No evidence that grooming is exchanged for coalitionary support in the short- or long-term via direct or generalized reciprocity in unrelated rhesus macaques

Reciprocity is a prominent explanation for cooperation between non-kin. Studies seeking to demonstrate reciprocity often focus on direct reciprocity in the timescale of minutes to hours, whereas alternative mechanisms like generalised reciprocity and the possibility of reciprocation over longer timescales of months and years are less often explored. Using a playback experiment, we tested for evidence of direct and generalised reciprocity, across short and longer timescales. We examined the exchange of grooming for coalitionary support between female rhesus macaques in a population with a complete genetic pedigree. Females that received grooming were not more responsive to calls for coalitionary support from female groupmates compared to control females that received agonism or no interaction – even when the call belonged to a females’ most recent grooming partner. Similarly, females were not more responsive to calls for support from their most frequent grooming partner of the last two y...