have opposable thumbs and thumb-like big toes. They can grip with
both their hands and their feet when climbing.
chimp's arms are longer than its legs, an adaptation that helps
them move easily through the treetops. The process of swinging
through the trees from branch to branch is called brachiating.
usually walk on their knuckles and the soles of their feet. They
also are capable of walking on two legs.
use and manufacture tools.
Chimps will prepare objects that are used as tools. They may strip leaves from a twig or remove the bark from a larger stick. Leaves may be chewed to make them more absorbent.
Chimpanzees found in different parts of Africa have developed different traditions of tool use. For example, chimps in West Africa use stones as hammers to open nuts. This type of behavior has not been observed among chimps in East Africa.
the evening, chimpanzees build sleeping nests of twigs and branches
bent together. Nests are built in trees usually at a height of
3 - 30 feet.
have determined that tool use and nest construction are taught
to younger animals by observing the older, more experienced individuals.
These skills appear not to be instinctive.
Social Structure & Behavior
note: Chimpanzee behavior and society is very complex. All of the
information cannot be covered in a few short pages - volumes have
been written on chimpanzee behavior. The following information simply
provides an overview of the behavior and social structure of these
fascinating and highly intelligent animals.
are diurnal but sometimes move about at night. They feed for 6-8
hours during the day and forage over a distance of 1-10 miles or
more. Peaks of activity occur in the early morning and between around
3:30 to 6:30 p.m.
chimpanzee community is a fusion-fission society. The society is
extraordinarily complex: without a high level of intelligence, chimpanzees
would not be able to cope with the uncertainties and tensions so
often engendered by the constantly changing social environment," (Goodall-Gombe 147).
populations are divided into communities of males and females that
share a home range.
Communities can range in size from 20-100 individuals
of all age classes. Range size in forest and woodland areas averages
7.5 square miles (12 sq. km). Savannah ranges are larger - 75-348
sq. miles (120-560 sq. km).
of either sex have nearly complete freedom to come and go from a
community as they wish, but the overall "patterning" of
a chimp community is believed to be greatly influenced by the presence
or absence of a cycling female. Chimps will associate with each
other for varying lengths of time, depending on the intensity of
relationships to other chimps, reproductive status and the distribution
of needed resources. Each individual has its own social contacts.
community is divided into subgroups or parties. Only rarely, if
ever, do all members of a community congregate in one place. Except
for females who are raising offspring, these subgroups are generally
unstable and can fluctuate often. The temporary subgroup's composition
changes frequently, as well, sometimes within a matter of hours
or days. They can include any category of animals - all adult males,
all adult females, both sexes, adults and young, or all young. Party
or subgroup size is affected by the sex, age, and reproductive status
of the individuals in the party, and may range from 2 - 14 animals.
members may meet and form a subgroup only when they have a common
interest, such as a food source. Other community members are together
often in subgroups, and strong bonds develop between some of them.
The single exception to this fluctuation in party composition is
a mother and her dependent offspring, who researches have found
to be together at all times.
are thought to be territorial. Aggression can occur between two
communities. A group of two or more males of a community will venture
out about every four days into the margins of their home range,
seemingly to "patrol" the area. If they encounter a neighboring
community comprised of a larger number of adult males, they will
withdraw to the safer portions of their own territory. If they hear
or see a group of similar size and number, both sides will act in
a way to make themselves appear stronger and larger. This can include
throwing rocks and beating tree trunks, as well as loud, savage
this display, both groups will usually withdraw to the safety of
their own ranges. If the patrolling males encounter a lone stranger
or a solitary female with her offspring, the males will chase and
even attack. With the exception of a female in heat, researchers
have found that male chimps of a community will tolerate no foreign
chimpanzees, regardless of sex, within their range.
between communities is generally much more serious than aggression
between the members of the same community. Encounters and conflicts
between communities can result in serious injuries or even death,
whereas conflicts between members of the same community rarely last
even a few minutes.
community has a dominant male leader, known as the alpha. The rest
of the hierarchy falls into levels of high-ranking males, middle-ranking
males and low-ranking males. Powerful alliances and coalitions also
exist among both females and males. These coalitions are particularly
important when a male needs support to attain or maintain his rank
within a community.
her research, Jane Goodall has determined that a male's rank is
not based on physical strength alone. Biologists have observed that
some dominance struggles involve such important traits as self-confidence,
initiative, resourcefulness and persistence.
are nearly always some young, low-ranking males waiting for an opportunity
to improve their status within a community if they detect an alpha's
is in ill health or aging, or if he loses an ally. By repeatedly
challenging a higher-ranking male, another male is often able to
assume a higher position over an extended period of time.
males work their way up the ranks by first challenging the females
of the community, and then the senior males. Males usually reach
their ultimate spot in the overall hierarchy between age 20 and
26. However, after a male has reached about 30 years of age his
status drops, sometimes gradually and sometimes suddenly.
within a community may occur between males in a struggle for social
position or when one family member defends another. Frustration
also may cause aggressive behavior. When an individual has been
attacked or threatened by an animal of higher rank that he isn't
able to challenge within the hierarchy, he may take his frustration
out upon some lower-ranking individual in the area.
cannot always be ranked in a clear-cut dominance hierarchy. However,
several observations have shown that a hierarchy of levels may exist
among the females in a community, similar to the levels seen in
males. There are often females " who are clearly very high
ranking (one of whom often emerges as alpha) and others who rank
very low; the remainder fall into a middle-ranking class."
A female's rank is greatly influenced by the "nature of her
family" and the presence of certain family members when she
encounters another female (Goodall-Gombe 437-439).
are often said to be "more gregarious" than females and
prefer each other's company, except when females are in estrus.
Females tend to "spend most of their time with their own offspring
- except when cycling, at which time they become very sociable,"
such as posture, touching and grooming, sound, and facial expressions
are used to reinforce social hierarchies.
"have highlighted striking similarities in the behavior of
chimpanzees and man, notably in nonverbal communication patterns,"
(Goodall - Shadow 284).
most common adult call, consists of a "series of hoo sounds
connected by audible intakes of breath, gradually getting louder
and usually ending with waa sounds also connected by panting intakes
of breath," (Goodall - Shadow 273). The pant hoot is used to
maintain contact between the scattered subgroups of a community.
Chimps can recognize each other by the sound of individual calls.
behaviors are used to reaffirm the social status of the individuals
involved. The pant-hoot and gestures such as presenting and crouching
nervous animal may hold out a hand toward the higher-ranking animal,
or bow to the ground and crouch submissively with a down-bent head.
The dominant animal may then give the lower-ranking animal a reassuring
pat or touch, or even hold its hand.
may also use high- or low-pitched grunts to communicate. "A
subordinate chimpanzee is likely to pant-grunt as he approaches
a superior during a greeting or after being threatened or attacked.
If the superior behaves at all aggressively during the interaction,
pant-grunting quickly becomes squeaking or screaming and the chimpanzee
grins," (Goodall - Shadow 276).
frightened or excited chimpanzee may touch or embrace a nearby chimpanzee
as a form of reassurance.
grooming is extremely important in chimpanzee societies.
behaviors/gestures may include: hitting, kicking, scratching, hair
pulling, biting, stomping, and dragging. After a quarrel, the "vanquished"
will often approach his or her attacker, crouch, "weep",
and sometimes hold out a hand. The superior animal will then "comfort"
the animal it attacked by touching, embracing, or 'grooming' him
or her (Goodall/Grzimek 475).
Chimpanzees, like nearly all social animals, may act out disputes with threatening gestures or sounds. This behavior prevents direct combat and possible injury. Males, and occasionally females, may "display" by charging across the ground or through the trees while swinging or dragging branches, throwing stones or sticks, and stomping about. Such displays are important to males in attaining a position of high rank (Goodall/Grzimek 475).
may occasionally arise between a male and female if the female is
"unwilling to follow them in the early phase of courtship".
Females are sometimes attacked violently for "reasons not clear
to us" (Goodall/Grzimek 475).
are not always engaged in aggressive behaviors or displays. Chimpanzees
also "exhibit a large measure of care, sympathy, and helpfulness
towards conspecifics. Usually such behavior pertains to family members,
but it will also happen that adults not related to each other will
risk their lives for those in danger" (Goodall/Grzimek 481).
of a chimpanzee community have been seen embracing, kissing, touching,
and holding hands after a period of separation (Goodall/Grzimek
Hear other chimpanzee vocalizations: Food Bark, Bronx Cheer
Breeding and Care of Young
in both sexes occurs at about 7-8 years of age, but females do not
usually give birth until 13-14 years, and males are not fully integrated
into the social hierarchy until they are 11 - 15 years old.
are capable of reproducing into their 30s and 40s.
great apes have no 'breeding season'. Males are sexually active
at all times. Females have a hormone-controlled cycle usually longer
than 30 days. The chimpanzee estrous cycle is approximately 34 -
37 days in length, but there are tremendous individual differences.
Cycles ranging in length from 22 - 187 days have been observed.
a female chimpanzee comes into heat, or estrus, the skin in her
genital area becomes swollen. This 'sex skin' is maximally swollen
for approximately 10 days. Ovulation occurs near the time of the
last day of maximal swelling.
variety of situations may arise when a female enters estrus. A female
may be mounted by most or all of the males in the community, or
the highest ranking male may try to prevent others from mating -
especially during the last 3 or 4 days of the cycle, when the probability
of conception is the highest (Goodall/Grzimek 464).
are not always promiscuous. A male may form a short-term relationship
with a female in estrus and prevent lower-ranking males from mating
with her. Male-female pairs may also establish a temporary consortship
for up to 3 months. The pair will leave the vicinity of the community
and mate only with one another. Consortships are often an effective
means for lower-ranking or disabled males to successfully mate.
lasts 7.5 months, and females usually give birth to one young that
will remain with her from 6 to 10 years.
are generally tolerated by all members of the community. Females
may carry or comfort infants other than their own. Males are usually
tolerant of infants and may pat, touch, groom, play with, comfort,
or embrace infants.
the first few months of their life, young chimpanzees are in almost
constant contact with their mothers. Babies less than 5 months of
age are "normally protected by their mothers from all contact
with other chimpanzees except their own siblings. Infants from the
age of 3 months onward often reach out to other chimps sitting nearby,
but usually their mothers pull their hands quickly away" (Goodall
- Shadow 148).
play begins with mother-infant interactions after about 3 months
of age. Play may include the mother bouncing the baby on her hands
while she lies on her back, mother and infant mouthing each other,
play faces, and laughing.
will begin to try solid foods between 4 and 6 months of age.
the first 6 to 10 months, infant chimps travel almost exclusively
in the ventral-ventral position (clinging to their mother's belly).
at 12-16 months of age "have about as much understanding as
a human child of about the same age" (Preuschoft 396).
1 year of age, traveling in the ventral-ventral position accounts
for about 74% of the travel time (Fulk 26).
play, which consists of jumping, tumbling, running, and slapping
inanimate objects, is very common after one year of age.
chimps may begin to engage in social grooming by infrequently grooming
their mother during their first year of life. The frequency of social
grooming increases gradually and accounts for about 2 - 3% of a
2 to 3 year old infant's time (Fulk 28).
may practice building sleeping nests at an early age. Constant practice
helps ensure that a youngster will be skilled at nest making by
the time he or she is 4 or 5 years old and ready to sleep on his/her
chimps also "practice" using twigs and sticks for eating
age 2, riding on the mother's back is the predominant mode of travel
for young chimpanzees. By 3 years, their travel is much more independent.
time that young chimpanzees spend in contact with their mother decreases
over several months. Generally speaking, by 2 years of age, young
chimpanzees spend 20 -30% of their time with their mothers (Fulk
chimpanzees engage in social play quite frequently. By 3 years of
age, the young chimp will be more likely to engage in play with
peers. Mother-infant play becomes uncommon after 3 years of age.
chimps will often build their own sleeping nests during their final
year of suckling. However, they will continue to share a sleeping
nest with their mother until a new sibling is born.
chimps are gradually weaned around 4-5 years of age, as their mother
the wild, chimps will usually give birth every 5 or 6 years. Also,
chimps will continue to associate with their mothers for at least
3 to 4 years after the birth of a sibling. Even 5-year-old captive
chimps have been observed to spend 10 - 25% of their time in contact
with their mothers.
bonds usually last for a lifetime.
adolescence, females tend to move to a new community and seek acceptance,
but males usually stay with the community they were born into.
males begin to venture out on their own more when they are 8-9 years
old. While an adolescent female tends to "plunge into the social
life of the community," an adolescent male will tend to become
a "more peripheral member" of the community (Goodall -
Gombe 168). "A male will associate with other conspecifics
and travel around with them. He will maintain 'ties' with his family
and finds fresh strength among them in his struggle for rank,"
the onset of the first estrus at 9-10 years of age, an adolescent
female will begin to venture outside of her family group. A female
may transfer to another group permanently or she may form a family
of her own in her original home community (Goodall/Grzimek 465).
giving birth to her first infant, the female typically becomes less
gregarious. As a female gets older, she demonstrates a gradually
increasing tendency to spend time with family members only,"