[Excerpt] Tactical Deception in Chimpanzees

Part Of: Politics sequence
Excerpt From: de Waal (1982). Chimpanzee Politics
Content Summary: 1400 words, 7 min read

Example 1

On a hot day two mothers, Jimmie and Tepel, are sitting in the shadow of an oak tree while their two children play in the sand at their feet (playfaces, wrestling, throwing sand). Between the two mothers the oldest female, Mama, lies asleep. Suddenly the children start screaming, hitting, and pulling each other’s hair. Jimmie admonishes them with a soft, threatening grunt, and Tepel anxiously shifts her position. The children go on quarreling, and eventually Tepel wakes Mama by poking her in the ribs several times. As Mama gets up Tepel points to the two quarreling children. As soon as Mama takes one threatening step forward, waves her arm in the air, and barks loudly the children stop quarreling. Mama then lies down again and continues her siesta.

INTERPRETATION. In order to understand this interpretation fully, it is important to know two things: first, that Mama is the highest-ranking female and is greatly respected; and second, that conflicts between children regularly engender such tension between their mothers that they too come to blows. This tension is probably caused by the fact that each mother wishes to help her own child and to prevent the other from interfering in the quarrel. In the case of the example above, when the children’s game turned to fighting, both mothers found themselves in a painful situation. Tepel solved the problem by activating a dominant third party, Mama, and pointing out the problem. Mama obviously realized at a glance that she was expected to act as arbitrator.

Example 2

Yeroen hurts his hand during a fight with Nikkie. Although it is not a deep wound, we originally think that it is troubling him quite a bit, because he is limping. The next day a student, Dirk Fokkema, reports that in his opinion Yeroen limps only when Nikkie is in the vicinity. I know Dirk as a keen observer, but this time I find it hard to believe him. We go to watch, and it turns out that he is indeed right: Yeroen walks past the sitting Nikkie from a point in front of him to a point behind him and the whole time Yeroen is in Nikkie’s field of vision he hobbles pitifully, but once he has passed Nikkie his behavior changes and he walks normally again. For nearly a week Yeroen’s movement is affected in this way whenever he knows Nikkie can see him. 

INTERPRETATION. Yeroen was playacting. He wanted to make Nikkie believe that he had been badly hurt in their fight. The fact that Yeroen acted in an exaggeratedly pitiful way only when he was in Nikkie’s field of vision suggests that he knew that his signals would only have an effect if they were seen; Yeroen kept an eye on Nikkie to see whether he was being watched. He may have learned from incidents in the past in which he had been seriously wounded that his rival was less hard on him during periods when he was (of necessity) limping.

Example 3

Wouter, a young male chimpanzee of almost three, gets into a quarrel with Amber and screams at the top of his voice. At the same time he advances aggressively towards Amber. His mother, Tepel, goes over to him and quickly places her hand over her son’s mouth, smothering his screams. Wouter calms down and the quarrel is over. 

INTERPRETATION. Noisy conflicts attract attention. If they last too long, one of the adult males will come over and put an end to them. When a bluffing male approaches, Wouter will automatically seek refuge near his mother. This means that she runs the risk of receiving the punishment meant for her son. Tepel wanted to avoid this risk by shutting up Wouter before things went too far. 

This is not the only known instance of enforced silence. I have also seen a mother place a finger over the small mouth of her baby when the latter started barking aggressively at a dominant group member from the safety of her lap. Once again this was probably due to the mother’s reluctance to get drawn into difficulties because of a social faux pas committed by her child.

Example 4

Dandy is the youngest and lowest ranking of the four grown males. The other three, and in particular the alpha male, do not tolerate any sexual intercourse between Dandy and the adult females. Nevertheless every now and again he does succeed in mating with them, after having made a “date.” When this happens the female and Dandy pretend to be walking in the same direction by chance, and if all goes well they meet behind a few tree trunks. These “dates” take place after the exchange of a few glances and in some cases a brief nudge.

This kind of furtive mating is frequently associated with signal suppression and concealment… On one occasion Luit was making advances to a female while Nikkie, the alpha male, was lying in the grass about 50 meters away. When Nikkie looked up and got to his feet, Luit slowly shifted a few paces away from the female and sat down, once again with his back to Nikkie. Nikkie slowly moved towards Luit, picking up a heavy stone on his way. His hair was standing slightly on end. Now and then Luit looked round to watch Nikkie’s progress and then he looked back at his own penis, which was gradually losing its erection. Only when his penis was no longer visible did Luit turn around and walk towards Nikkie. He briefly sniffed at the stone Nikkie was holding, then he wandered off leaving Nikkie with the female…

INTERPRETATION. In all these examples sexual signals are either concealed or suppressed… The males are faced with the problem that the evidence of their sexual arousal cannot disappear on command, but they too have their solutions. The audacity of Luit actually sniffing at the weapon Nikkie held in his hand only goes to show how sure he was that the alpha male would find no cause to proceed against him. 

This behavior is in marked contrast to an incident I once witnessed between two male macaques. The alpha male met another male several minutes after the latter had secretly mated, Alpha could not possibly have known anything about this, but the other male acted unnecessarily timidly and submissively. His behavior was so exaggerated that, If the alpha male had had a chimpanzee’s social awareness, he would certainly have realized what the matter was. Luit’s behavior after his abortive adventure was very different. There was no trace of a “guilty conscience.” Chimpanzees are masters of pretense and will seldom put an idea into the head of the unsuspecting.

Social Intelligence Hypothesis

Once we have witnessed a number of striking instances of social manipulation and recognized that chimpanzees are more than highly Intelligent, we are forced to consider the nature of the extra faculty they have which most other species appear to lack: the ability to think purposefully. Some goal-directed behavior occurs among chimpanzees, however, without there being any past proof of the effectiveness of the result. They seem to be able to devise effective, on-the-spot solutions, such as in example 1, when Tepel woke Mama and pointed to the two quarreling children, or in example 3, where she effectively silenced her son. 

The ability to combine past experiences in order to achieve a goal is best described as reasoning and thought; no better words exist. Instead of testing a particular course of action through actual trial and error, chimpanzees are able to weigh the consequences of a choice in their heads. The result is rational behavior. Primates take such a mass of social information into account, and are so finely attuned to the moods and intentions of others, that it has been speculated that their high intelligence evolved in order to deal with an increasingly complex group life. This idea, known as the social intelligence hypothesis, may also apply to the enormous brain expansion in our own lineage.

Addendum

These examples, and dozens of others from other primate species, were collated in Whiten & Bryne (1988). They distinguish between forms of deception, including concealment, distraction, image projection etc.

  • Whiten & Byrne (1988). Tactical deception in primates

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