State testing finds rodenticide compounds in all sampled fishers, most bobcats, Fish & Wildlife tells committee

Vermont Fish and Wildlife Department officials told the Agriculture, Food Resiliency & Forestry Committee on Oct. 12, 2025, that liver tests of trapper-submitted carcasses collected from 2018–2022 detected anticoagulant rodenticide compounds in every sampled fisher and in the majority of sampled bobcat carcasses.

The finding matters because anticoagulant rodenticides (ARs) interfere with vitamin K–dependent blood clotting and can suppress immunity or reproduction; agency scientists warned that those sublethal effects, combined with other stressors, could pose longer-term risks even though no statewide population declines have been detected so far.

John Austin, director of the Wildlife Division at the Vermont Department of Fish and Wildlife, said the department shares the committee’s concerns about rodenticide presence and is working with the Vermont Agency of Agriculture, Food and Markets. "The overall goal is to come up with strategies that are effective at minimizing risk of exposure of these substances to wildlife," Austin told the committee. Rhee ("Bree") Furphy, the department’s furbearer project leader, presented the sampling and laboratory results and answered legislators’ questions.

Agency testing covered trapper-derived carcasses submitted under a rule that requires harvest turn-in for fisher, otter and bobcat. Furphy said the department sampled 71 fisher livers and 29 bobcat livers from three trapping seasons (2018–2022). "Every single one of those fisher had exposure to at least one or more rodenticide compounds," Furphy said. She told the committee that bobcat samples showed exposure in the majority of cases but not every individual.

Furphy explained the department uses liver tissue because these compounds bioaccumulate there and provide a longer-term record of exposure than blood, hair or feces. Laboratory results reported compound detections measured in parts per million; the presentation highlighted two compounds detected most often in the region, including the second-generation anticoagulant brodifacoum and first-generation compounds commonly associated with consumer products (e.g., D-Con–brand formulations). She also said the neurotoxic rodenticide bromethalin was not present in the earlier study but will be tested in forthcoming sample batches.

The department and a graduate-student coauthor placed higher exposure risk in the "wildland-urban interface"—areas where houses and rural lands mix—based on predictive modeling and harvest-location data. Furphy said the modeling shows southern Vermont as a relative hotspot but that risk extends beyond state lines; the department has shared data with Maine, New Hampshire and New York and participates in a regional effort to compare results.

Committee members pressed agency staff on sampling and representativeness. Furphy and Austin said annual trapper submissions typically range from roughly 100 to 150 fisher carcasses; the 71 fisher samples represent multiple seasons but are a subset of annual harvests. The department keeps harvest-town information for submitted carcasses and can analyze geographic trends in exposure, Furphy said. She cautioned that many scientific uncertainties remain: lethal concentrations vary by species and individual, effects can be sublethal (for example by increasing mange or other disease susceptibility), and laboratory-style dosing studies are not feasible for wild fishers.

Legislators raised other technical questions the presentation did not fully resolve. Representatives asked whether rodenticides pass through milk or the uterus to offspring and whether domestic-animal studies could shed light on wildlife exposures; Furphy said definitive data on maternal transfer are limited and that species-specific metabolism and life history make direct comparison difficult. Senator Barney and others asked whether otter, muskrat or other semi-aquatic species had been tested; Furphy said otter samples had been collected and batched for testing but that results for additional species were not yet available.

The department described ongoing work and next steps: continued long-term monitoring of trapper-submitted livers, a planned batch of samples to be sent for analysis with results expected by the end of the year, and collaboration with the Agency of Agriculture, Food and Markets to develop a task force to identify strategies for reducing wildlife exposure. Austin said the department will provide updates to the committee and can return to testify as new results emerge.

While the tests show widespread exposure in the sampled carcasses, Furphy emphasized that the department has not detected a population-level decline in fishers or bobcats in Vermont to date and that more data are needed to determine whether the documented exposures are changing over time or producing measurable population effects.

The committee did not take formal action during the hearing; members asked for follow-up information and indicated interest in future updates from the department.