Anticoagulant rodenticide exposure in endangered American badgers (Taxidea taxus) and fishers (Pekania pennanti) from British Columbia, Canada, 1998 to 2018.

Anticoagulant rodenticide (AR) concentrations in livers of 69 samples of two mustelid species, collected 1998 to 2018 from locations in British Columbia, Canada are presented. The American badger Taxidea taxus is endangered in Canada, and fisher Pekania pennanti populations are at-risk. Using a high performance liquid chromatography method, we measured liver concentrations of the following second generation ARs (SGARs): brodifacoum, bromadiolone, difethialone and the first generation (FGAR) compounds: warfarin, diphacinone and chlorophacinone in 59 badgers and 10 fishers. Of the 59 badgers analyzed, 69 % (n = 41) contained residues of one or more ARs. The mean total AR exposure was 201 ng/g (wet weight) (range: 4.0-214 ng/g) with an average of three compounds detected (range 1-6) per individual. Male badgers had twice the concentration levels as females (182 ± 300 ng/g versus 93 ± 170 ng/g). The SGARs bromadiolone (n = 33) and brodifacoum (n = 21) were the most common ARs detected. Four badgers had AR levels >1000 ng/g and eight had >500 ng/g in their livers. The highest average concentrations were from badgers collected in the East Kootenay region (FGAR: 165 ± 210 ng/g, SGAR: 295 ± 517 ng/g). Six female badgers were lactating and all were exposed to rodenticides. We found no spatial relationship between development and exposure levels in badgers. In Fishers, one juvenile female was exposed to warfarin (5 ng/g) and bromadiolone (528 ng/g), and an adult female tested positive for brodifacoum (13 ng/g). Regardless of the lower incidences of exposure, finding such high levels of SGARs was surprising given that fishers are a shy forest carnivore species.