The number of muskrats trapped for their fur in Minnesota dropped last year to about 19,000, the lowest on record.

Biologists say a number of factors are at play in that drop, including fewer trappers. But it may also reflect the semiaquatic mammal's long-term decline in much of the country, including Minnesota, that experts say is tied to the loss and erosion of wetland habitats muskrats need to survive.

People still see muskrats in lakes, streams, marshes — even drainage ditches — but trapping data are the only regular measurements of muskrat populations in Minnesota. Muskrats have received little attention from researchers, though they're likened to bison in the importance to their landscape.

Muskrats have declined across the country since the 1970s, although the dropoff is most significant in the southeast United States, according to Adam Ahlers, a wildlife ecologist at Kansas State University who researches muskrat.

"They're kind of like ghosts moving across the plane between water and air," Ahlers said. "We just see them for a split second. If we lose them, we lose a charismatic creature that's been doing great things for us."

Not considered endangered or threatened, the population of muskrat in Minnesota likely numbers in the "hundreds of thousands," said Minnesota Department of Natural Resources (DNR) furbearer research biologist John Erb.

Taking into account the number of muskrats trapped per attempt, data suggests Minnesota muskrats have been "fairly stable" over the past 17 years, despite the number trapped declining from 243,360 to 18,890 during that time, Erb said.

Erb chalked the drop to low fur prices, weather, trappers retiring and the possibility of fewer animals.

With concerns percolating, muskrats grabbed the top spot at the virtual meeting of the DNR's furbearer committee in August, focused on new research priorities. The group works with a host of mammals targeted for their fur, including coyotes, bobcat, martens and otters. Now they're mulling how to help muskrat thrive.

Walt Gessler, manager of the DNR's Lac qui Parle Wildlife Management Area in western Minnesota and a member of the furbearer committee, likened muskrat to bison.

"Think about how important bison were to the prairies. … Muskrats can be that way too, to wetlands," Gessler said.

Trapping records show the most muskrats ever harvested in Minnesota was nearly 2 million in 1943. That could have something to do with food rations restricting meat during WWII.

The U.S. government promoted muskrat for dinner with a 1943 leaflet "Recipes for Cooking Muskrat Meat," from the U.S. Fish and Wildlife Service out of Chicago. Erb has a copy pinned above his desk.

The leaflet proclaims muskrats as a "game worthy of an epicure." It features multiple recipes including one for pickled muskrat and one called Maryland Shredded Muskrat.

Times have changed. Andy Shoemaker, a retired police officer and long-time trapper in May Township near Stillwater, said he thinks most Minnesota muskrats are harvested for fur coats and fur-lined hats and gloves, among other garments. Shoemaker considers the fur very beautiful, with seven or eight colors in a single pelt. There's a big international fur auction house in Ontario, he said, and large fur markets in China, Russia, South Korea and Japan.

Shoemaker said he suspects the muskrat decline is linked to the resurgence of major predators like bald eagles.

While no one knows what's causing the long-term decline, Ahlers said he suspects the loss, isolation and degradation of wetlands.

Erb agreed. The tiling of farmland to drain wet areas is also a likely factor, along with the climate-change-driven volatility of floods and droughts — extreme changes that can make life hard for muskrats, he said. Muskrat habitat is also vulnerable to invasive or exotic species such as carp and hybrid cattails.

A drop in muskrat population has been noticed by Darren Vogt, resource management division director at the 1854 Treaty Authority in Duluth, governed by the Grand Portage Band of Lake Superior Chippewa and the Bois Forte Band of Chippewa.

Vogt said tribal elders and ricers taught him that muskrats signal healthy wild rice stands, so central to Ojibwe culture. He's heard them described as "cleaners or gardeners of a lake." It's thought the mammals help wild rice by stirring up sediment and controlling other vegetation like cattails, watershield or pickerelweed.

Muskrats also hold a central place in an Ojibwe creation story as a humble and brave creature that, following a great flood, swam down to bring life-giving soil to the surface, he said.

Muskrats are much smaller than beavers and don't live nearly as long. They don't eat or tear down trees, or build dams that cause flooding like beavers. They build smaller huts out of plant stems, and also make homes by tunneling into banks along lakes or streams.

Mink and raptors will eat them — even a pike will take them, Erb said.

"Everything likes to eat a two-pound furry little hamburger," said Steve Windels, a wildlife biologist at Voyageurs National Park.

Windels recently experimented with muskrats' potential to control the hybrid cattails choking out other plants in Voyageurs National Park. The aggressive hybrids are formed by non-native narrow-leaf cattails crossing with the native broad-leaf cattails. Mats of hybrids can break off and float around, colliding with houseboats. One mat measured about 10 acres, Windels said. Chemicals are restricted in the park so staff are left chopping some up by hand. Nobody wants to deal with them.

"People that are outside the park push them into the park, or they push them into Canada," he said.

The muskrat project was a bust. There weren't enough of the critters, and those they sent out either died or went somewhere else.

It's not just a problem at Voyageurs. Why muskrats aren't naturally controlling the problematic hybrid cattails around the state was discussed at the DNR meeting, said Justin Pitt, DNR assistant area wildlife manager in Bemidji. He said he's pleased muskrats are "getting a little love here."