Microplastic contamination in terrestrial ecosystems: A study using barn owl (Tyto alba) pellets

Microplastics (MPs) are recognised as an emerging environmental problem that needs to be carefully monitored. So far, MPs have been widely recorded in marine and freshwater ecosystems. Still, few studies have focused on MP occurrence in terrestrial ecosystems, although soils are suspected to be one of the main MP reservoirs. To test a non-invasive method for assessing MP contamination in terrestrial ecosystems, we analysed the pellets of a top terrestrial predator, the barn owl (Tyto alba). Sixty pellets were collected from three agricultural areas (20 pellets each) and analysed to assess both barn owl diet and MP content. Thirty four MPs were confirmed by micro-Fourier Transform Infrared Spectroscopy (μ-FTIR) analysis in 33% of the pellets (min-max 1 – 5 MPs per pellet). Most of the detected items were microfibres (88.2%). Polyethylene terephthalate, polyacrylonitrile and polyamide were the most abundant polymers. One of the three sites was significantly less contaminated. In the two sites with the highest MP occurrences, barn owl diet was characterised by predation on synanthropic rodents, particularly brown rats (Rattus norvegicus), which may indicate habitat degradation and increased exposure to MPs. Analyses also suggest that Savi's pine vole (Microtus savii) is the prey least at risk of MP contamination, probably due to its strictly herbivorous diet. We argue that the analysis of barn owl pellets may represent a cost-effective method for monitoring MP contamination in terrestrial ecosystems.