A Statistical Analysis of the Social Behavior of the Male Stumptail Macaque(Macaca arctoides)
Results Page 7

Title/summary page


Page 1


Materials and Methods
Pages 2 - 3


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Figures 1- 8
Figures 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8


Tables I-IV
Tables I - II - III - IV

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Between-Animal Sequences

Most of the 40 significant between-animal sequences of acts and postures that occurred more than twice in the study may be understood as causal interactions between the two monkeys. All significant sequences are listed in Table IV. Offense by a dominant caused defense in dominants or submission in subordinates, as illustrated by flowcharts in Figure 6; this accounts for 17 significantly nonrandom sequences. Running towards and mounting by one dominant caused presenting and autostimulation in a second dominant, as shown in Figure 7. Sexual interactions between dominants and subordinates also followed a few stereotyped sequences as illustrated in Figure 8. Ten significantly nonrandom dyads are illustrated in these figures of sexual behavior. The flowcharts accurately reflect triadic as well as dyadic data, as may be seen from the obtained/expected frequency ratios for triads as well as those for dyads displayed in the figures.

In aggressive interactions between dominant and subordinate, as shown in Figure 6, the attack of the former was relatively stereotyped, while the submission of the latter was more variable, consisting of crouching or standing or sitting or running away. The dominant did not vocalize or make facial expressions, while the subordinate's reaction included screaming, pant-grunting, open mouth threat, bared-teeth face, and grinning. Note that hitting by the dominant and hitting out without contact by the subordinate tended to occur at that point in a sequence when the opponent stood still, and that they tended to terminate the aggressive interaction.

Aggressive interactions between two dominant monkeys often began with the same kind of biting-the-back that occurred against subordinates, but they were then transformed by frontal biting into a defensive encounter instead. As illustrated in Figure 3, the two monkeys engaged in alternating rough restraint and biting the face as they stood upright facing and gripping each other. These were the most damaging fights in the study. They were carried on in remarkable silence, punctuated only by the labored breathing of the two struggling monkeys and the sounds of body and teeth contact during biting. The only facial expressions were alternate biting and grimacing, the latter reflecting perhaps the high degree of exertion or pain.

Sexual interactions between two dominants were all variations on a single pattern as illustrated in Figure 7. One dominant ran towards the second, who presented, and the first then mounted. The mounting and presenting could be either brief or prolonged before the animals proceeded to masturbation or autostimulation. Only the animal who initially mounted engaged in true masturbation to orgasm; the one who had been mounted engaged in autostimulation without orgasm. Various facial expressions and vocalizations accompanied the mounting, presenting, and autostimulation, but did not accompany the prolonged masturbation that followed the mounting.

Sexual interactions between a dominant and a subordinate differed as a function of which monkey mounted the other as illustrated in Figure 8. Mounting by the subordinate was prolonged, and the resulting sequence was similar to that between two dominants. Mounting by the dominant was brief; unlike the other types of sexual interactions it was often preceded by masturbation by the subordinate and followed by the dominant's manipulation of the genitals of the opponent. Unlike the case of interactions between two dominants, all of the sexual behaviors, including masturbation, were accompanied by characteristic vocalizations and facial expressions.

"Following" behavior accounted for a number of nonrandom dyads of behavior sequences between monkeys. Walking away by one monkey led to walking towards by the second. Similarly, running away by one monkey led to running towards by the second. In each case, the sequence was more likely to occur when it was initiated by the dominant monkey. Another pair of highly significant behavior sequences may have been related: climbing up by one monkey led to climbing up by the second; and climbing down by one led to climbing down by the other. Again, the sequences were more likely to occur when initiated by the dominant. Two other between-animal sequences might be considered as special cases of following; both monkeys tended to engage in patrol locomotion or parallel locomotion at the same time.

Allogrooming interactions were also significant when they were initiated by the dominant who presented or lay down and was subsequently groomed by the subordinate.

There were significant vocal interactions as well as interactions of acts and postures; these consisted of vocal imitation. Each monkey imitated the grunting, pant-grunting, and tremulo exhalations of the other regardless of their relative dominance status. A series of grunts were often echoed back and forth by the two monkeys three or four times in rapid succession in obvious response to each other.

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