What happened to all the leeches in Leech Lake?
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WALKER, Minn. — Minnesota's third-largest lake has a namesake only an angler could love: the leech.
Earthworm's ugly aquatic cousin. Those slimy, crawly creatures straight out of a horror film.
But even with its squirm-worthy name, Leech Lake has long drawn vacationers to this north-central part of the state. One regular summertime visitor, Minnetonka resident Steven Adams, wonders: What happened to the leeches?
He sent his inquiry to Curious Minnesota, the Star Tribune's community-driven reporting project.
"When my family would vacation on Leech Lake [in the 1980s], we would see fat leeches swimming in the lake," Adams said. "We no longer see any leeches."
No one is studying leech populations on the lake. Anglers report seeing fewer leeches, though some say they still spot an occasional leech in the water. So leeches aren't extinct on Leech Lake. Enough people, including me, shared Adams' curiosity for us to dive in. Invertebrate experts provided a few hypotheses about their (apparently) dwindling numbers.
Bygone bloodsuckers?
Though memories are imperfect, I can still picture, clear as day, swimming at Walker City Park as a kid and screeching over leeches suctioned to my ankles. Now, leech spottings are few and far between, residents and vacationers agreed. I posed Adams' question to the Leech Lake Fishing group on Facebook.
"We have noticed it for several years, too. We used to see the big spotted ones; maybe see 1 a year now," Ken Girard wrote.
Lyn Borchers said she has been vacationing on Leech Lake for 60 years and wonders what happened as well. Benson Ringle, a Walker native, said he's been pondering this question, too, because "20 years ago there were leeches everywhere."
Many had theories. Tate Moening wondered if zebra mussels had something to do with the apparent exodus. Mathias Mathis thought it might be over-trapping from bait sellers. Mike Johnson pondered whether the poison from mosquito control was a culprit.
"Does it coincide with the rusty patched crayfish explosion?" asked Joel Lemberg.
Jason Johnson said he saw several leeches last September. So did Harry Ekstrom, though he said, "definitely not as many as when we were kids."
Barb Post said she's been coming to the lake for 47 years, however, "and there has never been a large amount of them. I think my kids only had a few when swimming."
"I didn't know they were gone," Jeff Erickson added.
Clear as mud. But before we hear from the experts, what exactly is a leech?
Looking for leeches
Leeches are related to earthworms and share the same segmented body structure so they can lengthen and contract. They are most known for having suckers on both ends.
It was once estimated that there were 26 leech species in the state's abundance of lakes, according to the 1959 scientific journal article "A Simplified Key to the Leeches of Minnesota." There are 650 species of leeches around the world varying in shape, size and diet. Some have spots. Some are long and skinny. Others are wide and short.
Most leeches are predators. Sometimes they are parasitic. They can be used for bloodletting and bait. Anglers sometimes refer to leeches as bloodsuckers.
The Ojibwe first called Leech Lake "Ozagaskwaajimekaag-zaaga'igan," translating to "lake abundant with bloodsuckers."
On a recent afternoon, I went looking for leeches with state Department of Natural Resources large lake specialist Carl Pedersen, who has kept a finger on the pulse of the lake for two decades. His main task is checking walleye populations, which involves wading off shore with a 100-foot-long net called a seine.
After dragging the seine on the shores of Traders Bay, the net came up empty for leeches. We wandered over to Agency Bay — and voila. Pedersen pulled a fat, long gooey thing out of the water with his bare hands. He was holding a horse leech, malleable like putty and covered in a mucus-like substance.
A horse leech is greenish grey with black spots. They don't suck your blood. They prefer snacking on snails, fish eggs and tadpoles. They will even crawl out of the water and onto shore to eat their cousin, the earthworm.
Pedersen said he used to catch more leeches in the seine. He sees fewer nowadays. But that's an imperfect science. Pedersen was looking for walleyes, after all. He said low leech numbers could be the result of a number of factors, like invasive species of zebra mussels and rusty crayfish.
'There's something not right'
I shared my "finding" of one lonely leech with invertebrate zoologist Lori Tolley-Jordan, a professor at Jacksonville State in Alabama.
"If you're pulling that few leeches, there's something not right," she said. Especially on a lake as big as Leech, which spans more than 110,000 acres with 230 miles of shoreline and maximum depth of 150 feet.
To truly understand the fate of leeches on Leech Lake, researchers would have to start looking for baby leeches, Tolley-Jordan said. If there aren't any, or many, "that species is on its way out," she said.
"But the ability to detect invertebrates consistently over time can sometimes be difficult," she added.
Researchers often track fish in this way because fish are tied to tourism and the economy. The observations of fewer leeches are valid, but it's hard to see things change through time without consistent sampling.
The full extent of leeches' role in an ecosystem isn't well understood, Lori Tolley-Jordan said. But they are an important food source.
In Europe, leeches are endangered from over-harvesting and loss of habitat, she said. Lake temperatures are warming, and that can really make a difference, too.
"So leeches can be vulnerable to things," Lori Tolley-Jordan said. "It's hard to get the public to understand the significance of the spineless wonders. ... The most important part is for someone just to notice."
Pedersen said the last time he remembers seeing many leeches in Leech Lake was when the Natural Resources Research Institute in Hermantown, Minn., visited more than five years ago. "They were really just amazed by [the leeches] because they're so big," he said.
Katya Kovalenko, a research associate at the institute, was on that trip. A leech study would be useful, she said, especially since so little is known.
"I hope we have more information," Kovalenko said, "because it is the namesake for the lake."
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