Don’t Eat the Mice! Rodenticides in Furbearers

DEC Seeking Harvested Fisher and Gray Fox Carcasses

Have you ever used rodenticides to get rid of pesky mice on your property? If so, you’re not alone. The use of rodenticides to control rodents has become increasingly common, with anticoagulant rodenticides (ARs) being the most frequently used. These compounds inhibit the blood clotting abilities of rodents, leading to internal bleeding and death. But other animals aren’t immune to the impacts. Anything that ingests ARs is at risk. Exposure can be through directly ingesting the poison or feeding upon another animal that was exposed. Since rodents that consume ARs do not die right away and often exhibit slow, abnormal behavior prior to death, they make easy prey for hungry wildlife. Large doses of ARs can kill wildlife directly by causing them to bleed excessively from relatively minor trauma. Smaller doses may not kill them directly, but likely has sublethal impacts like making animals more susceptible to diseases or impacting reproduction.

How common is AR exposure in wildlife? As it turns out – very common. Anticoagulant rodenticides have been documented in a wide variety of birds and mammals across the U.S. In New York State, researchers at SUNY-ESF and Cornell University tested over 100 trapper-harvested fishers for the presence of ARs. Over 80% of the fishers were exposed to at least one AR compound, with over 50% being exposed to multiple compounds. Foxes also seem to be particularly vulnerable, with 100% of red and gray fox samples from New Hampshire testing positive for AR presence.

How can you help?

DEC has partnered with neighboring state agencies and researchers to better understand the impacts of anticoagulant rodenticides and other toxins on our wildlife. We will be collecting fresh carcasses of fishers and gray foxes to conduct comprehensive health screenings on this fall. If you have a fresh carcass that you are willing to contribute to this study, please reach out to your Regional Wildlife Office or e-mail [email protected] for more information. Anyone who contributes to the study is eligible to receive a Furbearer Management Cooperator patch!