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.

Tolerance of muzzle contact underpins the acquisition of foraging information in vervet monkeys (Chlorocebus pygerythrus).

Muzzle contact, where one animal brings its muzzle into close proximity to that of another, has often been hypothesized as a straightforward means of socially mediated food investigation. Using 2,707 observations of muzzle contact occurring across 3 troops of wild vervet monkeys (Chlorocebus pygerythrus), we tested this social learning hypothesis. We first explored the social structuring of muzzle contact by analyzing the characteristics of initiators and receivers. Similar to previous research, juveniles initiated contact at higher rates than adults, particularly toward adult females and animals with lower dominance rankings. The highest number of contacts occurred between kin compared to contacts between nonkin. However, on the whole, contacts occurred at low rates, even among kin dyads. We next determined whether muzzle contact was used as a means to learn socially, specifically by animals seeking foraging information. We found that initiators did not overwhelmingly target foragers, meaning animals do not appear to directly seek information about food during muzzle contact. However, animals that contacted foragers were more likely forage themselves in comparison to those that contacted nonforagers, suggesting that foragers do provide food information. These findings indicate that both kin and low-ranking animals serve as discriminative stimuli for social tolerance and that foraging animals serve as discriminative stimuli for food availability. We conclude that broad social tolerance, rather than the recipient's knowledge, is the most likely antecedent to muzzle contact and that animals engage in this behavior as a low-cost means of maintaining a baseline level of information about their environment. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Climate induced stress and mortality in vervet monkeys.

As the effects of global climate change become more apparent, animal species will become increasingly affected by extreme climate and its effect on the environment. There is a pressing need to understand animal physiological and behavioural responses to climatic stressors. We used the reactive scope model as a framework to investigate the influence of drought conditions on vervet monkey (Chlorocebus pygerythrus) behaviour, physiological stress and survival across 2.5 years in South Africa. Data were collected on climatic, environmental and behavioural variables and physiological stress via faecal glucocorticoid metabolites (fGCMs). There was a meaningful interaction between water availability and resource abundance: when food availability was high but standing water was unavailable, fGCM concentrations were higher compared to when food was abundant and water was available. Vervet monkeys adapted their behaviour during a drought period by spending a greater proportion of time resting at the expense of feeding, moving and social behaviour. As food availability decreased, vervet mortality increased. Peak mortality occurred when food availability was at its lowest and there was no standing water. A survival analysis revealed that higher fGCM concentrations were associated with an increased probability of mortality. Our results suggest that with continued climate change, the increasing prevalence of drought will negatively affect vervet abundance and distribution in our population. Our study contributes to knowledge of the limits and scope of behavioural and physiological plasticity among vervet monkeys in the face of rapid environmental change.