Uncovering variation in social tolerance among wild vervet monkeys through a novel co-feeding paradigm

Social tolerance, defined as the probability of individuals maintaining proximity with minimal aggression, is essential for the functioning of social groups. This study investigates social tolerance in wild vervet monkeys ( Chlorocebus pygerythrus ), with a focus on co-feeding tolerance. Previous research has highlighted that social tolerance varies both between and within species, influenced by stable group-specific and temporally variable factors. However, it remains unclear how these differences manifest in wild primates, particularly among vervet monkeys. To address this, we employed a novel experimental co-feeding paradigm adapted for field conditions, presenting a fake grass carpet with a fixed density of corn and a plot area proportional to group size to measure group-level co-feeding tolerance. The study was conducted with two habituated groups of wild vervet monkeys at the iNkawu Vervet Project in South Africa. Results revealed significant group differences in co-feeding tolerance despite similarities in the groups’ demographics and environments. The presence of mothers with infants was associated with higher levels of co-feeding tolerance, though this effect differed by group. These findings highlight the need for further research to elucidate the factors driving group-specific social tolerance levels and the mechanisms behind these differences.