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CAPUCHIN TRADITIONS PROJECT |
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 Since 1997, a group of 10 researchers has been collaborating
on a study of traditions in white-faced capuchin monkeys. We have
concentrated our efforts on three behavioral domains: social conventions,
foraging techniques, and interactions with members of other species.
We have worked at 4 different research sites in Costa Rica, which
are ecologically similar and close enough geographically that there
is unlikely to be much genetic variation between sites. The map
indicates the locations of the study groups and sites within Costa
Rica. We have collectively observed these monkeys for over 19,000
hours over a 13-year period: this table gives some details on the
database.
image: Sharon Kessler |
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Much of our work thus far has focused on social conventions:
dyadic social behaviors or communicative behaviors that are unique
to particular groups or cliques. We began this phase of the project
by nominating various quirky social interactions or communicative
signals that we had witnessed, soliciting data on these behaviors
from the researchers at all sites, and subjecting them to a set
of operational criteria that allowed us to classify a subset
of the nominations as traditions.
What is a tradition?: We defined a tradition as "a
behavioral practice that is relatively long-lasting and shared
among members of a group, each new practitioner of the behavior
relying to some extent upon social influence to learn to perform
the behavior." We subjected candidate behaviors to the following
criteria to determine whether they qualified as traditions:
- There must be intergroup variation in the behavior, such
that it is common (i.e. seen at a rate of at least once/100
hours) in one or more group and absent in other groups that
have been observed for at least 250 hours.
- The behavior must be observed to spread through a social
network.
- The behavior must endure in the repertoire for at least a
6-month period.
Five behavior patterns were nominated as likely traditions:
hand-sniffing, sucking of body parts (though this one did not
meet criterion #2, perhaps due to the timing of our field seasons
in relation to the onset of the tradition), and 3 kinds of games.
This chart shows the
distribution of each behavior pattern across the study groups. |
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 Handsniffing:
Two basic variants of this behavior are observed: one in which
the hand was cupped over the nose and mouth, and another in which
the fingers were inserted in the nostrils. At Lomas Barbudal,
it was quite common for the behavior to be mutual, with the two
participants inserting their fingers in one another’s nostrils
simultaneously. The hand-sniffers remain in this pose for several
minutes at a time, sometimes swaying gently as they sniff. Observers
often describe the facial expressions as "trance-like." In
two groups (Cuajiniquil and Station Troop), handsniffing was
often combined with finger-sucking behavior. This photo depicts
the beta female (Squint) sniffing the alpha female's hand.
Click here to
watch a video. (RealPlayer - Free Download, click
here). |
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 Eyeball-Poking:
Since the publication of the original set of articles on capuchin
social traditions, we have been documenting the spread of
a new tradition in Pelon group – eyeball-poking. In
this ritual, one participant inserts its finger in the other’s
eyeball, slipping the finger deep between the eyelid and
the bottom of
the eyeball up to the first knuckle. As in handsniffing,
the pair remains in this posture for up to several minutes,
and often
the one being poked in the eye inserts fingers in the partner’s
nostrils or mouth during the eyeball-poking.
Click
here to
watch a video (RealPlayer - Free Download, click
here).
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 Sucking of body parts:
In this behavior pattern, one individual
inserts some body part of the partner (usually an ear, finger,
or tail-tip) into its mouth and sucks on it for several minutes.
Sometimes the behavior is mutual, especially with tail-sucking.
As in hand-sniffing, the participants are relaxed, often grooming
before the onset of the behavior, and a bit isolated from the
rest of the group.
image: Sharon Kessler |
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Games:
Three behavior patterns were referred to as games, because they
involved 2 roles and occurred in a relaxed social context, often
stemming from slow-motion play wrestling, play biting or grooming
of the mouth. In all of these games, one individual takes an
object (finger, hair, or inanimate object) into his mouth and
bites down hard enough that it is hard to extract. The partner
tries to retrieve the object, sometimes using the other hand,
feet and mouth to pry open the other’s mouth. When the
object or body part has been retrieved, it is reinserted into
a mouth, and the game is usually played for several more rounds.
Sometimes the monkeys switch roles. Three basic variants were
observed:
Finger-in-mouth game: This variant
involves insertion of a finger into the partner’s mouth
(either partner can be responsible for insertion of the finger).
Sometimes this game starts in the context of grooming of the
mouth or a “dental exam.” The biter usually bites
down firmly enough that it is quite difficult to remove the finger,
but not hard enough to draw blood. Sometimes this game is combined
with elements of the finger-sucking behavior described elsewhere.
This variant is observed only at Lomas Barbudal.
The photo sequence alongside this page show Guapo biting the
finger of a juvenile companion, who is trying to retrieve his
finger.
Hair-in-mouth game: In this variant, one individual bites a
large tuft of hair from the face or shoulders of the partner.
The partner may flinch, but does not exhibit much pain. The partner
then typically tries to pry open the mouth and retrieve the hair.
The hair is passed with gentle force from mouth to mouth until
most of it has fallen to the ground. Then one of the monkeys
bites another tuft of hair from the partner so they can continue.
The hair game is observed only at Lomas Barbudal.
Toy game: In this variant, an inanimate object (a stick, green
fruit, leaf, or piece of bark) is passed from mouth to mouth
in the same manner in which the hair or finger is transferred
in the other games. No one consumes the toy at the end. This
is the one game that is seen in multiple sites (Lomas Barbudal
and Curú). This video clip (courtesy of Mary Baker) shows
two males from Bette’s group in Curú, Bud and Angelo,
playing the toy game (though the “toy” -- a piece
of bark -- is very small and difficult to see in this clip).
Angelo is soliciting the game, and Bud is trying to remove the
bark from his mouth.
Click here to
watch a video. (RealPlayer - Free Download, click here) |
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