Differences in Diet Between Six Neighbouring Groups of Vervet Monkeys

Abstract

The comparative approach provides a powerful tool to study evolutionary questions on both intra-and interspecific variation. It has been applied to a great variety of taxa, including primates. Primate studies differ from those on most other taxa in two ways: first, data from most study sites contain information about only one group. Second, primatologists have used the comparative approach also to identify local traditions, that is, behaviours that spread through social learning. Here, we evaluate the appropriateness of such data by comparing the diet composition of six neighbouring groups of vervet monkeys, Cercopithecus aethiops. We used scan samples to collect diet data, and abundance measures and phenology to assess the availability of the 14 most important tree species utilised during the study. We calculated indices of diet overlap, which were highly variable and could be remarkably low. Furthermore, we found significant differences between group diets with respect to the relative utilisation of 13 of the 14 tree species. For all 13 species, we found positive correlations between local abundance and appearance in the diet, consistent with the importance of local ecology for diet composition. Nevertheless, more detailed comparisons of pairs of groups often revealed significant mismatches between the relative importance of a tree species and its local abundance. In conclusion, local variation merits increased attention by primatologists. While our results are compatible with the possibility that traditions exist on a local (group) rather than population scale, alternative explanations have to be considered.

On the neglected behavioural variation among neighbouring primate groups

“…Tournier et al () analysed scan samples with diet data and assessed the availability of the 14 most important tree species utilized by the monkeys during the study, using abundance measures and phenology. They calculated indices of diet overlap between groups, which were highly variable and could be remarkably low.…”

“…For abbreviations of tree species, see 1. Variation in the diet of vervet monkeys (Figure in Tournier et al, )…”

“…This approach might yield a more realistic understanding of the wide range of intergroup behavioural variation, and thus the size and scope of each potentially unique repertoire of traditions. tion with the abundance of these trees in each home range (Tournier et al, 2014). 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, 2013).…”

“…Here, I review intergroup behavioural variation observed in neighbouring groups (with often overlapping home ranges) of wild vervet monkeys. 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, ).…”

Dietary Variation in Diana Monkeys (Cercopithecus diana): The Effects of Polyspecific Associations

“…In other words, local patterns of availability and tree species distribution may make it more profitable for one group to focus on, for instance, the fruit of Uapaca guinensis, while another group may focus more intensively on Diospyros soubreana during the same period. While we are aware of no evidence of Diana monkey group-level traditions, they are not precluded as possible explanations for intergroup dietary variation such as those observed in chimpanzees, Japanese macaques, capuchins, and vervet monkeys [McGrew, 1998;Hirata et al, 2001;Perry and Manson, 2003;Tournier et al, 2014].…”