Social reciprocity and interchange in long-tailed macaques (Macaca fascicularis)
Gumert, Michael David
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Social grooming is a common and potentially valuable act for long-tailed macaques. It may be traded reciprocally or interchanged with other acts such as tolerance, sexual activity, and infant handling. Social exchange related to grooming may be contingent on specific acts of grooming, and thus traded, or it may just be a by-product of social relationships and thus not traded. If grooming can be traded, biological market theory predicts that grooming may be considered as “payment” for other social acts and would vary with supply and demand of available partners. If grooming is traded directly as payment for other social acts, specific acts of grooming should facilitate reciprocation and interchange. Also, the number of available partners (i.e. supply) should negatively influence grooming duration. In the first study, I analyzed sequences following grooming bouts to test the hypothesis that reciprocation and interchange can be linked to specific acts of grooming. I found that specific acts of grooming facilitated subsequent reciprocation and interchange with tolerance or sexual activity. In the second study, I investigated exchange patterns of female-to-mother with infant grooming and its relation to the supply of infants. I found that after mothers with infants received grooming from a female, infant contact by the grooming female was facilitated. I also found a negative relationship between grooming bout duration and the number of infants per female surrounding female-to-mother grooming bouts associated with infant handling. It seemed that grooming did facilitate infant handling and that grooming duration was negatively related to infant supply. In the third study, I investigated whether there was a relationship between grooming duration and the supply of females around male-to-female grooming bouts associated with mating. I found a negative relationship between bout duration and the number of females per male surrounding a mating-related grooming. From these studies, I concluded that specific acts of grooming can facilitate reciprocation and interchange and that the supply of partners is related to the amount of grooming payment an individual will offer to their partner. Overall, some grooming exchanges appear to occur as trades, where grooming is “payment” for other social acts such as more grooming, tolerance, sexual activity/mating, and infant handling.