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

Microplastics are an emerging environmental hazard on a global scale. Their detection in agricultural environments is of particular concern because microplastics may negatively impact insect detritivores and their ecosystem functioning. Dung beetles are important detritivores and are often vulnerable to anthropogenic hazards. Here, we test whether artificial contamination of cow dung with thermoplastic polyurethane (TPU) microplastics affects juvenile development and maternal behavior in the bull-headed dung beetle Onthophagus taurus . Larvae exposed to dung containing ≥0.5 mg g −1 TPU microplastics experienced high mortality, whereas exposure to 0.1 mg g −1 TPU did not significantly increase mortality risk relative to controls. Despite these strong effects on larval survival, adult females were equally likely to provision offspring with TPU-contaminated (and lethal) dung as with uncontaminated control dung. This suggests that females cannot differentiate between highly toxic microplastic-contaminated and uncontaminated resources. Together, these results indicate the potential for severe negative impacts on dung beetle populations if TPU microplastics persist and accumulate in agricultural environments. However, environmentally relevant exposure levels remain unknown. Future work should quantify microplastic concentrations in the field, test the effects of microplastic composition and size distribution, and identify the mechanisms underlying TPU-induced toxicity. These avenues will be critical for evaluating the long-term consequences of microplastic pollution for insect–mediated ecosystem functioning.