Raging elephants: effects of human disturbance on physiological stress and reproductive potential in wild Asian elephants.

Ruchun Tang,Wenwen Li,Xianming Guo,Li Zhang,Xiaotong Shang,Di Zhu,Andrea Fuller

doi:10.1093/conphys/coz106

Abstract

Human disturbance has become a widespread threat to wildlife viability. The Asian elephant (Elephas maximus), an endangered and disturbance-prone species, is under severe threat from habitat loss and fragmentation, human-elephant conflict and poaching. Establishing connections between human disturbance, stress responses and reproduction is crucial for assessing the long-term survivability of a species and will provide critical information for conservation management. The current study investigated the effects of human disturbance on population-level stress responses and stress-related effects on reproductive potential of wild Asian elephants in Xishuangbanna Dai Autonomous Prefecture, China. We used a radioimmunoassay to measure the concentration of fecal cortisol and estradiol in 257 samples collected from five local populations at 15 sites over 4years. Human disturbance in Xishuangbanna was quantified based on the Ecological-Niche Factor Analysis model. We found that fecal cortisol concentrations were strongly positively correlated with the degree of human disturbance and increased markedly with the expansion of tea plantations. Percentage of non-stressed individuals in a population was higher depending on the extend of undisturbed area in their home ranges. Fecal estradiol concentrations decreased significantly with increasing stress levels. Our results suggest that human disturbance poses environmental challenges to wild Asian elephant populations, and chronic exposure to human disturbance could lead to population decline. The study demonstrates the efficacy of non-invasive endocrine monitoring for further informing management decisions and developing conservation strategies.

Highlights

Human disturbance, one of the principle issues of concern in conservation, has generally been considered a widespread environmental challenge and a principle threat to biodiversity (Foley et al, 2005; Murphy and Romanuk, 2014)
We investigated the links between the degree of human disturbance, cortisol concentrations and estradiol concentrations
We tested whether the degree of human disturbance affects physiological stress and reproductive potential in wild Asian elephant populations living in Xishuangbanna, China

Summary

Introduction

One of the principle issues of concern in conservation, has generally been considered a widespread environmental challenge and a principle threat to biodiversity (Foley et al, 2005; Murphy and Romanuk, 2014). Expanding pastures, plantations and urban areas have encroached on a large portion of the natural habitats of wildlife. Animals adjust their distribution and behaviour to avoid contact with humans (Gill, 2007; Gaynor et al, 2018). As the human footprint expands, fewer areas are available for animals to seek spatial refuge from people (Venter et al, 2016). Animals in the wild must compete with humans for space and resources (Madden, 2004), which results in severe human–wildlife conflicts, and neither side benefits from such conflict

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