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, fGCMs 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 fGCMs 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.