A mudpuppy is a fully aquatic salamander native to eastern North America, best known for the bushy external gills it keeps for its entire life. Unlike most salamanders, which lose their gills and move onto land as adults, mudpuppies never go through that transformation. They stay in their larval form permanently, breathing underwater through feathery, maroon-colored gill plumes that fan out from both sides of the head. Adults typically measure 8 to 17 inches long, making them one of the larger salamander species on the continent.
Why They Never Grow Up
Most amphibians go through metamorphosis: they hatch with gills, then develop lungs and transition to life on land. Mudpuppies skip that process entirely. Biologists call this “neoteny,” meaning the animal reaches sexual maturity while retaining juvenile features. In practical terms, an adult mudpuppy looks like a giant salamander larva. It keeps its flat, rudder-like tail, its external gills, and its fully aquatic lifestyle from hatching until death.
Those gills are the mudpuppy’s most striking feature. They look like reddish, feathery plumes sprouting behind the head, and they’re packed with blood vessels that pull oxygen directly from the water. The gills change size depending on water conditions. In well-oxygenated, fast-moving streams, they tend to be smaller. In warmer, still water with less dissolved oxygen, the gills grow larger to compensate.
Where Mudpuppies Live
Mudpuppies are found across much of the eastern United States and into southeastern Canada, with their range stretching from the Great Lakes region south through parts of the Mississippi River drainage and into states like Georgia and North Carolina. They live in rivers, streams, lakes, and reservoirs, favoring areas with rocky bottoms where they can hide under flat stones, logs, or debris during the day. They’ve been documented in everything from shallow creeks to deep, fast-flowing channels like the Detroit River.
They spend their entire lives underwater and are most active at night. During the day, they stay tucked under cover, emerging after dark to hunt along the bottom. In colder months, mudpuppies remain active under ice, which is unusual among amphibians. Anglers sometimes catch them accidentally while ice fishing, which is how many people encounter them for the first time.
What Mudpuppies Eat
Mudpuppies are opportunistic predators that eat just about anything they can catch on the bottom of a river or lake. Stomach content studies have found crayfish, small fish, insects, snails, mussels, leeches, and even frogs. They’ve also been documented eating younger mudpuppies on occasion. In the Great Lakes, their diet has shifted along with the ecosystem: researchers have found invasive rusty crayfish, round gobies, and zebra mussels in their stomachs, suggesting they adapt their feeding to whatever prey is available.
They hunt primarily by feel and smell rather than sight, which suits their nocturnal habits. Walking along the bottom on four stubby legs, they use sensory cells in their skin to detect movement and chemical cues from nearby prey.
Do Mudpuppies Actually Bark?
The name “mudpuppy” comes from a popular but exaggerated idea that they sound like barking dogs. They are one of only a few salamanders that produce any vocalization at all, but the sound is more of a faint squeak than a bark. They’re also called “waterdogs” in parts of their range, reinforcing the canine connection. The squeaking likely happens when they’re handled or disturbed, not as regular communication.
How to Tell Them Apart From Lookalikes
Mudpuppies get confused with a few other animals, and the differences are worth knowing.
- Axolotls are the most common mix-up. Axolotls are also permanently gilled salamanders that never metamorphose, but they’re a completely different species native to Mexico. Axolotls are typically lighter in color (often white or pale pink in captivity) and have a broader, flatter head. Mudpuppies are rusty brown or gray with darker spots.
- Tiger salamander larvae look strikingly similar to mudpuppies, complete with external gills and an aquatic lifestyle. The key difference: tiger salamander larvae are temporary. They eventually lose their gills, develop lungs, and move onto land. A mudpuppy never will.
- Hellbenders are another large aquatic salamander found in some of the same regions, but they’re much bigger, growing up to three feet long. Hellbenders also lack external gills, relying instead on loose, wrinkly skin folds along their sides to absorb oxygen.
Are They Dangerous to Handle?
Mudpuppies are harmless. Like all amphibians, they have glands in their skin that produce mucus and mild secretions as a defense against bacteria and predators, but mudpuppies are not considered toxic to humans. They can bite if grabbed, though their teeth are small and the bite is unlikely to break skin. If you catch one while fishing, you can gently remove the hook and release it. The bigger concern runs the other direction: handling any amphibian with dry or dirty hands can damage their sensitive, permeable skin.
Maturity and Lifespan
Mudpuppies are slow to mature. They don’t reach reproductive age until around their sixth year, at a minimum length of about 8 inches. Females lay their eggs in late spring or early summer, attaching them individually to the underside of rocks or submerged logs. The female then guards the nest for one to two months until the eggs hatch. This slow reproductive pace means populations can take a long time to recover from declines.
Threats and Population Declines
Globally, mudpuppies are listed as “Least Concern” by the IUCN, and they have no federal protection in the United States. But that broad classification masks serious regional problems. Populations across the Great Lakes region have been declining, driven by a combination of habitat loss, pollution, invasive species, and one particularly unusual threat: chemicals used to control sea lampreys.
Sea lampreys are an invasive parasite devastating to Great Lakes fish, and wildlife agencies treat tributaries with a chemical lampricide to kill lamprey larvae. Mudpuppies, unfortunately, are highly vulnerable to the same chemical. In Vermont, a single treatment of the Lamoille River in 2009 killed an estimated 528 mudpuppies. When the river was treated again in 2013, fewer than 10 died, strongly suggesting the population had already crashed. Across Canada, an estimated 13,000 to 33,000 mudpuppies died between 2000 and 2019 from a combination of lampricide applications, botulism outbreaks, and extreme weather events. Young mudpuppies are especially susceptible, and repeated exposure appears to harm reproduction, making recovery even harder.
Several states and provinces have begun flagging mudpuppies as species of concern. Vermont lists them as declining in both abundance and distribution, and New York has proposed listing them as a species of special concern. The challenge is balancing lamprey control, which protects billions of dollars in Great Lakes fisheries, against the collateral damage to native species like the mudpuppy.