Researchers found traces of plastic in the faeces of small mammals in England and Wales in more than half of all species examined, according to a study published in the journal Science of the Total Environment. The authors from the University of Exeter, the Mammal Society, and the University of Sussex reported that the amount of plastic in these animals was similar to what is found in human studies.
“Much is known about the impact of plastic on aquatic ecosystems, but very little is known about the same with terrestrial systems,” said Fiona Mathews, Professor of Environmental Biology at the University of Sussex. “By analysing the droppings of some of our most widespread small mammals, we’ve been able to provide a glimpse of the potential impact plastic is having on our wildlife – and the most commonly found plastics leaking into our environment.”
In the study, researchers found plastic polymers in four out of seven species they analysed: the European hedgehog, wood mouse, field vole, and brown rat were all positive. The authors were expecting to see higher plastic concentrations in samples from urban species and lower levels in herbivorous species, but it turned out that ingestion of plastic can occur across locations and affects animals with different dietary habits, including herbivores, insectivores and omnivores.
“It’s very worrying that the traces of plastic were so widely distributed across locations and species of different dietary habits. This suggests that plastics could be seeping into all areas of our environment in different ways,” said Emily Thrift, a graduate of the University of Sussex. “We’re also concerned that the European hedgehog and field vole are both species suffering declines in numbers in the UK.”
The team analysed 261 faecal samples and found that 16% of them contained plastic. The most common type was polyester, polyethylene (used in single-use packaging), and polynorbornene (used in the rubber industry). Polyester represented almost a third of al fragments found and was found in all species except the wood mouse. The authors suggested that these microfibres can easily enter the wastewater system via household washing and eventually end up on the land if sewage sludge is used as a fertiliser.
“In the UK, plastic pollution can often seem like a problem somewhere else when most images are of polluted shorelines of tropical landscapes or charismatic organisms like turtles or sea lions. This study brings the focus home, into our lands and in some of our much beloved mammal species. Further, it demonstrates that the amount of plastic waste we produce is having an impact,” said Dr. Adam Porter from the University of Exeter. “We must change our relationship with plastic altogether; moving away from disposable items and moving towards replacing plastic for better alternatives and establishing truly circular economies.”
Over a quarter of the plastics found were biodegradable. These plastics may degrade faster than polymers, but they can still stay in the environment for some time and be ingested by small animals. The authors defend that further research is vital to understanding the long-term impact of these plastics.
For the team, these plastics entered the species’ digestive system as a result of being eaten directly or via the consumption of contaminated prey. It’s easy for these animals to mistake plastic for food or use these materials as nesting material. Based on these results, the authors are also concerned about the impact of plastics on the food chain.
“In our study, droppings from European hedgehogs carried the highest quantity of plastic polymers. As a species, they are already in decline in the UK for reasons that are largely unknown, and they are classified as Vulnerable to Extinction on the IUCN-compliant regional Red List,” added Prof. Mathews. “European hedgehogs consume earthworms, and previous studies have found these to contain microplastics. So we really need further research to establish the scale and route of exposure more precisely, and to assess prevalence in predatory species that consume small mammals, so that we can take adequate steps to try to protect our declining wildlife from plastics.”
Thrift E, Porter A, Galloway T, Coomber F, Mathews F (2022) Ingestion of plastics by terrestrial small mammals. Science of the total environment, https://doi.org/10.1016/j.scitotenv.2022.156679