Crawling through the muck at the bottom of Maine lakes, mudpuppies are large amphibians that were accidentally introduced to the state in 1939, and have been perplexing ice fishermen ever since.
“Surprisingly, we’ve known very little about mudpuppies until recently,” said Phillip deMaynadier, biologist for the Maine Department of Inland Fisheries and Wildlife.
In 2017, the DIF&W teamed up with the University of Maine and Colby College to learn more about this non-native species and how it’s impacting aquatic ecosystems in Maine. Now two years later, they’ve learned that the state’s mudpuppy population is thriving — and it has spread.
What’s a mudpuppy?
The largest amphibian in Maine, mudpuppies can exceed 16 inches in length. They’re salamanders, but unlike Maine’s other salamander species, they’re waterbound. Breathing through big, feathery external gills, they crawl along the bottom of lakes, streams and rivers.
In addition to being exceptionally large, they’re quite colorful. Their bodies are gray or brownish-gray with dark blue spots, and their gills are red. They have flat heads, wide tails, stubby legs and four toes on each foot.
With the scientific name Necturus maculosus, mudpuppies are also sometimes called “water dogs” due to the barking sound they sometimes make.
How they invaded Maine
Native to the Midwest, the mudpuppy was accidentally released into Great Pond in Belgrade, Maine, in 1939, by a Colby College professor who was studying them at the time.
“He imported them from Pennsylvania and had them in enclosures in the hatchery stream [connected to Great Pond],” deMaynadier said. “He did it twice, actually. They escaped in 1940, as well.”
Because this amphibian spends its entire life in the muck and its nocturnal, it easily flies under the radar. However, over the years, Maine fishermen have reeled in this frilly creature, to their bewilderment.
The DIF&W used this anecdotal evidence in the study to decide where to start their search.
Where can you find them?
To capture mudpuppies, the DIF&W used modified minnow traps baited with dog food and shiners. During the winter, they drilled holes in the ice of several lakes and ponds, then dropped the traps through the holes and lowered them to the bottom. There the traps remained for a week before being pulled back up.
With this method, researchers captured hundreds of mudpuppies. In fact, their capture rates were higher than rates recorded by any biologist in the mudpuppy’s natural range.
“They’re not just eking out an existence here,” deMaynadier said. “They’re thriving.”
Through this trapping effort, researchers verified the existence of mudpuppies in several lakes and ponds in the Belgrade Watershed. Long Pond in Belgrade and Rome had the highest capture rate, with researchers recording an average of 1.5 mudpuppies per trap, per night. And McGrath Pond in Belgrade and Oakland had the second highest capture rate, with an average of 0.9 mudpuppies per trap per night.
Other ponds and lakes in the Belgrade Watershed where mudpuppies were confirmed through trapping include Great Pond (where they originally escaped), North Pond, Messalonskee Lake and Togus Pond.
In addition, following anecdotal evidence, researchers found mudpuppies in Long Pond in Livermore, which is a part of the Androscoggin Watershed. This concerns biologists, considering mudpuppies are waterbound and therefore unable to spread to different watersheds on their own.
“Maybe they moved via the bait bucket,” said deMaynadier. “Or maybe there was a natural cause [such as a bird carrying them].”
Researchers are interested if mudpuppies have spread even further. If you’ve seen a mudpuppy in any Maine waterbody that’s not listed above, you can help the study by reporting your sighting to deMaynadier at Phillip.deMaynadier@maine.gov. Include the location and date of the sighting, as well as a photo, if you have one.
How they’ve furthered science
The mudpuppy project also presented an opportunity for UMaine researchers to expand their work with Environmental DNA, which has recently been used to track rare fish in Maine.
Environmental DNA or eDNA is DNA that’s expelled by an organism into their environment in various forms, such as shed skin cells or feces. This is then collected in environmental samples, such as soil, water or even air, and used to track specific organisms.
The mudpuppy project is “a classic example” of how eDNA can be used, said Michael Kinnison, UMaine science lead for the Maine-eDNA program and professor of evolutionary applications.
“If this was an animal that people could see readily at any time, say a bird, there’s a good chance people would be able to spot it and count it,” Kinnison explained. “Where eDNA comes in handy is when dealing with organisms that are relatively rare or difficult to find or unfamiliar to people.”
During the study, the UMaine eDNA lab worked with the DIF&W to collect water samples from bodies of water, then verify their findings based on data collected from the mudpuppy traps.
“We’re certainly getting there,” Kinnison said. “We’ve designed the lab tool. We’ve shown that it will detect mudpuppy DNA down to forensic levels — a few molecules of DNA in a liter of water. Now we’re working on how to deploy the tool in the field to use it effectively.”
In August, the National Science Foundation awarded a $20 million grant to a five-year Maine Environmental DNA initiative to further develop the technology at UMaine, Bigelow Laboratory for Ocean Sciences and beyond. One of their goals is to expand the range of organisms they can detect with eDNA. Another is to make the technology accessible to citizen scientists for monitoring.
What impact do mudpuppies have?
To get an idea of the impact mudpuppies have on aquatic ecosystems in Maine, DIF&W teamed up with Catherine Bevier, professor of biology at Colby College. With the help of her students, she dissected hundreds of mudpuppies to get a picture of what they’re consuming.
“It’s all macro invertebrates,” said Bevier. “We see a lot of crayfish and a lot of amphipods and stonefly larvae and dragonfly larvae. It’s been quite variable. I’m working right now to finish it up.”
The main purpose of studying the mudpuppy’s diet is to see if they’re eating any species listed as threatened or endangered in Maine. So far, Bevier hasn’t found any of these species in her dissections, but she has found that mudpuppies will eat taxa (or groups) of animals that do contain threatened species, such as dragonflies.
“Some of those taxa do have species of conservation concern within them, so that is something that is a little bit concerning,” deMaynadier said.
Like many other non-native species that have found their way to Maine, the mudpuppy is here to stay — at least for the foreseeable future. There’s no realistic way to eradicate the species from Maine lakes and ponds without negatively impacting the other species living in those ecosystems, deMaynadier said. But things can be done to prevent the salamander from spreading into other bodies of water.
“By learning about what ponds they’re in and sort of retrospectively mapping out their movement over the last 70-80 years, we can see how they’ve spread and which water bodies are most vulnerable [to them invading next],” deMaynadier said.
Because mudpuppies are waterbound, they can be blocked with physical barriers, such as waterfalls and dams. In addition, public outreach may play a role in preventing their spreading.
From speaking with local fishermen, deMaynadier has learned that mudpuppies are considered to be good bait for large fish like bass and northern pike.
“We could put out signage and educate anglers to the fact that it’s illegal to use them as bait,” he said.
The project is scheduled to be wrapped up in spring of 2020.