Molecular assessment of dietary variation in neighbouring primate groups

Abstract

Facing rapid environmental changes and anthropogenic habitat destruction, animal behavioural plasticity becomes an adaptive potential that needs to be considered in conservation strategies along with, for example, genetic diversity. Here, we evaluate to what extent non‐invasive environmental DNA (eDNA) methods may contribute to the assessment of intraspecies behavioural plasticity in terms of foraging behaviour. We analysed DNA metabarcoding data for plant components in the diet of four neighbouring groups of wild vervet monkeys Chlorocebus pygerythrus to identify intergroup variation (IGV). The faecal samples considered for the analyses were limited to the summer season to minimise the impact of seasonality. Each sample was attributed by observation to individuals with known life history data. A plant survey was conducted in each group home range during the study period to account for environmental variation. We observed mixed results when testing whether IGV in plant consumption was greater than intragroup variation, indicating that the influence of social dynamics must be considered. Intragroup variation was positively correlated with group size. We observed IGV in diet composition among all groups as well as in some pairwise comparisons. We found significant dietary differences between two group pairs when considering only adult females. Lastly, we observed IGV in foraging of specific plants that were not explained by their distribution, suggesting behavioural differences in selectivity between groups. Our study system and organism, being a highly social and non‐threatened primate species, with constant gene flow and overlapping territories between groups, provides an ideal model to evaluate the usage of eDNA‐based methods to better understand the impact of social factors on IGV. Our results highlight the need to consider social and demographic factors, the impact of which remains complicated to disentangle from environmental factors. However, we emphasise the great potential for studying social groups using eDNA and that such studies are needed to better understand intraspecific behavioural plasticity in wild populations.

Striking pay dirt: Contemporary methods for studying animal sociality in the wild

“…Firstly, it can be used to analyse with ever increasing precision the products of field research. Schneider et al (2023) highlight how environmental DNA can be meaningfully used to test for the presence of intergroup variation in diet in neighbouring vervet monkey groups Chlorocebus pygerythrus . While their results do not allow them to make firm conclusions regarding this question in their study groups, they provide the tools to do so across species.…”