Ingestion of terrestrial plastic pollution by free-roaming livestock, including working donkeys: an interdisciplinary assessment

In areas where waste management is inadequate, the welfare of free-roaming animals can be significantly affected by the ingestion of plastic waste, potentially impacting human livelihoods and health. However, the effect of plastic pollution on terrestrial animals is poorly understood. Using a combination of methodologies from animal behaviour, environmental and social sciences, this study assesses the effects of plastic pollution on donkeys, cattle and their owners in Kenya. Behavioural observations suggested that donkeys and cattle preferentially fed at waste sites, where 1 in every 10–20 items ingested were plastic. Faecal sampling also showed much higher concentrations of microplastics than those reported in previous studies of farmed cattle and significantly higher concentrations in the faeces of donkeys and cattle grazing at waste sites compared to rural areas. Survey data showed that the majority of livestock owners believed that plastic pollution was a problem, and nearly a third of local residents had witnessed an animal becoming ill following plastic ingestion, reporting mortality rates of 78%. Triangulating data from multiple methods highlights the risks terrestrial plastic pollution poses to domestic animals, demonstrating the need for interdisciplinary projects that tackle this important issue by addressing the interconnectedness of human behaviour, animal welfare and environmental health.