. From two years on, the climbing skills of the young improve and he starts travelling the canopy, socializing with other orangutans. Their lifespan can reach over 30 years in the wild as well as in captivity.
Orangutans are the most solitary of the great apes, with social bonds occurring primarily between mothers and their dependent offspring, who stay together for the first two years. Orangutans are the least social of the great apes, but individuals do commonly interact. Although the animals are solitary they still maintain an extensive social contact with neighbors by smell or sound. This way the orangutan differs from all other great apes that live in permanent groups with a strong hierarchy.
Orangutan societies are made up of resident and transient individuals of both sexes. Resident females live with their offspring in defined home ranges that overlap with those of other adult females, which may be their immediate relatives. One to several resident female territories are encompassed within the home range of a resident male, who is their main mating partner. Transient males and females move widely. Orangutans will also form traveling groups with members moving between different food sources. These groups tend to be made of only a few individuals. They also tend to be consortships between an adult male and female.
Orangutans are among the most intelligent primates; they use a variety of sophisticated tools and construct elaborate sleeping nests each night from branches and foliage. Evidence of sophisticated tool manufacture and use in the wild has been reported. Orangutans developed a tool kit for use in foraging that consisted of both insect-extraction tools for use in the hollows of trees and seed-extraction tools for harvesting seeds from hard-husked fruit.
Also, wild orangutans in Borneo were reported using leaves to amplify the kiss squeak sound they produce. This tool was an acoustic communication tool used for sound amplifications to deceive the listener into believing they are larger animals. Furthermore, a study in 2008 of two orangutans at the Leipzig Zoo showed orangutans are the first nonhuman species documented to use ‘calculated reciprocity’ which involves weighing the costs and benefits of gift exchanges and keeping track of these over time.
Do you know?
The Sumatran orangutan genome was sequenced in January 2011. Following humans and chimpanzees, the Sumatran orangutan has become the third species of hominid to have its genome sequenced.
Despite their quite fearsome looks they are actually very peaceful animals who will never attack other animals or human beings. If being challenged, the orangutan will rather leave the place peacefully than start a fight.