Assessment of anticoagulant rodenticide exposure in six raptor species from the Canary Islands (Spain)

Abstract

Anticoagulant rodenticides are highly toxic compounds that are widely used for pest control of rodents, but that also may threaten the wildlife's health. This work aimed to assess the exposure to first- and second-generation anticoagulant rodenticides (ARs) in six birds of prey species from the Canary Islands (Spain). The concentrations of seven widely used ARs were determined by LC-MS/MS in 104 liver samples of six species of birds of prey (Buteo buteo, Accipiter nisus, Falco pelegrinoides, Falco tinnunculus, Asio otus, and Tyto alba). We determined that 61% of the livers had detectable residues of at least one AR. The most frequently detected AR was bromadiolone, which was detected in 603% of the positive cases. The detection frequencies of these compounds varied widely, depending on the species. More than 75% of the A. nisus, T. alba, and A. otus individuals had detectable rodenticide residues in the liver. However, F. tinnunculus exhibited the highest concentrations of AR, with median values above 100 ng/g w.w. We did not detect first-generation ARs in any of the samples. When grouped, nocturnal species exhibited higher AR concentrations than diurnal species (P < 0.001). The residue levels were higher among small mammal-eaters than bird-eaters (P < 0.01). While most animals exhibited no macroscopic signs of coagulation disorders, approximately 35% exceeded the threshold levels of toxicity, which suggests that these compounds could weaken these animals in their natural environment. In conclusion, the control of rodent populations by ARs suggests that these compounds will enter the food chain and thus threaten the vulnerable populations of raptors on the Canary Islands. Our findings require authorities to ban or strictly control the use of these rodenticides in the natural environment for the conservation of raptors and other predatory species.