What you have, not who you know: food-enhanced social capital and changes in social behavioural relationships in a non-human primate.

Social network position in non-human primates has far-reaching fitness consequences. Critically, social networks are both heterogeneous and dynamic, meaning an individual's current network position is likely to change due to both intrinsic and extrinsic factors. However, our understanding of the drivers of changes in social network position is largely confined to opportunistic studies. Experimental research on the consequences of in situ, controlled network perturbations is limited. Here we conducted a food-based experiment in rhesus macaques to assess whether allowing an individual the ability to provide high-quality food to her group changed her social behavioural relationships. We considered both her social network position across five behavioural networks, as well as her dominance and kin interactions. We found that gaining control over a preferential food resource had far-reaching social consequences. There was an increase in both submission and aggression centrality and changes in the socio-demographic characteristics of her agonistic interaction partners. Further, we found that her grooming balance shifted in her favour as she received more grooming than she gave. Together, these results provide a novel, preliminary insight into how in situ, experimental manipulations can modify social network position and point to broader network-level shifts in both social capital and social power.

Estimates of life history parameters in a high latitude, arid-country vervet monkey population.

We present data on life history parameters from a long-term study of vervet monkeys in the Eastern Cape, South Africa. Estimates are presented of age at first conception for females and age at natal dispersal for males, along with the probability of survival to adulthood for infants born during the study, female reproductive life-span, reproductive output (including lifetime reproductive success for a subset of females), and inter-birth interval (IBI) duration. We also assess the effect of maternal age and infant survival on length of IBI. We then go on to compare life history parameters for our population with those from two East African populations in Kenya (Amboseli and Laikipia). We find there is broad consensus across the three populations, although mean infant survival was considerably lower for the two East African sites. Such comparisons must be made cautiously, however, as local ecology across the duration of the studies obviously has an impact on the estimates obtained. With this caveat in place, we consider that the concordance between values is sufficient to enable the values reported here to be used in comparative studies of primate life history, although data from habitats with higher rainfall and lower levels of seasonality are needed, and the results presented here should not be seen as canonical.

Causal analysis as a bridge between qualitative and quantitative research.

Yarkoni argues that one solution is to abandon quantitative methods for qualitative ones. While we agree that qualitative methods are undervalued, we argue that both are necessary for thoroughgoing psychological research, complementing one another through the use of causal analysis. We illustrate how directed acyclic graphs can bridge qualitative and quantitative methods, thereby fostering understanding between different psychological methodologies.

Gastrointestinal Parasites of Vervet Monkeys (Chlorocebus pygerythrus) in a High Latitude, Semi-Arid Region of South Africa.

Given a changing climate and large-scale human migration, understanding infectious diseases in wildlife and the factors that drive the spread of these diseases is becoming increasingly important. Owing to the close phylogenetic relationship between nonhuman primates and humans, primate parasites are of particular interest due to the potential for zoonotic disease transmission and for the study of social transmission within gregarious social groups. There is a wide range of social and environmental factors that influence the prevalence and transmission of pathogens, and identifying these, and their effects, is crucial to understanding the population-level consequences of climate change for animals that live in obligate social groups. Here we investigated gastrointestinal parasite species richness and used fecal egg counts to estimate worm intensities in 3 vervet monkey troops (Chlorocebus pygerythrus) in a high latitude, semi-arid region of South Africa. This region is characterized by unpredictable rainfall and temperature extremes in summer and winter. We identified the gastrointestinal parasites in the population and explored potential demographic predictors, namely sex and troop membership, of parasite species richness and estimated intensity. Additionally, we assessed whether there was short-term intra-individual, inter-sample consistency in egg counts. Six species of gastrointestinal helminths were identified from 3 study troops, with egg counts ranging from 0 eggs/g to 1,100 eggs/g. Neither age nor sex predicted species richness or estimated intensity. This population had the highest prevalence of parasites with an insect vector compared with all other vervet populations studied, and distinctively high prevalences of Trichostrongylus sp. (71%) and Ternidens sp. (27%). Additionally, we found intra-individual egg count consistency in the short term (mean: 32 days).