Necturus maculosus (Rafinesque, 1818)
Basis for Listing
The Mudpuppy (Necturus maculosus) is widely distributed across the eastern half of the United States and Canada. In Minnesota, this fully aquatic salamander is found in medium to large rivers and larger lakes within the Mississippi, Minnesota, Red, and St. Croix river basins. This species is common in portions of the Minnesota and St. Croix river basins. It is relatively common in the Mississippi River main stem from St. Anthony to Red Wing but apparently less common in the Mississippi River and its tributaries south of Red Wing. It is uncommon in rivers in the Red River basin but relatively abundant in some of the lakes occurring in the southeastern portion of the basin. Although a historic record exists from Lake Superior, there are no other records from the Lake Superior watershed in Minnesota, though suitable habitat is present. Until recently, this species has received little attention in Minnesota; therefore information regarding its distribution and abundance are subject to change. Since the Mudpuppy is a possible bioindicator of water quality and aquatic health, there is a need for additional informationon on this species. Threats to Mudpuppy populations in Minnesota include habitat loss, siltation, pollution, exploitation by humans, and the use of lampricide. This species is the only known larval host for the endangered Salamander Mussel (Simpsonaias ambigua); therefore local extirpation of Mudpuppies would ultimately result in the loss of this rare species. Due to the lack of data on its current distribution and abundance within the state, as well as the threats listed above, the Mudpuppy was designated a species of special concern in 2013.
The Mudpuppy is Minnesota’s only fully aquatic salamander and is easily recognizable by its permanent dark red bushy gills. Adults are brown, reddish brown, or gray above, with scattered dark blotches and spots with indistinct borders; the number and size of these dark markings is variable. The underside is white to gray. The tail is short and laterally compressed, giving it a paddle-like appearance. Both the front and hind feet have four toes. Larvae and juveniles have a distinct yellow stripe down each side of the back. Adults may grow to 48 cm (19 in.) in total length, making it Minnesota’s largest salamander species.
This salamander is entirely aquatic. Throughout its range it inhabits rivers, lakes, reservoirs, and sluggish streams (Petranka 1998). In southern Minnesota, this species prefers large and medium rivers; while north of the Minnesota River, this salamander inhabits large lakes. Typically, rocky structures and substrates are utilized in all aquatic environments, but some are also found in muddy substrates with occasional rocks or logs for refuge and nesting.
Biology / Life History
Mudpuppies are active year round. Courtship and mating typically take place in the fall; after which time adults congregate in shallow water, where they remain until the following spring. A second wave of courtship and mating may occur in February or April (Petranka 1998). Either way, fertilization is delayed until spring. Nests are constructed in May under submerged structures, such as rocks, logs, or boards. An average of 60 eggs are laid singly, attached to the underside of the structures. Nests are guarded by females during the incubation period, which lasts 38-63 days, depending on water temperature. Hatchlings may remain with the mother for a short time after emerging from their eggs. Maturation occurs after five years (Vogt 1981). Adults move to deeper water during the summer, while juveniles may remain in shallow water in vegetation near shore or in riffles (Pfingsten and Downs 1989). Most activity is nocturnal, though it may also occur during the day in deep water; the species has been recorded at depths of 28 m (92 ft.; Hacker 1957). Territoriality has not been observed. Predators include predatory fish, birds, mammals, snakes, other Mudpuppies, and humans. Mudpuppies may remain hidden under rocks or other structures to avoid predation. When encountered in the open, they may rapidly swim away. When restrained, this species may bite, but it produces no poison or venom. Restraint may be extremely difficult due to the intense amount of slime on the skin. Captive longevity may reach >30 years (Bonin et al. 1995). This species feeds primarily on crayfish and aquatic insects, though it will also consume other small crustaceans, small fish, earthworms, and salamanders, including other Mudpuppies and their eggs (Petranka 1998).
Conservation / Management
Threats to the Mudpuppy include loss and alteration of habitat, degradation of water quality, pollution, siltation, and lampricide use. While Mudpuppies are apparently tolerant of some siltation, habitat modification activities such as river channelization, dams, shoreline development, and dredging can bury rocks, logs, or other types of cover necessary for refuge and nesting. Dams restrict migration, impacting genetic diversity. This species is also harvested in large numbers in western Minnesota for biological supply companies. They are also collected for the pet trade and for bait. During cold months, anglers can capture Mudpuppies while fishing; they sometimes kill them because they believe them to be poisonous or venomous. An additional threat is the lampricide TFM (3-trifluoromethyl-4-nitrophenol), used to control the invasive Sea Lamprey (Petromyzon marinus) in Lake Superior. A study conducted in Ohio found that Mudpuppy populations decreased by 29% the year following TRM application (Matson 1990). Many of these human-caused threats need to be managed and regulated. Improving water quality, reducing siltation, and preserving submerged natural structures would benefit this species. Recent Mudpuppy die-offs have been documented in Minnesota, the exact cause of which is unknown. Additional investigation is needed to determine the cause and prevention of these events. Continuing surveys to assess Mudpuppy distribution and abundance throughout the state would lead to a better understanding of conservation and management needs.
Conservation Efforts in Minnesota
In 2010, a statewide survey was initiated in five major watershed basins to assess the current distribution and status of N. maculosus in Minnesota. Specimens were captured in all five basins, and Mudpuppies were found to be common in the Minnesota, St. Croix, and southeast tip of the upper Mississippi river drainages. It was uncommonly captured in the Red and lower Mississippi river drainages. These survey results will help guide conservation and management actions for this species.
Jeffrey B. LeClere (MNDNR), 2018
(Note: all content ©MNDNR)