The impact of microplastic contamination in cow manure on reproductive behavior and larval survival in the dung beetle Onthophagus taurus

Abstract

Microplastics are an emerging environmental hazard on a global scale. Their detection in agricultural environments is of particular concern not only for food contamination, but also because microplastics negatively impact detritivores and their ecosystem functioning. Dung beetles in particular provide vital ecosystem services in agricultural environments and are often vulnerable to anthropogenic hazards, but whether they are affected by microplastics remains unclear. Here, we test whether artificial contamination of cow dung with thermoplastic polyurethane (TPU) has the potential to affect the juvenile development and maternal behavior of the bull-headed dung beetle Onthophagus taurus. Dung beetles exhibited high mortality when exposed to elevated concentrations of TPU. In addition, females were equally likely to provision offspring with TPU-spiked (and lethal) cow dung as with control dung, suggesting that females cannot differentiate between highly toxic microplastic-contaminated and uncontaminated cow dung. Our findings highlight potentially severe consequences for dung beetles if microplastics persist and accumulate, although the levels of exposure in the field are unknown. Although the direct environmental hazards and the mechanisms mediating the negative impacts of TPU microplastics remain to be assessed, this study suggests that microplastics may negatively impact dung beetles and their ecosystem services. Future work assessing exposure levels in the field as well as dung beetles potential to evolve resistance against microplastic pollution will be necessary to assess the long-term impact of microplastic presence on dung beetle ecosystem functioning.