Sistrurus catenatus (Rafinesque, 1818)
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Sistrurus catenatus catenatus
Basis for Listing
The eastern massasauga (Sistrurus catenatus catenatus), one of three subspecies of massasauga, occurs in the upper Midwest and southern Ontario. Its occurrence in Minnesota is based on a few reliable sightings in the southeast part of the state, and one specimen whose collection location is questionable. At present, there is no evidence of established breeding populations on the Minnesota side of the Mississippi River (hence the blank range map). However, populations remain extant on the Wisconsin side of the river.
The massasauga is one of Minnesota's two venomous snakes. It is of medium size, averaging 47-76 cm (18.5-30 in.) long. The massasauga has a grayish-brown background overlaid by a pattern of dark brown blotches with 2 or 3 rows of smaller spots along each side. The tail is ringed, with bands the same color as the dorsal spots, and ends in a segmented rattle. Its small size and spotted body pattern distinguish it from the timber rattlesnake (Crotalus horridus), which is larger (80-122 cm (31.5-48 in.) long) and has a more banded body pattern.
Massasaugas prefer wet habitats such as marshes, bogs, and swamps, but they also use old fields, woods, and pastures, especially during the summer. Two necessary habitat components are areas of mixed sun and shade for thermoregulation, and mammal burrows, tree stumps, or rock crevices for overwintering.
Biology / Life History
Massasaugas overwinter in mammal burrows, crayfish burrows, tree stumps, or rock crevices from mid-October until late April (Vogt 1981; Oldfield and Moriarty 1994). They spend the spring in meadows and wetlands, basking in sunny spots within a home range of about 1 ha (2.5 ac.). During the summer, most snakes move to upland fields and meadows, and become active mainly at night. Gravid females appear to move less and bask more than males and non-gravid females, apparently to shorten gestation (Johnson et al. 2000). Breeding occurs in the fall, and the following summer females give birth to 3-20 fully formed young. The young remain with their mother for about a week, shed their skins for the first time, and then disperse. Females are not thought to become reproductively mature until at least their third year, and there is some evidence that they breed only every other year (Reinert 1981). Massasaugas eat mainly small rodents, but frogs are a major food source for juveniles (Seigel 1986). Massasaugas are ambush predators that wait for prey to wander by, then bite it and inject it with venom. They swallow their prey whole after it has died. Massasaugas are shy and secretive, and will strike at humans only if they feel threatened and cornered (Oldfield and Moriarty 1994).
Conservation / Management
A major aspect of any massasauga management program is the enforcement of regulations to protect snakes from collection and willful destruction. Minimizing loss or degradation of their habitats to agriculture, dredging, and stream channelization is also an important aspect of massasauga management. In this regard, bottomland habitat along the Mississippi River could be protected, particularly in Goodhue, Wabasha, Winona, and Houston counties where massasaugas may exist. Massasaugas depend on natural disturbances to maintain open areas in their habitat. Recent research indicates that maintaining open areas through cutting, burning, or the use of herbicide is important to this species. Fire can also be used to maintain open fields adjacent to bottomlands, but burning should be conducted in early spring before snakes emerge from hibernation (Johnson et al. 2000). General prescribed burning guidelines have been developed for amphibians and reptiles in the Midwest, although land managers conducting burns in areas with known rare reptile or amphibian species or high concentrations of reptiles and/or amphibians may wish to contact their Regional Nongame Wildlife Specialist for input on burn planning, including timing of burns, so as to minimize impacts on these species.
Conservation Efforts in Minnesota
The Minnesota Biological Survey conducted surveys for massasaugas in Houston, Wabasha, and Winona counties in 1993. Twenty-three search areas were identified as having suitable habitat for this species, but no massasaugas were found. Additional surveys funded by the Minnesota DNR in 2002 and 2003 also found no massasaugas (Naber 2004).