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The massasauga (Sistrurus catenatus) is a venomous pitviper rattlesnake species found primarily in the United States. Three subspecies are currently recognized including the nominate subspecies described here.
The adults are not large, ranging from 45 to 75 cm (18 to 30 in) in length. The color pattern consists of a grey or tan ground color with a row of large rounded brown/black blotches or spots down the center of the back and three smaller rows of alternating spots down each side. Solid black melanistic examples are also known, as well as cases where the back blotches join with those on the sides. Young massasauga are well-patterned but paler than the adults. This is the only Ontario snake with vertical pupils. It has heat-sensing pits on each side of its smallish head, the scales are keeled and the anal scale is single.
Massasauga, massasauga rattlesnake, massasauga rattler (Ontario), black massasauga, black rattler, black snapper, gray rattlesnake (Iowa), little grey rattlesnake (Canada), muck rattler, prairie rattlesnake, spotted rattler, swamp rattler, víbora de cascabel (Mexico), dwarf prairie rattlesnake, eastern massasauga great adder, ground rattlesnake, Kirtland's rattlesnake, little black rattlesnake, Michigan point rattler (Michigan), prairie massasauga, rattlesnake, small prairie rattlesnake, snapper, swamp massasauga, swamp rattlesnake, and triple-spotted rattlesnake.
Found in North America from Ontario (Canada) and western New York State southwest to southeastern Arizona and northern Tamaulipas, Mexico. In Mexico, isolated populations exist in southern Nuevo León, north-central Coahuila and in Samalayuca, Chihuahua. It occurs in various habitats ranging from swamps and marshes to grasslands, usually below 1500 m elevation. The type locality given is "... on the prairies of the upper Missouri" (Valley, USA).
|This section possibly contains original research. (November 2009)|
This species is classified as Least Concern (LC) on the IUCN Red List of Threatened Species (v3.1, 2001). Species are listed as such due to their wide distribution, presumed large population, or because it is unlikely to be declining fast enough to qualify for listing in a more threatened category. The population trend is unknown. Year assessed: 2007.
In Indiana and Ohio, the massasauga is listed as an endangered species and Illinois may soon follow. It is also listed in Michigan as Special Concern and as a candidate for federal listing. However, it does not have any designation on the U.S. federal Endangered Species Act. The two subspecies found in the drier areas of the southwestern United States and northern Mexico are also considered endangered or at risk by some[who?] state governments.
The Massasauga Rattlesnake is listed as threatened under Ontario's Endangered Species Act, 2007, and is protected under the Fish and Wildlife Conservation Act.  It is found only near the eastern shore of Georgian Bay, the Bruce Peninsula, the North Shore of Lake Huron, Wainfleet Bog, and Ojibway Prairie. It is becoming rare in Canada due to persecution and loss of habitat and is designated as Threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), as well as the Committee on the Status of Species-at-Risk in Ontario (COSSARO).
In Pennsylvania, the species has experienced a rapid decline, largely because of habitat loss. Historically this has been due to human activity, and more recently primarily from natural forest succession. By 1988, the snake had disappeared from half of the counties that constituted its historical range. A 2003-2005 survey showed only four locations in two counties with confirmed populations. It is classified as critically imperiled to imperiled in the commonwealth.
The diet consists of a variety of small vertebrates, including mammals, lizards, and other snakes, as well as invertebrates such as centipedes. Mammals and reptiles make up their bulk of their diet. Adults feed mainly on rodents, while juveniles usually prey on reptiles: more often lizards in western populations and snakes in eastern ones. Frogs also constitute an important part of their diet: Ruthven (1928) mentioned that in Michigan they made up the main portion of their diet. According to Klauber (1956), S. catenatus feeds on frogs more frequently than any other rattlesnake. In general, however, frogs are not an important part of the diet, although this does seem to be more typical in certain northern and eastern populations.
The venom of rattlesnakes contains specialized digestive enzymes that disrupt blood flow and prevent blood clotting. Severe internal bleeding causes the death of the small animals that this snake eats. After envenomation, the rattlesnake is able to withdraw from the dangers of sharp toothed prey animals until they are subdued and even partially digested by the action of the venom.
S. c. catenatus is rather shy and avoids humans when it can. Most massasauga snakebites in Ontario have occurred after people deliberately handled or accidentally stepped on one of these animals. Both of these scenarios are preventable by avoiding hiking through areas of low visibility (in rattlesnake country) when not wearing shoes and long pants, and by leaving the massasaugas alone when they are found. There are only two recorded incidents of people dying from massasauga rattlesnake bites in Ontario and in both cases they did not receive proper treatment. Recent studies indicate that Ontario Hospitals in rattlesnake country often do not have anti-venom, as Massasauga specific anti-venom is not easy to come by. http://metronews.ca/health/3715/anti-venom-crisis-in-ontario/
|Subspecies||Taxon author||Common name||Geographic range|
|Sistrurus catenatus (S. catenatus)||(Rafinesque, 1818)||eastern massasauga||United States: central and western New York south of Lake Ontario, western Pennsylvania, northern and central Ohio, northern Indiana, lower Michigan, Illinois, southern and southwestern Wisconsin, extreme southeastern Minnesota, eastern Iowa, and northeastern Missouri|
Canada: southern Ontario along the shores of Georgian Bay, Lake Huron, and Lake Erie
Considered to be its own separate species as of 2011.
|Sistrurus tergeminus edwardsii (S. t. edwardsii)||(Baird & Girard, 1853)||desert massasauga||United States: extreme southeastern Arizona; central and southern New Mexico; western Texas about as far north and east as the Colorado River; the Rio Grande Valley; and throughout the Texas Gulf Coast region extending as far north as Brazoria County as well as on several barrier islands including North Padre Island, Matagorda Island, and San José Island|
Mexico: isolated populations in the country's northeast region bordering Texas
|Sistrurus tergeminus (S. tergeminus)||(Say, 1823)||western massasauga||United States: extreme southeastern Nebraska and northwestern Missouri, east-central Kansas, west-central Oklahoma, and northern and central Texas about as far southwest as the Colorado River|
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