Physical Description - This is a large, permanently-gilled salamander. It has four toes each on both hindlimb. The gills are dark red. The dorsum is rusty brown to gray with black blotches. The venter is white to gray and sometimes spotted. Extending through the eyes and to the gills is a dark bar. Its snout is heavily truncated. Juveniles begin to look like adults at 13-15 cm. Hatchlings have prominent yolk sacs with a dark dorsal band with a light yellow stripe.

Historical versus Current Distribution - Mudpuppies (Necturus maculosus) were historically distributed throughout eastern and middle North America (Eycleshymer, 1906). The distribution was further defined by Stejneger and Barber (1923) to include tributaries of the Great Lakes, the Mississippi and Hudson River systems, Lake Champlain, and rivers of Alabama, Georgia, and North and South Carolina. Two subspecies are recognized. The nominate form, Necturus m. maculosus (Rafinesque, 1818; Collins, 1990), occupies a broad distributional range extending from southern Québec, Lake Champlain, and eastern New York state, westward across southern Ontario to southeastern Manitoba and eastern Kansas, and south to northern Mississippi, Alabama, and Georgia. They are absent from the Adirondack Mountains, northern and far southern Minnesota, all but eastern Iowa, and parts of Missouri and Tennessee. Red River Mudpuppies (Necturus maculosus louisianensis; Viosca, 1937; Collins, 1990) occur from southern Missouri into south-central Kansas through eastern Oklahoma and Arkansas into northern Louisiana (Conant and Collins, 1991).

Historical versus Current Abundance - Few quantitative data are available. Mudpuppies were reported as abundant in the Great Lakes region (Eycleshymer, 1906; Pearse, 1921). For example, Milner (1874) cited a fisherman at Evanston, Illinois, who set 900 hooks and caught 500 Mudpuppies in one night. Pearse (1921) credited Alexander Nielsen of Venice, Ohio, as taking large numbers of Mudpuppies for years from Sandusky Bay of southern Lake Erie. Bishop (1941b) recorded Mudpuppies as common in the St. Lawrence, Hudson, and Mohawk rivers and as abundant in several of the Finger Lakes of New York. Vogt (1981) relates that Mudpuppies formerly were caught by the hundreds in Lake Mendota, Wisconsin. The current status of Mudpuppies is unknown in many areas. They are reported to have declined in Lake Erie (Pfingsten and White, 1989), in Iowa (Lannoo, 1994), and in parts of the Great Lakes region (Harding, 1997).

Breeding - Reproduction is aquatic.

Breeding migrations - Definite breeding migrations are unknown. In the autumn, males occupying both stream and lake habitats search for females within their shallow water retreats. Several males and females may share a communal retreat throughout the breeding season (Bishop, 1941b). Although most mating is believed to occur during the autumn, Bishop (1941b) located a male in reproductive condition beneath a rock slab with three females on 18 April, and occurrences of multiple males and females beneath the same slab become commonplace in August in northeastern Ohio (personal observations).

Breeding habitat - Fall breeding activities take place in the shallow waters of lakes and streams at depths ranging from only decimeters to several meters, where retreats beneath rock slabs, logs, or planks occur. Sperm are stored in spermatheca over winter (Harris, 1959c). Ovulation followed by delayed fertilization and spawning occur in the spring, from April–June; timing is dependent upon water temperature. Locally, most females spawn within a 2–3 wk period (Bishop, 1926; Smith, 1911b).

Egg deposition sites - Oviposition occurs on the roof of an excavated nesting cavern (Smith, 1911b; Bishop, 1926).

Clutch size - Clutch size in Mudpuppies was found to average 66 at Lake Monona, Wisconsin, in lake habitat (Smith, 1911b); 85 in New York (Bishop, 1941b); and 83 at northeastern Ohio in stream habitats (Matson, 1998). Clutch size for Red River Mudpuppies was 36 in Big Creek, Louisiana (Shoop, 1965b). The ova measure 5–6 mm in diameter and are yellow spheres containing much yolk. While pendant from a pedicel in the nest chamber, three membranes encompass each egg increasing its width to 11 mm and its length to 14–16 mm. The period of incubation for the developing clutch extends from 38–63 d and is water temperature dependent (Bishop, 1941b).

Altig & McDiarmid 2015 - Classification and Description:

Larvae/Metamorphosis - Larval Mudpuppies average 22.5 mm TL at hatching (Bishop, 1941b). Most hatchlings remain in the nest cavity at least 6–8 wk until the large yolk sac has been absorbed. By the end of August, most hatchlings have left the brood site and have found retreats beneath objects in the stream channel (personal observations).

Juvenile Habitat - Larvae in their first winter or spring and juveniles through ages 3–4 yr are found in greater numbers in the substrate of pools where silt and organic debris have accumulated to a minimum thickness of several cm (Matson, 1990). Later in spring, many juveniles are found in portions of the stream lacking organic detritus, beneath retreats not occupied by adults or predatory fishes such as stonecats (Noturus flavus; Matson, 1990; personal observations). Cagle (1954) collected larvae during February in shallow holes where organic detritus had accumulated to many cm, and Bishop (1941b) reported that juveniles take up residence in deeper holes. Juvenile Mudpuppies have been observed in riffle areas (Pfingsten and White, 1989).

Adult Habitat - Mudpuppies are found in both clear and silted waters of lakes, reservoirs, canals, ditches, and streams in the presence or absence of aquatic plants. Large populations may be present where retreats, such as flat rock slabs, logs, and planks are numerous. Lentic streams with mud substrates, crayfish burrows, undercut banks, and tree roots provide suitable habitat. Adults prefer well-aerated water downstream or to the sides of riffles (Bishop, 1941b). Streams or sections of streams coursing over exposed bedrock and providing apparently suitable rock slabs or other retreats will support few Mudpuppies if a mud or mud-detritus substrate is absent from beneath the objects (personal observations). Mudpuppies have been reported from depths to 17 m in Lake Erie by White (Pfingsten and White, 1989) and to 27 m in Green Bay, Lake Michigan, by Reigle (1967).

Home Range Size - The summer activity ranges of adult Mudpuppies in the Grand River of northeastern Ohio averaged 136.1 m2 (Matson, 1998). No other reports of home range size are available. Both Shoop and Gunning (1967) and Matson (1998) cite evidence for long-term site fidelity.

Territories - Unknown.

Aestivation/Avoiding Dessication - Active all year (Eycleshymer, 1906; Bishop, 1941b; Shoop and Gunning, 1967).

Seasonal Migrations - Vernal movements in lakes from deep water toward the shore were reported by Milner (1874), and Pearse (1921), Gibbons (1968); Pope (1947) reported annual migrations up tributaries to Lake Michigan in the Chicago area. Pope (1947) did not report any associated mortality. Gibbons and Nelson (1968) stated that these migrations did not appear to be related to reproduction because a 1:1 sex ratio was observed, mating occurs in fall or winter, and the movement included juveniles. Late mid-March movements in the Mud River and Twelvepole River were reported in West Virginia (Green and Pauley, 1987).

Torpor (Hibernation) - Active all year (Eycleshymer, 1906; Evermann, 1920; Bishop, 1941b).

Interspecific Associations/Exclusions - Only known host for salamander mussels (Simpsonaias ambigua).

Age/Size at Reproductive Maturity - Age at first reproduction was reported as 5–6 yr at about 200 mm TL (Bishop, 1941b) and 7–8 yr at 175–200 mm TL (Pope, 1947).

Longevity - At least 29 yr (Bonin et al., 1995). Recently, a male has been aged at 34 yr (Gendron, 2003).

Feeding Behavior - Prey include scuds (Gammarus sp.), sculpins (Cottus sp.; Bishop, 1941b), crayfish, small fish, fish eggs, numerous aquatic insects including adults and their larvae or nymphs, ostracods, amphipods, plant material in excess of what would be ingested by accident (Pearse, 1921), annelids, small salamanders (Eurycea sp., Desmognathus sp., Notophthalmus sp.; Bishop, 1941b), tadpoles (Harris, 1959b), and eggs of Hellbenders (Cryptobranchus alleganiensis; Abbott, 1934). Evermann (1920) reported Mudpuppies feeding upon small fish including brook silversides (Labidesthes sicculus), river shiners (Notropis blennius), and banded killifish (Fundulus diaphanus). Mudpuppies will also ingest lamprey ammocetes present in the water column during sea lampricide treatments (personal observations; J. Reblin, unpublished data). Cannibalism is not uncommon (Bishop, 1941b). Mudpuppies are primarily nocturnal but may be active diurnally in clouded, silted, or heavily vegetated waters (Bishop, 1926). Mudpuppies forage nocturnally in shallow waters affording little cover and do so more extensively during the colder months from December–April (Shoop and Gunning, 1967). Increased winter foraging activity may be a behavioral change due to reduced activity and feeding by predatory fishes.

Predators - Known predators of Mudpuppies include predatory fishes, hellbenders, water snakes (Colubridae), herons, otters (Harris, 1959b), larger Mudpuppies (Bishop, 1941b), and crayfish; fish prey upon eggs and hatchlings flushed from the nest cavity (personal observations).

Anti-Predator Mechanisms - Primarily nocturnal. Cryptic coloration (Bishop, 1941b). Mudpuppies have a lateral line system consisting of pressure, motion, and electroreceptor sensory cells triggering fast escape (Duellman and Trueb, 1986). Escapes are accomplished through C-starts—a rapid fishlike swimming accomplished by folding legs against the flanks and vigorously lashing the laterally compressed tail (Harris, 1959a).

Diseases - Saprolegnia, water mold (Bishop, 1926).

Parasites - Sphyranura osleri, trematode attached to the gills and skin (Bishop, 1941b; Harris, 1959a); Ophiotaenia lonnbergii, a proteocephalid of the intestine; Simpsonaias ambigua, salamander mussel that attaches to the gills (Pearse, 1921).

Conservation - Mudpuppies have a broad geographical range, and their survival over the short term is probably secure, but their status over much of their range is poorly understood. Chemical water pollutants and heavy siltation have reduced habitat quality in many regions and have contributed to declines in population size. Agricultural, industrial, and residential practices targeted toward the reduction of pollution and siltation will aid in the conservation of this species. Less reliance upon the lampricide TFM in the Great Lakes and some eastern states for control of sea lampreys (Petromyzon marinus) would allow chemically depressed populations to recover and approach carrying capacity (see Matson, 1998). Education must overcome the ignorance and misunderstanding regarding the existence and niche of Mudpuppies. Erroneous information remains pervasive among biologists, fishers, and others who continue to persecute Mudpuppies; consequently, Mudpuppies are often used for fish bait, or commonly, hooked animals are discarded to die on the ground or on the ice.

Mudpuppies are considered Endangered/Extirpated by Maryland, Threatened in Iowa, and a Species of Special Concern in Indiana and North Carolina.

• Altig, Ronald & McDiarmid, Roy W. 2015. Handbook of Larval Amphibians of the United States and Canada. Cornell University Press, Ithaca, NY. 341 pages.
• AmphibiaWeb. 2020. University of California, Berkeley, CA, USA.
• Conant, R., 1975, A field guide to reptiles and amphibians of Eastern and Central North America, 429 pgs., Houghton Mifflin Co., Boston, MA
• Bishop, S.C., 1943, Handbook of Salamanders, 555 pgs., Comstock Publ. Co., New York, NY
• Petranka, J.W., 1998, Salamanders of the United States and Canada, 587 pp. pgs., Smithsonian Institution Press, Washington, DC