Sistrurus catenatus

Sistrurus catenatus

Common names: massasauga, black massasauga, black rattler, more.
Sistrurus catenatus is a venomous pitviper species found primarily in the United States. Three subspecies are currently recognized, including the nominate subspecies described here.

Description

Adults are not large, ranging from 45 to 75 cm in length. Its color pattern consists of a grey or tan groundcolor with a row of large rounded brown/black blotches or spots down the centre 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. A rattle is present on the tail. Young massasauga rattlesnakes 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.

Common names

Massasauga, black massasauga, black rattler, black snapper, gray rattlesnake (Iowa, fide Guthrie, 1927), little gray rattlesnake (Canada), muck rattler, prairie rattlesnake, pygmy rattler, sauger, spotted rattler, swamp rattler, víbora de cascabel (Mexico), dwarf prairie rattlesnake, eastern massasauga, great adder, ground rattlesnake, Kirtland's rattlesnake, little black rattlesnake (Barton, 1805), massasauga rattlesnake, massasauger, prairie massasauga, rattlesnake, small prairie rattlesnake, snapper, swamp massasauga, swamp rattlesnake, triple-spotted rattlesnake, mississauga.

This is the only venomous snake in Michigan, where it is known as the Michigan rattler.

The name massasauga means "great river-mouth" in the Chippewa language and was probably given to describe its habitat in Chippewa country: swampland surrounding river deltas.

Geographic range

Found in North America from southeastern Ontario (Canada) and western New York State southwest to southeastern Arizona (USA) and northern Tamaulipas (Mexico). In Mexico, isolated population exist in southern Nuevo León and north-central Coahuila. It occurs in various habitats ranging from swamps and marshes to grasslands, usually below 1500 m altitude. The type locality given is "... on the prairies of the upper Missouri" (Valley, USA).

According to Campbell and Lamar (2004), a population also exists in southeastern Colorado that is morphologically somewhat intermediate between S. c. tergeminus and S. c. edwardsii.

Conservation status

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.

It is listed in a number of states as an endangered species, although it does not have any designation on the United States 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 state governments.

In Ontario, the species is found only near the eastern shore of Georgian Bay, the Bruce Peninsula, Wainfleet Bog and Ojibway Prairie. Although it also ranges through several American states this is its only range in Canada. 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).

Feeding

The diet consists of a variety of small vertebrates, including mammals, lizards and snakes, as well invertebrates such as centipedes. However, 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 and 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.

Venom

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. In at least one of these cases, the victim was a young child.

Subspecies

Subspecies Taxon author Common name Geographic range
S. c. 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.
S. c. 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, in the Rio Grande Valley, in many of the Gulf Coast counties about as far north as Brazoria, and on several barrier islands including North Padre Island, Matagorda Island and San José Island. Mexico: isolated populations have been reported in the northeast of the country.
S. c. tergeminus (Say, 1823) Western massasauga United States: in the southwestern plains from extreme southeastern Nebraska and northwestern Missouri, southwest through east-central Kansas and west-central Oklahoma into northern and central Texas about as far southwest as the Colorado River.

Gallery

Images of S. c. catenatus:

See also

References

Further reading

  • Ontario Snakes, Ontario Ministry of Natural Resources, Toronto, 1981. Pp. 36.

External links

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