Muskrats: A canary for the wetlands coal mine?

The loveable muskrat - once considered the “bread and butter” of the fur trapping industry, has been utilized for both their hides and meat by fur trappers for hundreds of years. While historically coveted by North American trappers, the semi-aquatic rodent hasn’t garnered much interest from other faucets of human society. That is, until more recently.

The muskrat (Ondatra zibethicus) is known to inhabit marshes, brooks, lakes, ponds and miles of ditches and streams across a wide range of climates. During North America’s “fur boom”, fashionable garments of muskrat fur were sometimes sold under the moniker “Hudson Seal” to entice a more luxurious appeal. Their soft, naturally water repellent fur coats are durable and insulating.

During the 1800’s, citizens could take to the local marshes and invade identifiable muskrat huts to collect the rodents for edible protein. Thanks to a long-standing permission, Catholics in Detroit are given dispensation from the church to eat muskrats on meatless Fridays during Lent.

For a time, muskrat meat could be found on the menus of the most upscale restaurants on the east coast - with the tender, dark meat often advertised as “marsh hare” to otherwise unsuspecting patrons. Today, muskrat meat, which is comparable to duck, is still a common fare in parts of greater Maryland and blotches of the mid-Atlantic United States, where the tradition of trapping, skinning and preparing the rodent for a meal lives on.

Personally, I prefer my muskrat hindquarters prepared in a frying pan with a fresh onion and a little olive oil - beyond that, I haven’t ventured further into the other countless ways to braze, bake, or roast the small furbearers.

Some have contended that due to the muskrat’s popularity with trappers (both experienced and novice) - many of America’s local marshes would cease to still exist had it not been for the value placed upon muskrats as both a food source and a fur resource.

A Noticeable Decline

For the last 25 years or so, trappers throughout the Midwest and Northeast have raised the flag on a noticeable decline in muskrat populations. In places like Pennsylvania, for example, the ‘rat harvest declined from 720,000 in 1983 to 58,295 in 2010. Studies have found that it isn’t just a decline in pelt value causing decreased population records - although biologists do caution that a decline in trapper participation and interest should be heavily factored when counting through yearly harvest reports. While experts have noted the regulated trapping community isn’t to blame, there seems to be quite the array of suspicion as to what has caused the muskrat decline.

Everything from chemical use on agricultural farms, to field tile spacing, to pharmaceutical contamination, to harmful metals have bore suspected blame.

Susie Prange, Furbearer Biologist for the Ohio Department of Natural Resources, Division of Wildlife summarized in 2016 that pesticides and personal care products showed up in minor amounts in some of the 592 donated muskrat carcasses from across Ohio.

Those muskrat carcasses (many submitted by licensed trappers) were examined for age, sex ratios, female reproductive output, organ health, and most importantly, exposure to contaminants. Heavy metal presence was significant - with 40 of the 41 animals tested for metals showing moderate to severe levels of metal contamination and exposure above threshold levels for 1-to-18 elements. Most muskrats across the state suffered from exposure to six widely-used metals including antimony, calcium, iron, mercury, molybdenum and strontium, while three muskrats had exposure to 17 or 18 different metals. Prange noted that this kind of contamination “can have negative effects on health, survival and reproduction.”

Liver lesions, consistent with tapeworm larvae, were also detected in low levels of some specimens.

Other researchers have gone as far as to suggest we may have cleaned up our rivers and streams a little too well - causing the removal of algae and other plant-life in trade for squeaky-clean rocky-bottom river beds.

Pennsylvania furbearer biologist Tom Hardisky theorizes that before stricter environmental regulations were enacted, more nutrients leeched into water sources - sparking growth of aggressive aquatic plants. It would explain why farmlands traditionally equated to high-quality muskrat habitat. As protection regulations on groundwater entering water environments placed emphasis on cleanliness throughout the decades, the plant growth in these areas become less abundant - resulting in the loss of once high-quality muskrat habitat.

Still, some believe the muskrat’s decline is naturally driven - either by cyclical population cycles, disease outbreak, wetlands drying up, and/or the noticeable increase in predators such as raptors, mink and river otters.

Despite the noticeable decline, professionals in many states continue to assert that the species isn’t in danger of shifting to threatened or endangered status at this time.

Of ‘rats and wetland health

The Wildlife Ecology Institute has recently announced new research being conducted to dive into the ‘rat’s potential role as an indicator species for wetland quality in the Great Lakes Basin.

According to The Wildlife Ecology Institute’s website, the most recent muskrat project seeks to “explore the relationship between muskrat abundance and wetland condition, including to assess the value of the muskrat as an indicator species for wetland quality, connectivity, and associated wildlife in the Great Lakes Basin”.

Researchers are reviewing multiple sources pertaining to muskrat population data, such as state trapper reports and counts on muskrat huts, and comparing those data sets with that of wetland quality, and other sensitive wetland-bound wildlife species.

A sedated muskrat is fitted with a VHF collar. (Photo | The Wildlife Ecology Institute)

“We intend to develop models to test the reliability of using muskrats as an indicator species for wetland conditions in the Great Lakes Basin. Based on our results, we will make recommendations for implementing a consistent monitoring program to assess muskrat populations and wetland quality for the Great Lakes Basin and eastern half of the U.S.” the website states.

This isn’t the first muskrat rodeo Tim Hiller and his “wildlife ecology crew” have immersed themselves in. The Wildlife Ecology Institute is also currently involved in a muskrat transmitter project which seeks to determine the effectiveness of two different VHF transmitters on muskrats, with hopes of gathering insight for the transmitters’ potential application in larger regional research. Due to a muskrat’s oblong shape - one of the questions researchers hope to answer is whether the transmitter’s collar can remain in place while tracking the animals as they move throughout their natural habitats. The goal of the project is to help reduce uncertainty and increase efficiency associated with these methods in broader muskrat population decline research across the continent.

There’s little doubt that these two projects will greatly contribute to the ongoing enigma of muskrat population sustainability, as well as broader insight into wetlands habitat - and more importantly, how the two possibly connect.

Those of us with a hankering for the ol’ marsh hare continue to traverse the swampy back-hollers of America with bated breath.