Climate induced stress and mortality in vervet monkeys

Abstract

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.

Differential impact of severe drought on infant mortality in two sympatric neotropical primates

“…However, primate species differ in their susceptibility to these extreme events depending on behavioural, ecological, morphological and life-history traits [16]. In a wide range of natural primate populations, extremes in climatic water balance, including both severe drought and excessive rain, have been associated with elevated mortality [17][18][19][20], reduced fecundity [21][22][23], delayed birth seasons [22], declines in population density [24] and demographic perturbations [25]. Furthermore, extreme weather events can trigger periods of critically low resource availability [26].…”

“…Furthermore, extreme weather events can trigger periods of critically low resource availability [26]. For example, in vervet monkeys (Chlorocebus pygerythrus), high mortality during a severe drought was presaged by reduced food availability and an increase in physiological markers of stress [19]. In savannah baboons (Papio spp.…”

Male characteristics as predictors of genital color and display variation in vervet monkeys

“…Several factors may have influenced our results, masking a potential impact of color. First, a drought in South Africa in 2016 led to dehydration and affected the survival of our population (Young et al 2019). This could have influenced the blue color of the scrotum due to reduced tissue fluid in the dermis (Price et al 1976;reviewed in Caro 2005) and may have added to the reduced variation in vervet blue scrotal color described previously.…”

Sick and Tired: Polyparasitism, Food Stress and Sickness Behaviour in a Gregarious Mammal

“…The study area comprises semi-arid riverine woodland [28], with a declining annual average rainfall of 386 mm, and average annual minimum and maximum temperatures of 10ºC and 27ºC respectively. The region experiences periodic droughts that are severe enough to be a primary source of mortality for animals in our study groups [26].…”

“…Here, we use a comprehensive dataset comprised of detailed physiological (faecal glucocorticoid metabolites), environmental, behavioural and parasite data to assess how these factors interact to shape behavioural responses to infection in a population of a highly social, wild mammal, specifically, the vervet monkey (Chlorocebus pygerythrus), in a semi-arid region of South Africa. Previous work in this population has identified complex relationships between behaviour and environmental conditions, with food resources, temperature, rainfall, and standing water availability strongly influencing activity budgets and mortality [25,26].…”