Diet and traffic: anthropogenic factors that influence stress-related hormone levels in African clawless otters

Abstract

Environmental and anthropogenic factors significantly drive adrenocortical activity of animals, affecting their behaviour, distribution and survival. Understanding how animals respond to such drivers is essential for effective conservation. Spraint samples from free-ranging African clawless otters (Aonyx capensis) and camera trap data were collected from study sites categorized as natural or artificially transformed based on differences in anthropogenic disturbance levels. To determine if there were significant differences in faecal glucocorticoid metabolite (fGCM) concentrations between the Natural (Kalkfontein Nature Reserve) and Transformed (Millstream Farm) sites, we ran a linear model that included sex, season, habitat type and their interaction. fGCM concentrations differed significantly between the sexes (df=1; F 1,106=11.180; P=0.001); with males (n=32; 0.608±0.367 μg/g DW) having significantly higher fGCM concentrations compared to females (n=79; 0.414±0.399 μg/g DW, P=0.006). The fGCM concentrations differed significantly between seasons (df=1; F 1,106=45.268; P<0.001), with those in the dry winter season significantly higher (n=66; 0.631±0.420 μg/g DW), compared to the wet summer season (n=45; 0.234±0.199 μg/g DW). The fGCM concentrations differed significantly between habitat type (df=1; F 1,106=6.026; P=0.016) with fGCM concentrations of individuals from the KNR natural site (n=34; 0.285±0.199 μg/g DW) being significantly lower compared to those measured in individuals at the MF transformed site (n=77; 0.552±0.436 μg/g DW). Finally, the difference in fGCM concentrations between locations however were not dependent on season (df=1; F 1,106=0.369; P=0.544). Anthropogenic disturbance and alterations to the natural and varied prey-base of African clawless otters in an anthropogenically transformed site significantly affect their adrenocortical activity. Future research should focus on how these animals respond to anthropogenic disturbance, and what effects disturbance has on their behaviour, distribution and fitness. Mitigating human–otter conflict requires incorporating such behavioural responses into management strategies.