Chimpworld: Behavior

-------Wild-------

-Bossou-

Geo. Bossou
Research Team
Chimp. Beh.
Nimba/Diecke
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References
Name of Chimps(PDF)
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Video"Jokro"

-----Captive-----

Zoo in Japan

CHIMPANZEE BEHAVIOR

FEEDING

Chimpanzees are predominantly fruit eating, but they also eat a variety of other foods. So far, we have observed that fruits, leaves, flowers, seeds, pith, bark, gum, sap, mushrooms, algae, insects, honey, bird eggs, owls, and tree pangolins make up the feeding repertoire of Bossou chimpanzees. You can observe below chimpanzees feeding on figs, an important fallback food for the chimpanzees due to it's a seasonal fruiting patterns.

TOOL USE

Chimpanzees make and use a diverse and rich kit of tools and, with the exception of humans, they are the only living primates to consistently and habitually use and make tools.

Subsistence tool use behaviors displayed by the Bossou community:

Nut cracking at Bossou:
Chimpanzees of Bossou are well known for using a stone hammer and anvil to crack open the nuts of the oil palm tree (Elaeis guineensis). Among all the tool use behaviors observed in the wild, nut cracking is probably the most sophisticated performed by chimpanzees. Indeed, this behavior is characterized by the requirement for both bimanual and asymmetric manipulation, which has thus far never been reported for any other tool use behavior observed in the wild.

1. This is an adult female chimpanzee, Jire, who is about to crack nuts using stones. She has carefully selected appropriate stones for the task ahead..

2. She reaches out on the ground below the palm tree for a nut to crack.

3. She then proceeds to place the nut on the anvil stone and with her other hand, she takes her hammer stone and pounds the nut several times.

4. The nut is finally cracked and Jire can gain her reward. The nut contains a kernel, which is very tasty and full of energy. Chimpanzees at Bossou love eating oil palm nuts!

Matsuzawa and colleagues have also been conducting field experiments in an outdoor laboratory, in order to gain more insight into nut cracking behavior, mainly focusing on its acquisition by youngsters (Sakura & Matsuzawa, 1991; Matsuzawa, 1991,1994, 1999; Fushimi et al, 1991; Sugiyama et al, 1993, Inoue-Nakamura & Matsuzawa, 1997). They placed stones and nuts at the top of a hill in the core range of the chimpanzees (outdoor laboratory) and video-recorded the chimpanzees' behavior. They have also experimented with the introduction of a new species of nut (Coula edulis), which is cracked by chimpanzees at Tai and Yeale, Mt. Nimba, in Cote d'Ivoire. This experiment has enabled them to look at the social transmission of a new behavior within the community. The results of these experiments have yielded interesting insights into the transmission of cultural behavior among chimpanzees (Matsuzawa et al, 2001).

Ant dipping at Bossou:
Chimpanzees at Bossou customarily dip for ants using wands (Sugiyama et al, 1988; Sugiyama, 1995). The most common prey species is the safari or driver ant, genus Dorylus. Four species of Dorylus ants (D. kohli (Wasmann), D. lamottei (Bernard), D. wilverthi (Emery) and D. nigricans (Illiger)) have thus far been identified at Bossou by Dr. Brian Taylor. D. molestus, which had previously been noted as present at Bossou by Sugiyama et al (1988), was, however, not identified in the recent samples collected from Bossou. (Refer to Dr. Brian Taylor's website: http://vsb.nottingham.ac.uk/~plzbt/wafants/clog7b.htm for pictures and taxonomic criteria of these species). Safari ants construct underground tunnel nests that are not easily noticeable, unless ants are scrambling at the surface. However, since they use these nests as temporary bivouacs they also move around in large columns on the ground. They can travel in great numbers on the surface of the ground and amongst terrestrial herbaceous vegetation hunting for prey, e.g. earth worms. Ants' nests are usually dug up by hand. Chimpanzees at Bossou have also been observed to dip on migrating ants on the forest floor. Bossou chimpanzees typically hold the wand between their index and their middle fingers and perform a back and forth movement of the wand so as to stimulate the ants' attack of the object. Ants that climb up the wand are typically directly squeezed off and eaten using the lower-lip. But chimpanzees at Bossou also employ another technique, termed the "pull through" technique, i.e. swift and meticulous swiping of the length of the tool from the proximal to the distal end with the hand and ingesting the gathered bundle of ants from the collecting hand. Environmental influences on wand length and technique employed during ant dipping have been uncovered in the Bossou community (Humle and Matsuzawa, 2002 submitted).
Another prey species is the weaver ant (Oecophylla longinoda). Although these are usually eaten directly by hand, Sugiyama also reported the use of a tool in fishing these ants (Sugiyama, 1995).

Termite fishing at Bossou:

Up until 1997, no cases of termite fishing using a twig to fish for termites (Macrotermes sp.) were ever observed at Bossou, although Macrotermes mounds are common within the home range of the chimpanzees. In 1997, during the end of the rainy season, an adult female, Yo, and her juvenile offspring, Yolo, aged six at the time, were observed using a short flexible stalk of a terrestrial herbaceous plant to fish for Macrotermes termites (Humle, 1999). They would probe the tool into a hole of the mound and, on withdrawal of the tool, the chimpanzees brought the tip end to their lips to ingest the termites.

Water drinking by the Bossou chimpanzees:

The chimpanzees of Bossou also use leaves as a sponge or as a recipient for drinking water (Sugiyama, 1995; Tonooka et al, 1994; Tonooka, 2001). As well as the sponging technique, a new technique for drinking was observed at Bossou, whereby the chimpanzees would fold a leaf in their mouth and placed it into the water hole using it as a receptacle. This behavior differs from that observed at other chimpanzee field sites, where chimpanzees only use leaves as a leaf sponge for drinking water. The outdoor laboratory was also recently set up to observe this behavior in more details.

Pestle Pounding:

Pestle pounding was first observed by professor Sugiyama in 1990 (Sugiyama, 1994).
It consists of several discrete sequential behavioural components (Yamakoshi & Sugiyama, 1995):
1. A chimpanzee will climb to the centre of the crown of an oil palm tree.
2. It usually proceeds to spread out the radiating mature leaves using its hands and feet in order to expose the base of the central young shoots.
3. These young shoots are removed by tugging to gain access to the apical meristem.
4. The petiole of these spear leaves is then often eaten and chewed.
5. A palm-leaf petiole is used as a pestle or a tool (see photo) to pound at and excavate the centre of the palm crown, resulting in a softening of the palm heart.
6. The palm heart is eaten and extracted by hand.
The Bossou community of chimpanzees is currently the only community where this type of tool use has been observed.

Algae scooping:

In the summer of 1995, a new type of tool using behavior was observed and performed by individual chimpanzees of the Bossou community (Matsuzawa et al, 1996). The chimpanzees were observed using a wand to scoop floating algae (Spirogyra sp.) off the surface of ponds, a behavior which was later defined as algae scooping. At the vicinity of the ponds, large amount of stalky and fern vegetation was available. The chimpanzee selected a stalk which it broke off with its teeth. It would then fashion a fishing "rod" devoid of leaves. The tool would then be inserted into the water and a scooping action of the wrist usually followed to fish out the surface algae. The stick was then brought up to the mouth and the algae eaten.

Non-subsistence tool-use behaviors displayed by the Bossou community:

Leaf cushion:

Bossou chimpanzees were observed to arrange large leaves on the ground as cushions to sit on in order to avoid contact with the wet, moist ground beneath (Hirata et al, 1998).

Exploratory probing:

Chimpanzees at Bossou have been observed to insert sticks or twigs into tree-holes or into the ground and then sniffing the tip upon removal as a form of exploratory behavior.

Leaf clipping:

While performing this behavior, a chimpanzee picks one to several soft leaves, grasps the petiole between the thumb and the index finger and then proceeds to repeatedly remove the leaf-blade with the incisors that results in the production of a conspicuous and distinct noise.
This behavior is clearly ritualized and serves as a communicatory signal. The frequencies of mouth to finger leaf clipping vary across chimpanzee communities and leaf clipping has not been observed in all communities of chimpanzees studied thus far. For example, leaf clipping is absent from the behavioral repertoire of the chimpanzees of Gombe. However, it has been recorded at all other long-term study sites across Africa. At Bossou and Mahale (K-group), exclusive use of the mouth for leaf clipping has been observed, whereas at other long-term field sites, both techniques have been noted with varying frequencies (Whiten et al, 1999).
This behavior has a communicatory function that is usually context-dependent. Indeed, the signaling function of leaf clipping varies across communities. At Bossou, the great majority of examples of leaf clipping were done in clear frustration or in frustration-related aggression, while only a few instances took place in a courtship context (Sugiyama, 1981). During the habituation period of the Bossou chimpanzees, individuals surprised in trees would leaf clip while watching the observer. Once habituation had progressed, this form of leaf clipping was considerably reduced and is now mainly only seen in youngsters at play.

Aimed Throwing during displays or other aggressive contexts:

Chimpanzees at Bossou, as well as at many other study sites across Africa, have been observed to throw a branch at another nonspecific during display or fighting contexts or at human observers who happened to come too close!

Finally, different communities of wild chimpanzees possess different tool use repertoires. However, not all of this regional and local variation can be explained by the demands of the physical and biotic environments in which they live. Many of these behavioral variants are socially learnt and are maintained from one generation to the next. These have now been acknowledged as representing cultural behaviors (Whiten et al, 1999).

Chimpanzee Culture!

REFERENCES

If you would like to find out more about research at Bossou, please click here.

You will find a list of all the references ever published about Bossou. Enjoy!