Different anticoagulant rodenticides cause delayed mortality but rapid inhibition of faecal production and food consumption in house mice (Mus musculus)

Anticoagulant rodenticides are the primary chemical tool for managing rodent infestations in food production, processing and storage facilities. However, their delayed mode of action raises persistent concerns that intoxicated pests continue to feed on valuable commodities and deposit hazardous faeces during the multi-day latency period before death. This study evaluated the subsequent, short-term impacts of different anticoagulant baits on the food consumption and defecation dynamics of wild house mice ( Mus musculus ). While lethal effects were delayed (mean mortality: 6.7–7.6 days) and food intake remained unchanged for the first three days (declining from day 4), our novel finding reveals a rapid and marked suppression of defecation within the first 24 h of exposure. Across all three tested anticoagulant baits (based on warfarin, bromadiolone and difethialone), faecal output dropped by more than 50% on day 1 compared to untreated controls. Because this rapid reduction occurred immediately across all formulations, before lethal symptoms or reduced bait intake, it likely reflects an immediate reaction to bait composition , rather than the specific delayed toxicological mode of action of the active substances. These findings demonstrate that although anticoagulants cause mortality with a multi-day delay, primary contamination risks from faecal deposition are substantially mitigated within 24 h of bait ingestion.