Is deliberate pesticide poisoning of wildlife impacting local insect communities? Wildlife and environmental forensic investigations in southern Spain present an opportunity for collaborative entomological monitoring

In many European regions, people may use pesticides, particularly carbamate and organophosphorus insecticides, to deliberately poison wildlife in response to various resource-based conflicts. Repercussions of this largely illegal practice are well-documented in macro-scavengers (vultures). In southern Spain, our environmental agents are trained to gather evidence at suspected scenes of wildlife/environmental crime, including arthropods found at animal carcasses and prepared baits. Between 2008 and 2019, pesticide residues were detected in a subset of pooled or uniquely insect samples (n = 46 instances; 12 consisting solely of arthropods). Four carbamate pesticides and/or associated metabolites were detected: aldicarb/aldicarb sulfoxide, carbofuran/3-hydroxycarbofuran, methomyl/methiocarb, either qualitatively (thin layer chromatography) or quantitatively (liquid/gas chromatography), reaching concentrations of 3.05 mg/kg (aldicarb) and 9.98 mg/kg (methiocarb). Residues have mostly been detected in beetles, but also blowfly, centipede, woodlouse and notably, European honey bee, in a suspected case of deliberate hive poisoning.Implications for insect conservation: None of the aforementioned information is currently being recorded or disseminated for arthropod conservation purposes. We therefore aimed to (1) generate awareness of the deliberate wildlife poisoning practice as it may affect local necrophagous and associated insect communities; (2) share our process of sample collection, species identification and toxicological analyses to meet wildlife/environmental crime investigation requirements; (3) stimulate interest in collaborative studies to more systematically examine/document any potential effects of the practice on susceptible arthropods species relative to their population status and ecosystem services provision; (4) outline how this additionally gathered entomological information could also be used to strengthen wildlife/environmental forensics investigations.