Amphibians of North Carolina
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Necturus maculosus - Mudpuppy

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Taxonomy
Class: Amphibia Order: Caudata Family: Proteidae
Taxonomic Comments: Necturus maculosus has the largest range of any Necturus species and two subspecies are currently recognized. These are the Common Mudpuppy (N. m. maculosus) that is found throughout most of the range of the species, and the Red River Mudpuppy (N. m. louisianensis) that is a disjunct southern form that is found in Arkansas and portions of surrounding states. A comprehensive analysis of genetic variation in this species has yet to be conducted, but Greenwald et al. (2020) used mtDNA to examine genetic variation in post-glacial regions in the northern portion of the range and documented an eastern and western cluster of populations that occur to the east or west of the Mississippi River. These probably reflect two groups that survived in a southern glacial refugium and expanded their ranges northward following the last glacial retreat. Chabarria et al. (2018) examined mtDNA variation in the N. beyeri complex, which is a group of Gulf Coast forms. They included a very small number of N. maculosus specimens in their analysis and found evidence of two genetic groups that were not concordant with those of Greenwald et al. (2020). These studies suggest that a taxonomic revision of N. maculosus may be needed, but a comprehensive survey of populations from throughout the entire range will be required before any changes are made.
Species Comments: The Mudpuppy has been used in numerous scientific studies in anatomy, developmental biology, and physiology and the results have many potential applications to human health.
Identification
Description: Necturus maculosus is a large, aquatic salamander with four toes on each hindlimb, a squared-off snout, and reddish bushy gills that are retained throughout life. The dorsal ground color varies from rusty brown to gray or grayish black and is overlain with scattered, bluish black spots. In rare instances the spots may be either absent or fused to form dorsolateral stripes (Petranka 1998). The venter is whitish to grayish and is sometimes spotted with bluish black spots. A dark bar is present on the head that extends from the snout through the eyes before terminating at the gills. The tail comprises about 30-35% of the total length and is keeled on the posterior half. Males in breeding condition have a swollen cloaca with two prominent papillae directed backwards. The female's cloaca is slit-like and often surrounded by a light-colored area. The adults range from 20-49 cm TL.

The hatchlings have prominent yolk sacs and are 14-15 mm SVL and 21-25 mm TL (Bishop 1941, Shoop 1965). A dark dorsal band extends down the midline of the back and is bordered on both sides by a light yellow stripe. A broad dark band also occurs below the yellow stripes along the sides of the body. Juveniles have the same general color pattern as hatchlings, but are more conspicuously marked with yellow and black stripes along the body. The juvenile pattern begins to approximate that of the adults after larvae exceed 13-15 cm TL (Bishop 1941).

Two subspecies are generally recognized by taxonomists. The Common Mudpuppy (N. m. maculosus) is found throughout most of the range of the species and has a rusty brown to gray dorsum with conspicuous bluish black spots, along with a gray venter that varies from being unspotted to heavily spotted. The Red River Mudpuppy (N. m. louisianensis) is a disjunct southern form that is found in Arkansas and portions of surrounding states. It has a light yellowish brown to tan dorsum. Many individuals show evidence of a dark dorsal stripe that is bordered on either side by a faint light stripe. The dorsum and sides of the belly are marked with large spots and blotches, but the center of the belly is light colored and immaculate (Petranka 1998). Some authorities treat the Red River Mudpuppy as a separate species (N. louisianensis). Detailed molecular studies from throughout the range of N. maculosus are needed to resolve the status of this southern disjunct.
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AmphibiaWeb Account
Distribution in North Carolina
Distribution Comments: The Mudpuppy inhabits a variety of permanently aquatic habitats in southern Canada and the eastern US. It occurs in Canada in southeastern Manitoba, southern Ontario, and southern Quebec. In the US, the range extends from Maine and other New England states westward through the Great Lakes region to Minnesota and the extreme eastern Dakotas, then southward from mostly west of the Eastern Continental Divide to northern Georgia, northern Alabama, northern Mississippi and north-central Louisiana. It reaches its southwestern limit in eastern Kansas and eastern Oklahoma. Populations in North Carolina are restricted to the major rivers and their larger tributaries in the western mountains.
Distribution Reference: Beane et al. (2010), Petranka (1998)
County Map: Clicking on a county returns the records for the species in that county.
GBIF Global Distribution
Key Habitat Requirements
Habitat: Necturus maculosus is a paedomorphic species that has gilled adults that are restricted to permanently aquatic habitats. Populations are commonly found in large streams and rivers with fast-flowing water and rocky substrates, as well as in clear, cool lakes at northern latitudes. They also occur in a variety of other habitats such as muddy canals and weed-choked bays, reservoirs, and sluggish, turbid streams in the southern portion of the range (Petranka 1998). Specimens reside beneath rocks, logs and other cover during the day and have been found as deep as 27 m below the surface of lakes. Populations in North Carolina occur in our larger rivers and their tributaries in the western mountains. Cool, clean, well-oxygenated streams with minimal sedimentation and rocky substrates provide ideal habitats for this species.
Biotic Relationships: Most of our freshwater mussel species have an early, parasitic larval stage that attaches to the gills or fins of a host fish. The larvae later metamorphose and the juvenile mussels drop off the fish and become free-living forms. Necturus maculosus is unusual in being the only known salamander host for a freshwater mussel, the Salamander Mussel (Simpsonaias ambigua).
See also Habitat Account for Montane Rocky Rivers
Life History and Autecology
Breeding and Courtship: Most of our knowledge about the breeding season is based on studies of northern populations where the adults mate primarily in the autumn, then sporadically through as late as April (Bishop 1941, Harris 1961, Petranka 1998). In Louisiana N. m. louisianensis breeds primarily during the winter months (Shoop 1965). Adults in New York often congregate in small groups beneath logs and rocks during the mating season, and females that mate in the autumn can retain sperm in their reproductive tracts for 6 months or more before ovipositing in late spring or early summer (Petranka 1998).

Detailed accounts of courtship are not available. Bishop (1926) gave an account of partial courtship in which the male swam and crawled over the tail or between the legs of a stationary female, but did not deposit a spermatophore. The spermatophore consists of a gelatinous base that supports a milky-white sperm mass and is 6-8 mm in diameter and 10-12 mm high (Petranka 1998). The extent to which males compete for females is not known, but most sex ratios are approximately 1:1 (Cagle 1954, Gibbons and Nelson 1968, Shoop 1965).
Reproductive Mode: The females typically nest beneath cover objects such as rocks and sunken logs and actively excavate depressions. They attach their eggs singly to the undersides of a support structure such as a rock in a monolayer that is typically 15-30 cm in diameter (Bishop 1926, Eycleshymer 1906, Petranka 1998, Smith 1911). Each egg is attached by a disc-like expansion of the outer envelope and has a short stalk. Freshly laid eggs are cream to light yellow, 5-6.5 mm in diameter, and are surrounded by three jelly envelopes (Petranka 1998). Nests that Bishop (1941) observed in New York streams were constructed beneath rocks at depths of 10-60 cm. They were commonly found just below riffles in moderately flowing water, and the entrances to the cavities faced downstream.

Females in northern populations usually begin ovipositing in late April through early June, while those in Louisiana oviposit in May (Petranka 1998, Shoop 1965b). Females remain with their eggs through hatching and presumably defend them from predators. The length of the embryonic stage varies depending on prevailing water temperatures, but the eggs typically require 6-9 weeks to reach the hatching stages (Bishop 1941, Petranka 1998, Smith 1911).

Estimates of clutch size based on counts of eggs in nests are generally lower than those based on dissections of gravid females. This may in part reflect predation as well as cannibalism by large adults (Petranka 1998). Fitch (1959) reported a mean of 60 eggs (range = 28-101) in 11 Michigan nests, but three gravid females from the same population contained 105-140 ova. Other nest records include three Pennsylvania nests with 87-140 eggs, five Wisconsin nests with 18-87 eggs (mean = 66; Smith 1911), and a nest in Wisconsin with 62 eggs (Eycleshymer 1906, Petranka 1998). Shoop (1965) found an average of 54 mature ova in N. m. louisianensis from Louisiana (range = 32- 91), while Trauth et al. (1990) found an average of 106 ova (range = 48-174) in Arkansas specimens.
Aquatic Life History: Most aspects of the natural history of juveniles are poorly documented. The hatchlings and juveniles show a tendency to prefer microhabitats with relatively low to moderate current. They have been found in leaf litter and in the deeper, quieter waters of large streams, and in vegetated shallows on the edges of lakes and rivers. However, they also are occasionally taken in riffles (Bishop 1941, Petranka 1998, Pfingsten and White 1989). Hatchlings studied by Bishop (1926) reached an average of 56 mm TL when 13-months old. One year olds grew an average of 26-39 mm TL per year and averaged about 187 mm TL when 5-years old. Sexual maturity was reached shortly thereafter when individuals exceed 200 mm TL. Male and females studied by Shoop (1965) become sexually mature at 130-137 mm SVL and 127-157 mm SVL, respectively (Petranka 1998). The adults are long-lived. Canadian specimens have often been found that are over 20 years old, and one was aged as being 34 years old (Gendron 1999). However, the great majority appear to live < 20 years (e.g., McDaniel et al. 2009).

The juveniles and adults hide in burrows in stream banks or beneath rocks, logs, or flood debris during the day, but emerge at night and crawl slowly over the bottom in search of prey. Individuals appear to be opportunistic, gape-limited predators and consume a wide variety of prey that ranges from tiny crustaceans to small fishes. Numerous dietary studies have been conducted that were reviewed by Harris (1959), Petranka (1998) and Gendron (1999). The hatchlings and young larvae consume small prey such as small crustaceans, midge larvae, mayflies, and aquatic mites, while the larger juveniles and adults consume a much larger size range of prey. Invertebrates that are consumed include numerous taxa of aquatic insects, along with amphipods, crayfishes, snails and other mollusks, and earthworms. Larger individuals will take vertebrates. The known vertebrate prey include over 15 species of fishes, five species of salamanders, tadpoles, and a turtle. Fishes can be very important prey in the winter diets of northern populations (Gendron 1999). Large adults will also often eat the eggs and smaller larvae of conspecifics and feed on the eggs of fishes.

Adults in both northern and southern populations are generally most active during the cooler months of the year based on trapping records and catches by fishermen. Individuals in a southern Michigan lake migrate to shoreline areas in the spring, then retreat to deeper waters during the summer (Gibbons and Nelson 1968). Populations in rivers tend to have relatively small home ranges and do not move long distances between recaptures. Chellman et al. (2017) reported that mudpuppies in a Vermont stream moved an average of 82 meters between captures (range = 60.5–103.1 meters), and that males tended to move longer distances on average than females. The maximum distance moved was 780 m for a male and 440 m for a female, and the largest movements (> 150 m) were in an upstream direction during early spring. These values are similar to those reported by Shoop and Gunning (1967) where adults in a Louisiana stream moved an average of 81 m between captures.
General Ecology
Adverse Environmental Impacts
Habitat Loss: Necturus maculosus was once a very common species throughout the Great Lakes region and elsewhere. Healthy populations with high densities of mudpuppies still occur in the region (Gendron 1999), but many populations appear to be in decline (Craig et al., 2015, Gendron 1999, Pfingsten and White 1989). Factors that have contributed to declines include the use of lampricides to control the sea lamprey (Matson 2005), habitat degradation and loss, stream sedimentation, inputs of toxins and excessive nutrients, and the alteration of aquatic communities by invasive species (Gendron 1999, Holman 2012).
Habitat Fragmentation: Populations have become fragmented in many areas due to the construction of reservoirs. Mudpuppies often thrive in cold lakes in Canada and the northern US, but appear to fair poorly in warmer reservoirs in the southern portion of the range.
Interactions with Humans: Mudpuppy populations have been directly affected by humans due to unsustainable and unregulated commercial harvesting for research and for use in teaching labs. Bishop (1926) recalls a catch of about 2,000 mudpuppies in one haul of a commercial seine in Michigan. Fisherman take countless thousands on baited hooks during the winter and spring as incidental catch. They will often kill mudpuppies that are caught because of the erroneous belief they are poisonous, or that they excessively consume game fish and fish eggs (Ruthven et al. 1912, Bishop 1941, Petranka 1998).
Status in North Carolina
NHP State Rank: S2
Global Rank: G5
Status in North Carolina: SC
Environmental Threats: Excessive sedimentation of streams associated with urbanization and agricultural activities may be the greatest threat to this species in North Carolina. Excessive sedimentation can eliminate surface cover and nesting sites and reduce food resources for the larvae and adults.
Status Comments: We know very little about the status or most aspects of the life history of N. maculosus in North Carolina. Very small numbers of specimens have been collected over the years, which suggests that population densities are very low in many areas where extant populations are known to exist.