|
Chimpanzee Grooming
Grooming, the
act of tidying, cleaning, or brushing oneself or another, occurs
in both chimpanzees and humans. In fact, grooming is seen in all
primates, though it is performed differently within each species.
Chimpanzees grooming involves removing pieces of dirt, plants, dried
skin, and insects from the hair of another chimpanzee of off of
themselves. Our own human grooming may involve showering or bathing,
cutting or styling our hair, getting a manicure or pedicure,
cleaning your ears, or maybe even an exfoliating massage.
Even
though there are differences in the way we groom they still achieve
the same purpose of cleanliness as well as relaxation and even
bonding. Think of time when you picked a piece of fuzz or other
small particle from your own or someone else's clothes or hair or how
relaxing it is to have someone rub your back. This is just like
what chimpanzees do!
The most obvious
purpose of grooming in the chimpanzee is the removal of unwanted
debris from their coats. But, during times of relaxation, a
chimpanzee may often be found grooming another chimpanzee or its own
hair. When we want to relax, we often take a bath or get a
massage. Just think, grooming is associated with relaxation in
chimpanzees and in us! Normally, the chimpanzee uses one hand to
hold the hair back while the other hand, lips, or teeth are used to
pick out and remove the unwanted small pieces.
Grooming is a very important social interaction for chimpanzees and
is used to maintain friendly ties among family and community
members.
A chimpanzee may request to be groomed by approaching another
chimpanzee and presenting a part of his or her body for grooming. A
grooming session may include several individuals of different ages
and genders, and can last for a few seconds, minutes, or even
hours! Both chimpanzee and human mothers groom their infants.
In chimpanzees, this is sometimes done to reduce the stress of
infants during weaning (the process of gradually changing the
infant’s diet from the mother’s milk to an adult diet). Can you
remember a time when you were young and something made you
stressed or upset? It is possible that your mom may have
calmed you down through physical contact by rubbing your back or
wiping your tears away. Chimpanzees use grooming to reassure
each other as well. Grooming is used to relax tension from
threats and aggression in chimpanzees and may be used as a way
to make up after a conflict and strengthen the relationship for
the future.
Social grooming in chimpanzees can serve other
functions as well. For example, a chimpanzee who had
previously been groomed by another chimpanzee will
be more likely to repay that favor in the future,
either by grooming or sharing food. This means that
in chimpanzees and in humans, if we do something
nice for another, that individual is likely to do
something nice for us. This is called reciprocal
altruism.
For
humans and chimpanzees, both males and females are involved in
grooming. However, grooming plays a special role in the lives of
chimpanzee males and their dominance hierarchy. Studies show that
large males rely more on physical attacks than other techniques to
dominate other chimpanzees. Small males rely on grooming other male
and female chimpanzees to gain their support and remain in good
standing within the community. This helps the less dominant males
form alliances to guard against larger males. As a result of these
behaviors, smaller males tend to groom more often than larger males
that do not need support from others.
Grooming is a
large aspect of chimpanzee culture. Culture refers to the behaviors
or ways of living of a particular group that can be passed from one
generation to another. Although all humans and chimpanzees groom,
different groups, often located in different parts of Africa, may
perform it differently.
|
 |
One example is
the “social scratch” shown by the Mahale chimpanzees.
The
grooming chimpanzee runs their hand up and down another’s back. This
is usually done with bent fingers and making long movements up and
down. Chimpanzees living in Ngogo also do the social scratch, but
they use straight fingers and make short movements up and
down. These two groups are the only which have been observed
performing the “social scratch”. |
|
 |
Another is called the
“handclasp” seen only in the chimpanzees that live in the Mahale
Mountains. Each of the chimpanzees extends their arms overhead at
the same time and then grasps the other’s wrist or hand. The
opposite hand is used to groom the other chimpanzee. |
The chimpanzees
of Mahale and Gombe make two sounds called lip smacking and teeth
clacking, when grooming other individuals. These sounds are
accompanied by rhythmic lip movements. If a grooming chimpanzee
finds something interesting, the chimp may smack its lips or clack
its teeth and immediately bring its mouth to the object. Although
the chimpanzees of Ngogo sometimes lip smack and teeth clack, they
make entirely different grooming sounds from the chimpanzees in
Gombe and Mahale. The Ngogo sound is called sputtering and they do
not show rhythmic lip movements.
The
chimps at Gombe use leaves to squash small bugs that they pulled
from one another’s coats. Scientists believe the chimps started
doing this for one of two reasons: because the leaves made it easier
to kill the insects or because the chimps did not like getting their
hands messy! After this amazing behavior was discovered in the Gombe
chimpanzees, it was also observed in Mahale and Kibale. Unlike these
chimps, Tai chimps remove the insects, place them on their arm,
smack them with their hand, and then eat them!
The grooming
behaviors discussed here are unique to the particular groups, and,
at first, were seen among only a few chimps but now are seen in
generation after generation throughout an entire chimpanzee
troop. Group members get these skills through a social learning
process. A variety of other cultural behaviors are seen in
chimpanzees.
|
Message from CAC'ers
When
we were in Tanzania, we had the pleasure of getting to watch
chimpanzees grooming each other on more than one occasion.
We could not help but notice how calming and friendly it
seemed. In fact, one time we came upon a group of chimps
sitting on the trail surrounding a female that appeared to
have something stuck in her bottom. A number of chimps
gathered around trying to pick it out for her. Those are
some awfully nice friends and family members, would you do
that for a friend?!
|
|
