Negotiations over Grooming in Wild Vervet Monkeys (Chlorocebus pygerythrus)

Abstract

Mutual grooming plays a central role in the establishment and maintenance of social relationships in primates. Allogrooming has two main functions: hygiene and bonding with partners. The duration of grooming bouts is commonly used in studies of the functional aspects of grooming, but few reflect on the proximate mechanisms that determine grooming bout lengths. As it is highly unlikely that groomer and groomee prefer exactly the same bout length, we are likely to observe the result of some form of negotiation. We currently lack information about the signals that primates employ to inform others about their intentions and desires concerning grooming interactions. From October 2006 until April 2007 we studied three behaviors shown in grooming interactions that could potentially have a signaling function in the negotiation process over the initiation and length of grooming bouts among adult females of two vervet groups freely ranging in the Loskop Dam Nature Reserve, South Africa: approaching another individual as far as that resulted in a grooming session, changing of the body position by the groomed individual, and lip smacking. We found that "approach" did not reliably predict which individual would receive grooming first, although approaching individuals groomed significantly more than those approached. Thus, in Erica van de Waal and Martina Spinelli are joined first authorship.

On the neglected behavioural variation among neighbouring primate groups

“…The reason for intergroup variation in this signal, observed in the context of an adult female grooming another with her mouth, remains unclear. The authors explain lip smacking as a request for tolerance when directed to a higher‐ranked individual, or as an appeasement signal when directed to a lower‐ranked individual (van de Waal, Spinelli, et al, ), but this did not explain the variation found between the two study groups. Though the explanation remains unclear, I suggest deeper consideration of this group‐level variation.…”

“…Mean lip smacks per second performed by groomers during grooming‐with‐mouth events in relation to the recipient’s rank. The dashed lines represent the linear trend lines (Figure 7 in van de Waal, Spinelli, et al, )…”

“…This data set was already published by van de Waal, Spinelli, et al (). To summarize their methods, lip smacking data were extracted from ad libitum video recordings of grooming bouts between adult females of two study groups.…”

“…The term “rank” referred to the place of an individual in the dominance hierarchy of adult females with rank 1 being that of the highest ranking female. The goal was to study communicative signals (body presentations and lip smacking) produced during grooming between adult females of two groups of vervet monkeys (van de Waal, Spinelli, et al, ).…”

“…First, I report intergroup dietary variation found through analyses of the amount of foraging on 14 preferred fruiting tree species, in association with the abundance of these trees in each home range (Tournier et al, ). Second, I report results on intergroup variation in the frequency of lip smacking (a facial expression) during grooming between dyads of adult females (van de Waal, Spinelli, Bshary, & Noë, ). Third, I describe intergroup variation in social network structure and dynamics (Borgeaud, Sosa, Sueur, Bshary, & Waal, ).…”