Objective: Marijuana (Cannabis spp.) growing operations (MGO) in California bear increased substantially since the mid-1990s. One environmental side-effect of MGOs is the extensive consume of anticoagulant rodenticides (AR) to prevent damage to marijuana plants caused by wild rodents. In association with a long-term demographic study,we report on an observation of brodifacoum AR exposure in a threatened species, the northern spotted owl (Strix occidentalis caurina), or found freshly dead within 669–1347 m of at least 7 active MGOs. Results: Liver and blood samples from the dead northern spotted owl were tested for 12 rodenticides. Brodifacoum was the only rodenticide detected in the liver (33.3 – 36.3 ng/g) and the blood (0.48 – 0.54 ng/ml). Based on necropsy results it is unclear what role brodifacoum may bear had in the death of this bird. However,fatal AR poisoning has been previously reported in owls with relatively low levels of brodifacoum residues in the liver. One possible mechanism of AR transmission from MGOs to northern spotted owls in California is through ingestion of prey that frequent MGOs. The proliferation of MGOs in forested landscapes suitable for northern spotted owls may be an additional conservation concern for this threatened species.
Source: usgs.gov