A small hunter faces a big problem

What can swim like an otter, spray like a skunk and hiss like a cat? The mink! These stealthy, mostly solitary animals are common in the Chesapeake Bay watershed, but rarely seen due to their preference for nocturnal hunting.

Just like its larger cousin, the wolverine, the mink is a fierce predator. It is an opportunistic feeder that will hunt anything available, including muskrats, rabbits, birds, frogs, fish, crayfish and insects. But this doesn’t mean the mink is a villain—the wide variety of species hunted by the critter ensure that any population growing in excess will be controlled.

Muskrats, one of the mink’s favorite meals, serve the important purpose of eating vegetation to open up marsh waters, allowing more species to utilize the marsh. However, too many muskrats in a marsh will eat all of the vegetation that holds the marsh together. This is where the mink steps in, ensuring the muskrat population is controlled which balances the amount of marsh vegetation. This symbiotic relationship of just two species has an impact on all of the creatures in the marsh.

Chemical pollutants threaten the fearless mink

While the mink can fend off bobcats, foxes and coyotes, it’s particularly vulnerable to chemical contaminants. Minks eat a wide variety of prey, making them susceptible to multiple contaminants from multiple sources. And because minks typically eat one third of their body weight every day, they can accumulate contaminants quickly. The presence of minks is therefore a good indicator of environmental health.

In New York, scientists found 40% fewer minks on the Hudson River in comparison to the similar habitat of the Mohawk River. The major difference between the two rivers is that the Hudson River had high levels of PCB contamination. PCBs, otherwise known as polychlorinated biphenyls, cause a wide range of health issues for minks including decreased fertility, liver damage, skin lesions and an increased mortality rate of young minks. The impact of PCBs on other wildlife can be just as severe.

Even though PCBs have not been created in the United States since 1977, they don’t break down naturally and continue to plague the Chesapeake Bay watershed. Improvements made to wastewater treatments plants over the past thirty years—initially done to help state’s meet pollution reduction goals outlined by the Chesapeake Bay Program—have captured PCBs cycling through the ecosystem. Wastewater treatment plants are now able to capture 97% of PCBs, though the contaminants are still entering the water in other ways, impacting a large portion of the Bay. Although humans are not as sensitive to PCBs as fish and the mink, the same chemical contaminants are the reason for fish consumption advisories for humans.

The mink is a good reminder that even our most formidable predators are susceptible to an unhealthy ecosystem. As partners of the Chesapeake Bay Program continue to clean the Bay and uphold the Chesapeake Bay Watershed Agreement, the mink will have an even better opportunity to call these rivers, streams and marshes home. To learn more about this critter, visit our field guide.