Plastic ingestion by greater one-horned rhinos in Nepal: An emerging conservation threat

Abstract

Plastic pollution is potentially a major threat to the health of terrestrial organisms, including megafauna, but its effects are relatively understudied compared to marine ecosystems. Here we document the presence of plastic macro-particles in the dung of the greater one-horned rhino (Rhinoceros unicornis) in the Terai landscape of Nepal. Field data were collected deep within Chitwan National Park and its fringe zone during the monsoon and post-monsoon season of 2020, 2021 and 2022. Over three years, we recorded plastic in ∼10% of 258 rhino dungs piles. This is an underestimate since we did not record micro-particles or search entire dungs. More dungs located deep within the national park (core zone) contained plastic compared to the fringe zone and we recorded no difference in plastic incidence between riverine forest and floodplain grasslands. Rhinos do not appear to target garbage dumps as food sources but are exposed to plastic when foraging. The plastic is carried down river during monsoonal floods and deposited in rhino habitat as the flood waters recede. The relatively higher rate of plastic detection in rhino dungs from the core zone is probably due to details of rhino ranging, and is a potential threat to other wildlife in the river floodplains. We recommend more detailed studies on the patterns and effects of plastic ingestion by rhinos and other wildlife. A comprehensive waste management system within the landscape is required to reduce such threats.