The mudpuppy is an amphibian that spends its entire life in the aquatic environments of North America. Found across a vast range from southern Canada down to Georgia, this large salamander is frequently mistaken for an eel, a lizard, or even a fish. It is a harmless resident and true aquatic specialist of freshwater systems, including rivers, lakes, and streams.
An Aquatic Salamander That Never Grows Up
The mudpuppy belongs to the genus Necturus, a group of salamanders defined by their permanent aquatic existence. Its most striking biological feature is neoteny, sometimes referred to as paedomorphosis. This means the adult animal retains physical characteristics typically only found in the larval or juvenile stage of other salamanders. It keeps its external gills throughout its entire lifespan, which can extend for over a decade in the wild. While most salamanders lose their gills and develop lungs for air-breathing, the mudpuppy relies on its external gills for its primary means of gas exchange in the water.
Distinctive Physical Features
The mudpuppy is a relatively large salamander, with adults typically measuring between 8 and 13 inches in total length, though some specimens can reach up to 19 inches. Its body is robust, and its head is broad and flat, featuring very small eyes and a blunt snout. The tail is laterally compressed, meaning it is flattened from side to side, which helps propel the animal through the water like a paddle.
The most notable physical feature is the set of bright red or maroon external gills that flare out prominently from the sides of its neck. These feathery, plume-like structures are rich in blood vessels, providing the surface area necessary to extract oxygen from the water. Mudpuppies living in cold, highly oxygenated water tend to have shorter gills, while those in warmer, oxygen-poor water develop longer, bushier gills to maximize absorption. The skin is smooth, lacks scales, and often has a slimy texture.
The mudpuppy possesses four well-developed, short limbs, each ending in four toes. This four-toe count on the hind feet is a distinguishing feature that helps differentiate the mudpuppy from other salamanders that might have five toes. Despite their small eyes, they have sensory organs in their skin that allow them to detect changes in water pressure and movement.
Habitat, Diet, and Behavior
Mudpuppies are found exclusively in permanent freshwater bodies across eastern North America, inhabiting rivers, lakes, streams, and reservoirs. They prefer areas with ample cover on the bottom, often hiding under rocks, submerged logs, or dense aquatic vegetation during the day. They have been documented living in waters as deep as 100 feet.
The species is primarily nocturnal, active at night when it leaves its shelter to forage along the bottom. In murky or weedy water, however, the mudpuppy may be active throughout the day. It remains active year-round, even under the ice of frozen lakes during the winter months.
The mudpuppy is an opportunistic carnivore, using a “suck and gape” method to capture prey. Its diet consists mainly of small aquatic organisms, including crayfish, insects and their larvae, small fish, fish eggs, and aquatic worms. Using its sense of smell and its sensitivity to water movement, the mudpuppy effectively hunts in low-light conditions.
The Origin of the Name Mudpuppy
The common name “mudpuppy” is rooted in a popular misconception about the animal’s behavior. The name likely originated from the mistaken belief that the salamander makes a sound resembling a dog’s bark. When pulled from the water, a mudpuppy may expel air from its gill slits or lungs, sometimes resulting in a soft, squeaking, or grunting sound. The mudpuppy does not actually bark like a mammal; the sound is simply a reflex related to breathing or distress. This species is also widely known by the alternate common name “waterdog,” especially in the southern parts of its range.