Group Responses To Specially Skilled Individuals in a Macaca Fascicularis Group
Author: Stammbach, Eduard
Source: Behaviour, Volume 107, Numbers 3-4, 1988 , pp. 241-266(26)
Abstract:The aim of this study was to investigate the capability of monkeys to assess special characteristics in conspecifics. In a first phase I ascertained that all members of a colony of longtailed macaques (Macaca fascicularis) were able to attain food by manipulating a one lever apparatus, thus introducing the "tradition" of lever pulling. Then, experiments were carried out on subgroups of the colony where only one of the lower ranking subgroup members was trained to succeed in a more complex task where three levers had to be pulled in a correct sequence. Eight specialists were established in sequence. These specialists became food producers for themselves and for the other group members. Each trial of a specialist's series was carried out in two phases. In the first, the food phase, the food dispensing apparatus was active and responses of other subgroup members to the food producing specialist were observed. In the second, the social phase, the apparatus remained inactive and observations focused on social interactions of the subgroup. As expected, primarily high ranking subgroup members attempted to participate in the food rewards gained by the specialist. It is shown that high ranking animals began to hold back their initial chasing of the specialist from the food site in course of the trials and were soon tolerated to sit near the subordinate food producer. Furthermore, some of the non-specialists began to follow or even to pass the specialist when he was approaching the apparatus to manipulate the levers. These non-specialists thus indicated that they were able to anticipate later actions. In seven out of 55 specialist-non-specialist relationships all predicted changes in social interactions occurred. In the majority of the dyads in which a change in social affiliation was registered an increase of grooming or spatial proximity was positively correlated with the amount of benefit gained from the specialist. In the social phase of the trials the non-specialists gave more grooming to the food producers and maintained spatial proximity even in this second phase. To conclude: At least some of the group members became aware of the skills of the specialists and adapted their behaviour accordingly as if to maximize benefits from their skills. Previous studies had already suggested that monkeys know about social position, social relationships and kinship of group members. This study adds a new aspect of knowledge, namely knowledge on capabilities and skills of others. Differential knowledge allows monkeys to select partners optimally according to their skills and social position.
Document Type: Research article
Publication date: 1988-01-01