Spatial constraints and seasonal conditions but not poaching pressure are linked with elevated faecal glucocorticoid metabolite concentrations in white rhino

Abstract

Context Due to considerable declines in African wildlife populations, most large African mammals are managed inside protected areas. Protected areas come in various sizes, and have different environmental features, climates and management strategies (i.e. ‘hands-on’ or ‘hands-off’) that can influence an animals’ homeostasis. White rhinos (Ceratotherium simum simum) are found almost exclusively within protected areas where population sizes are driven by natural factors and poaching pressures. Aims Our aim was to understand the effect of natural and anthropogenic factors on the adrenocortical response of white rhinos within three protected areas. Specifically, we wanted to understand how poaching pressure, protected area size (<500 km2), season (wet and dry) and rainfall patterns were responsible for driving adrenocortical activity in white rhino. Methods To understand the relationship between rhino adrenocortical responses and different environmental and anthropogenic stressors, we quantified glucocorticoid metabolites in faecal samples (fGCM) collected from four populations within three protected areas (i.e. two small parks, one big park) during the wet and dry seasons. Key results We found differences in seasonal fGCM concentrations, with a 42% increase during the dry season, and no differences in fGCM concentrations between the high and low poaching areas. Additionally, we found fGCM concentrations in samples from the small parks were respectively 38% and 42% higher than in samples from the large park during both the dry and wet seasons compared. Conclusions Our results suggest that white rhinos may experience physiological stress in smaller parks, especially during the dry season when resources are limited. Implications By mitigating stress associated with reduced access to resources and spatial constraints, managers may better promote the viability of large mammals in small protected areas.