Muskrats of Michigan

© Erik Zunec | Dreamstime.com

By Mark H. Stowers

Blessed by the Southeast Michigan Catholic Churches as a Lenten rescue, hailed as an ecosystem indicator, a boon to the fur industry, but can also be a bane to the existence of lakefront property owners – Michigan muskrats. For generations, these small furry nocturnal or crepuscular (active at dawn and dusk) creatures have navigated Michigan’s rivers, lakes and streams, making their homes on the banks and creating huts on the water.

Trappers have long kept a close eye on the critters and taken their pelts to market to be turned into fashionable and functional hats and gloves across the world and for Michigan Catholics, their tasty carcasses became a Lenten gathering favorite – tradition still continues, though mostly in downriver communities. Muskrats are native to every inch of North America. Their numbers are in decline, according to trappers, but trappers are also in decline so a true population number is hard to come by.

Tim Hiller, a wildlife ecologist and the founder of the Wildlife Ecology Institute, has led extensive research on furbearers. His work with the Furbearer Conservation team highlights muskrats as key indicator species, often called "canaries for the wetlands," whose population health closely reflects broader ecosystem stability. Hiller is wrapping up The Great Lakes Muskrat Project and will begin compiling all data from the study that began in 2019.

“Eight years ago, we secured funding for a project in the Great Lakes Basin, partnering with the Michigan DNR, the Fish and Wildlife Service, and a good friend of muskrat researchers at Kansas State University,” Hiller said. “I had been hearing for many years and had also experienced that muskrats are disappearing or at least declining across their distribution. The driver of this study is ‘Why are these muskrat populations declining so substantially?’ Trappers are at the forefront of this and have been deeply involved.”

Hiller has four study sites ranging from the UP of Michigan, one in Chiawassee in northern lower Michigan and then in northern Ohio.

“We chose those on a gradient of more pristine wetlands up north, going south to northern Ohio where we’re going to expect more contamination, more disturbance, more impact on those wetlands,” he explained. “We’ve collected a lot of data on wetland vegetation, like species composition and basic species, and water quality. We’ve done muskrat hut counts on each one as an index of populations in each area during each year. We’re also going to look at weather patterns, such as droughts and so forth. Although some of these areas have water control structures, they’re kind of some of them are wildlife production areas. They’ve got a little bit of control over the water level.”

In addition, Hiller and his staff have purchased nearly 1,000 muskrat carcasses from across those four areas from trappers who kept detailed logs of their trapping activities.

“Then we can use that to also index population trends. And from those carcasses, we’re looking at everything from reproductive tracts to see how they’re reproducing, body mass, and body fat content to assess health, as well as diseases, parasites, and contaminants such as heavy metals. And then from those, we’re also getting a sex-age structure of the population, so that males and females, juveniles and adults. That could help us look at whether the population’s skewed toward males, which might indicate a declining population. What is the population like? Was there a sufficient number of juveniles each year to replace them? Muskrats are short-lived, high-reproductive-capacity species, as most rodents are. You would expect more juveniles in the population each year to replace the adults that are experiencing mortality for various reasons.”

Though he is in the initial stages of sorting through the massive amount of data, he has found that muskrats are experiencing effects from contaminants, such as heavy metals, that are entering their ecosystems.

“That increases their predation risk,” Hiller said. “Muskrats are an indicator of wetlands and wetlands serve as ecosystem kidneys that filter contaminants. Are these muskrats signifying a much larger issue? It extends potentially to waterfowl and amphibians and lot of other species.”

Muskrats are “ecological engineers” according to Hiller.

“They create habitat, whether it’s nesting for waterfowl on their huts or amphibians that utilize lodge structures and create what’s called hemimarsh conditions. You might see a monoculture – a stand of cattails that completely covers a marsh. That decreases biodiversity. Muskrats feed on cattails and use them to build their lodges. They open up that water and create more habitat for more wetland species. The more functional the wetland is, the better it is for us. I’ve mentioned filtering contaminants and sediments. When we have healthy wetlands, we can credit muskrats largely to much of that.”

When muskrats are not building huts, they can become destructive or a nuisance to lakefront landowners, according to Hiller.

“Where they don’t build lodges, they dig tunnels, and when they dig tunnels on lakefront properties or golf courses, those tunnels collapse. That caused some issues for the property owners. So, there is a balance there too, where it’s not perfect in that they don’t cause damage. It’s what the tolerance of the individual landowners is in those cases. And that could be a safety concern if you’re mowing near the edge of your lake and a tunnel collapses. That’s not a good thing. There can be a trade-off there as well,” Hiller said. “The only pragmatic solution for something like that is periodic removal. If it’s in a lake, it isn’t necessarily an ideal location for a muskrat, like a wetland with cattails. Presumably, there’s going to be some shallow areas of the lake where they’ll persist just fine. And hopefully, not create problems for the landowners. But if landowners so choose, they can trap at no cost. Or there are animal damage control folks that are professionals that can them as well, which might be the reality that we live in. Lakefront property owners can place riprap on the banks and several feet below the water line to discourage digging by muskrats. That might be a longer-term solution.”

Muskrats have been known to damage boats and docks. The Michigan Lakes and Streams Association encourages lakefront property owners to “install a muskrat guard on your boat. These install in the exhaust and have threaded bars that can be adjusted to hold it firmly in place. At $245 to over $400, depending on the size of your exhaust, they’re pricey but a lot cheaper than replacing your boat. Note: many insurance policies typically exclude damage caused by ‘vermin,’ which includes muskrats – riparians should check their coverage and consider working to getting muskrat damage covered if there is a problem in your area.” Also, the use of predator urine – mink, coyote, or bobcat – available from trapper supply outlets and over the Internet) or ammonia can help deter muskrats as well from docks and boats and shoreline areas.

Some basics of muskrat life include the rodents being found in all of North America and, according to Hiller, their reproductive patterns vary by climate. In a southern, warmer climate, Muskrats can have up to three litters per year, from March to October, and their gestation period is around 25 days.

“A northern climate, it might be one to two. I think there are some years that they’re going to have two successful litters, and again, the number of kits they have in a litter, and the number of litters they have is all tied to the conditions at that time. If there’s a lot of food, the weather’s good, and so forth, their litters are going to be larger. Maybe five or six individuals, kits maybe more. If it’s not so good, they might have two to three.”

Muskrats are active and both male and female share in all of the duties, according to Hiller.

“They’re always maintaining their huts and patching things up, and they’re typically very active,” he said. “When it gets cold and the hut ices up, they’re still there going after underwater stashes of food, doing the muskrat thing. They’re active year-round.”

Sean Zara, Wildlife Program Coordinator with Oakland County Parks, regularly sees muskrats in his day-to-day business.

“They are considered to be a pretty common species and sometimes considered to be a nuisance,” Zara said. “Their overall appearance is that of a beaver but they are not related to beavers though they’ve adapted independently to an aquatic lifestyle. They are actually giant voles. They do some of the same things as beavers and some things not the same. They build some types of structures but not others. They don’t build dams, which means they’re not nearly as much of a nuisance for infrastructure as beavers because they don’t cause flooding. But they dig burrows into the banks of wetlands. And so they are considered a nuisance on wetlands where the water level is controlled by dikes or berms, or any sort of earthen structure that’s holding water back, because they will burrow into those and weaken them. They can potentially cause collapse of any sort of earthen structure like that.”

In Zara’s previous line of work, he conducted surveys on constructed waterfall ponds and there was a constant battle with muskrats who burrowed into them.

He noted that like beavers, muskrats build lodges or huts but not out of logs.

“In order to have themselves a safe place to hang out, stay dry and live, they don’t chew down trees or shrubs or anything, they only go after herbaceous vegetation. They’ll make a lodge out of like cattails and reed stems,” Zara explained.

In addition to their huts, muskrats will create their own feeding platforms as they do not hibernate and are active year round.

“They make feeding platforms that are a mound of vegetation tall enough for them to sit on above the water and dry out and have a vantage point to look for predators. Those are definitely important to many other wildlife species. I commonly see goose nests built on top of those because they provide a nice little dry platform,” he said. “And then the other thing they do is build things called push-ups. Basically, what happens is muskrats don’t hibernate; they’re active all winter and they don’t store food. They have to be out and about, looking for food all the time all winter. If the lake is frozen over, they’re going to be swimming around under the ice. When the water first starts to freeze over, they’ll chew some holes through the ice and cut some cattail leaves and dead herbaceous and stuff them in the hole to help keep it from freezing over again. They’ll do that repeatedly over the winter, keep coming back to the air holes they’ve made, and keep shoving dead plants into them to keep them from freezing. They will eventually make these little mounds that stick up through the ice during the winter. And there’s just enough space for a muskrat to fit through the hole in the ice and get up inside of this little mound of vegetation, and it’s sort of like a mini version of a lodge.”

The advantage of muskrats collecting vegetation is two-fold. Cutting and eating cattails opens up marsh areas for themselves and other animals. They also are eating invasive plants and eliminating them as they cut them down underwater, and the invasive plant actually dies.

“From that perspective, people like open water, so muskrats are the opposite of being a nuisance,” Zara said.

Muskrats fill an important part of the ecosystem food chain as a smaller furbearer; they and their young are often prey for any larger carnivore.

“Up to and including maybe even large fish,” Zara said. “I would say that we have muskrats in every wetland situation that is at least somewhat marshy. They’re not quite as amenable to a strict open water with no emergent vegetation because that’s their food, but we certainly have them in every Oakland County park. They are one of our more common large mammals. People see them during the day, and they’re more familiar with the concept of a beaver than a muskrat, so they see them, and ‘Oh, it’s a beaver’ or ‘Oh, it’s a baby beaver.’ They really are a generalist, do-it-all kind of creature. They mostly eat vegetation but they’ll eat almost anything if forced to. They’ll live in almost any sort of situation. They are one of the relatively few large animals willing to live in a retention pond, or a completely artificial aquatic environment. Just because they are so adaptable.”

Zara explained to distinguish a muskrat from a beaver, look for the tail in the water.

“Muskrats have their relatively slender tail that’s flattened side to side. When they swim, they undulate their tail from side to side like a snake. Versus the beaver that is mostly swimming with the combination of the legs.”

Lauren Eaton, Monitoring Manager for Friends of the Rouge, hasn’t done muskrat research but sees plenty of the mammals during her work and understands their presence is a positive one. She described the program work where muskrats are part of the landscape.

“Our mission is to restore, protect, and enhance the Rouge River watershed,” Eaton said. “The Friends of the Rouge does a lot of green infrastructure work, capturing stormwater, managing stormwater, and providing habitat through rain garden plantings and tree plantings. With our paddling program, we offer many wonderful paddle trips on the lower branch of the Rouge River year-round. It gives folks a chance to go out and experience the river and paddle on the river.”

The Friends of the Rouge are creating a twenty-nine-mile water trail that was given state designation. As director of the monitoring program, Eaton is in the water quite a bit.

“We are the folks in the water doing a lot of the sampling and the testing. We have a benthic macroinvertebrate survey that we get our volunteers out with us three times a year, so it’s a great event. We have a frog and toad listening survey that is actually ongoing right now where folks go out and listen for frogs and toads because they’re a great indicator of wetland habitat. We have our fish community survey that’s been going on for over a decade. We do various water quality testing and have done some invasive species work in the past.”

Her works keeps her connected to the Michigan muskrat and she keeps a close eye on the ecosystem indicator.

“They are a type of native animal and they are semi-aquatic. They’re a mammal and they love to be in the river. A couple of cool facts about them are that they are adapted to life in the water. They have this very soft, really thick waterproof fur. And they have a clear eyelid that acts like built-in swim goggles. Also, their back feet are webbed, which helps them swim through the water. Their tail is flattened, kind of opposite of a beaver tail, flattened top to bottom. They use it more like a rudder as opposed to a beaver, which has it more like a paddle. They’re much smaller. Muskrats are usually around two to four pounds, and beavers can be much larger, about 40 to 60.”

She noted that the mostly herbivore mammal, “feed on a wide variety of vegetation that can include cattails, most of all, but can also eat a wide variety of other vegetation.

“One thing that I thought was interesting is that they can also eat European frog bit. That’s an invasive plant that we actually did a study on a couple of years ago. It’s a good thing that they’re eating this aquatic invasive plant, because sometimes invasives will come in and they won’t have any kind of natural predator or anything to harvest them.”

With the Rouge River, Eaton sees more muskrats burrowing in the bank than building huts but the “river rats” active lifestyle is quite beneficial to other plant life and wildlife.

“Because muskrats are active all winter long, they help recycle a lot of nutrients in the ecosystem. They create conditions that benefit the surrounding environment for birds, fish aquatic bugs and amphibians. We’re all about trying to restore, protect and enhance the Rouge River watershed. We’ve lost so many wetlands in our watershed, and we span Oakland, Washtenaw and Wayne County. In Wayne County, we’ve lost over 90 percent of our wetlands. If we’re seeing less stress and they’re creating favorable habitat for the other things that need wetlands and can thrive in wetlands, that’s a good thing.”

Zach Cooley, Michigan Department of Natural Resources (DNR) Biologist or Wayne, Monroe and Lenawee counties, works at the Point State Game Area, a managed waterfowl area on Lake Erie, and was destined to have a career working outdoors. His father was a pathologist and his grandfather was a biologist for the wildlife division. He’s been with the DNR for the past 17 years and works quite a bit with muskrats and waterfowl and all things wetlands as he covers five game areas, three of them being coastal wetlands.

“They’re pretty much everywhere. Ours are considered the Great Lakes muskrats. And if you talk to trappers, it makes a difference in the fur quality,” Cooley explained. “There’s just something about the Great Lakes muskrats that they’re a higher grade for the most part across the board. They’re an indicator species of water levels that don’t fluctuate a lot. Water fluctuation is a good thing, but when it happens too much too fast, it can cause problems with vegetation establishing and the animals that use the area. You want to have fairly constant water levels. They like to have pretty stable water levels.”

He noted that muskrats are “great in wetland maintenance and you are always looking for a hemi-marsh, 5 percent vegetative cover and 50 percent open water. And they’re a big key player in making that possible,” Cooley said.

Muskrats have been on the decline for several years, but the decline hasn’t been as noticeable because fewer trappers have been bringing in data. In the 1980s, there were 14,000 trappers targeting muskrat, and they were taking over 700,000 muskrats in a year. There was a resurgence of trappers in the 2010s with more than 24,000 registered fur harvesters but not all of those actually go out and trap. Currently, there are 3,000 trappers, and taking about 150,000 muskrats.

“The population overall is on the decline. It has been for a number of years. It’s hard to notice as much because the number of people trapping and harvesting them is going down,” Cooley said. “We’re not over-harvesting them, but their long-term population is in a slight decline.”

He pointed out the decline most likely is due to the loss of wetlands.

“Muskrats are 100 percent dependent on wetlands, they spend their whole life in wetlands. That’s why the Catholic Church blessed them and back in the day you could eat muskrats during Lent because they spent their whole life in the water. When wetlands are filled in or destroyed or polluted and compromised, they lose that habitat.”

For trappers, the work is usually not worth the pay as raw, unskinned pelts are averaging $2 but buyers are hard to find.

Cooley explained more about the huts that muskrats create to live in.

“They’re made out of mostly vegetation and mud, mainly cattails and mud. They build low mounds that come up out of the water, and the inside of the mound is a little house area that gets them out of the water. But their entrance is almost always in the water somewhere, so they swim up into it,” he said. “The huts can be anywhere from maybe only two to three feet across to big ones can be five feet across and five feet out of the water. It just depends on how long they’ve been there, how old the hut is.”

He noted the huts are where the litters are raised but muskrat parents are quick to raise their young ones.

“They’re good parents, but then they push them out and make them go through the motions of finding their own territory within that first year. Muskrats can be really territorial. They fight a lot,” Cooley said. “And that’s an issue that trappers have if there are too many muskrats in an area. They get pretty beat up from fighting with each other and damage the fur and hide.”

Being part of the food chain, “Muskrats do have predators, and they’re vital to the wetland and the ecosystem in that way as well,” Cooley said. “Again, there is a lot of them. Mink and otter, coyotes, fox, even raccoons and some raptors will go after them. Like eagles and hawks. They get it from all angles for the most part. But that’s just part of them being a cog of a wetland, supplying that food source.”

But when there isn’t the balance of predators to keep them in check, lakefront areas can suffer the consequences, according to Cooley.

“Stream banks and those kinds of areas are where they will burrow and live in the banks and in the lake shore. You don’t want them in those areas that as they’ll cause problems, But they can fill and take over an area and be overpopulated if they’re not kept in check you can run into some diseases with them,” he said.

If muskrats are a problem, Cooley recommended contacting the Michigan Trappers and Predator Callers Association, “which has a program where they will help landowners control, especially fur-bearing animals. They prefer to do it during the season when the furs are good.”

But overall, Cooley noted, “Muskrats are a good thing to have around and to see. You want to have a good population. You don’t want to get too many of them and have them take over an area. Just because you see them, it’s not a bad thing. It’s a good indicator species that the wetland and water source are healthy. They’re fun to watch. They’re not aggressive. They’re not going to come after you or anything. For the most part, They are very scared of you, and they will turn and head under the water as soon as they see you. They’re just they’re fun to watch. They’re fun to have around.”

Cody Norton, Bear, Furbearer, and Small Game Specialist with the Michigan Department of Natural Resources Wildlife Division, works in Michigan’s Upper Peninsula. He explained that much like how a beaver can change the habitat of an area by building dams, muskrats are “considered ecosystem engineers as they can actively change and maintain the habitat around them impacting other species on the landscape. They can open up a dense area and make it more usable for waterfowl and fish and in some cases reptiles and amphibians.”

The huts that they build can also be beneficial to other aquatic life.

“They create an underground chamber in the bank, and the entrance to that or multiple entrances will actually come out below the water line. If you are standing on the bank over top of one of these, if the water’s clear enough, see maybe a dark pond bottom or marsh bottom, and then you’ll see this light swath coming out from the bank and going into deep water, and that’s from them dragging sediment as they go in and out of their underground tunnel,” Norton explained. “They’re going to erode the water bottom underneath them and that can actually end up with fish being able to access parts of a marsh that they otherwise wouldn’t be because it makes the water deeper in those channels.”

He noted that, “Ducks and rails will follow those into different areas, too. The huts that they make out in a marsh complex or in a pond or lake, if they aren’t banked, they’re raised up above the water and you could see any predator coming. Geese, swans, and mallards will actually nest right on top of a muskrat hut. Actually, they provide nesting areas for mink and other small mammals if they abandon their huts. Mink will actually den in them.”

Norton explained the muskrat hide can tell a long story.

“You can generally tell from the hide, from the patterns on the inside of the hide, whether a muskrat is a juvenile born that year or if it’s an adult. Past that, you can look at a larger size versus a smaller size, but that might not necessarily translate to age. It could just be that it’s a productive area in general. I think they’re thought to be two to three years old is probably a pretty typical extent of how old you are going to have muskrats out on the landscape,” he said. “We survey trappers at the end of every season. Sending out about five thousand surveys to a random subset of all of our fur harvester licensed buyers. Through that, we ask them if they pursued each species, including muskrat. If they did, how many days did they spend pursuing them? How many traps did they use per day on average? How many muskrats did they catch? And so that allows us to get different trend indicators for what the population is doing, as well as understand how harvest reacts to those changes in season length or other management actions.”

Norton explained for trappers, “It’s probably a little bit more work nowadays than it was during the fur boom, when there might have been more fur outlets and more opportunities for people to sell. The Michigan Trappers and Predator Callers Association is a statewide trapping group. There are also a couple of other groups in Michigan in the U.P. They host two, maybe three, fur sales a year. Basically, they host sales where you can go in, bring your fur and actually watch people bid on it and buy the fur to use.”

He also explained some nuisances of muskrats, such as “if you have really small culverts or drainage pipes, they can end up either intentionally or unintentionally plugging them with cattails and things they’ve maybe discarded, or that got washed out in a rainstorm away from the hut or push up like that. In some areas, when the water level drops low, they might intentionally block it, similar to a beaver building a dam. More commonly than that, for issues we see and deal with, are tunneling. Basically, that bank den behavior they have where they’re tunneling into the ground. They’re making these underground burrows. You can have that along dams, dikes, levees, and if you are a homeowner on a lake and you’ve got a nice shoreline, they’re going to dig into that potentially, if you have good habitat around it, and that can cause erosion too. You might have a step near the shoreline and your foot goes down into a muskrat hole. We’ve heard of people at golf courses mowers trying to mow along a pond or a water feature, and all of a sudden, the mower’s tires drop in and they’re stuck or in danger of tipping. I’d say those are certainly impoundments that are meant to hold water back to create a lake or pond or water structure, or just people’s shorelines that get eroded away because they’re creating those bank bends under. The grass, or whatever their shoreline’s made up of.”

The delectable side of a muskrat is just that. The Detroit area has a long history of Catholics eating muskrat during Lent. Strict Lenten requirements at the time, combined with harsh winters that left very little food because thick ice covered area lakes, made fishing nearly impossible. During these early years of the 19th century, the pastor of Ste. Anne Parish in Detroit, Father Gabriel Richard, lobbied for a special dispensation allowing the region’s residents to eat muskrat throughout Lent. Fr. Richard frequently served as a missionary priest to Monroe County’s Catholics and would have experienced their food-related problems firsthand. This unique dispensation cemented southeast Michigan’s rodent-eating reputation. Ever since, muskrat dinners have become a common occurrence both in the Downriver area and Monroe County. These dinners once drew hundreds of diners, but these days they draw fewer than 100, and the tradition still continues. 

The original meal preparation was a three-day plan that began on Wednesday, when the muskrats were cleaned and the fat removed, then the musk was removed from the back legs. After the initial cleaning, they are salted and put on ice. The muskrats are cleaned two more times, once on Thursday and then on Friday to prepare for the cooking which entailed being parboiled with onion, spices and celery and then fried in a pan. The dark meat delicacy is still a Lenten tradition. If interested, look for the recipe listed below.

Blessed and necessary but sometimes a nuisance, the Great Lake muskrat serves several purposes in the Michigan ecosystem. ­ ­­­­