Eastern Massasauga (Rattlesnake) Sistrurus catenatus - Endangered

Gravid female from LaGrange County

Identification

Indiana's smaller rattlesnake is rare and unlikely to be encountered outside of the few remaining fens and wetlands in northern Indiana where it persists. Eastern Massasaugas, though small, are relatively heavy-bodied and typically gray to light brown in color. They have dark brown blotches down the back and a broad, dark stripe along the side of the head and through the eye. Despite their name, this small rattlesnake's rattle is only audible in large adults and is relatively quiet, like a bumblebee trapped under a glass. Adult Eastern Massasaugas are small, rarely exceeding two feet (60 cm) in length.

Gravid female from LaGrange County
Adult from southern Michigan

There are a few gray-brown blotched snakes that are sometimes mistaken for Eastern Massasaugas, including Northern Watersnakes, Eastern Hog-Nosed Snakes, Eastern Milksnakes, and Eastern Foxsnakes. Both Eastern Milksnakes and Eastern Foxsnakes are more slender and have smooth to weakly keeled scales and all aforementioned species lack the distinctive dark, broad stripe through the eye that Eastern Massasaugas have. The small keratinous rattle at the tip of an Eastern Massasauga's tail is also unique to this species in northern Indiana.

All four of Indiana's venomous snakes have thick bodies, broad chunky heads, elliptical pupils, heat sensitive pits between the eyes and nostrils, and undivided post-anal ventral scales (under the tail). However, most of these characteristics require close examination, elliptical pupils can dilate and become round, and many non-venomous snakes (especially Eastern Hog-Nosed Snakes) will broaden and flatten their heads in self-defense. Therefore, it is always best to treat any snake that you cannot positively identify as potentially venomous. Venomous snakes are best left alone as most snake bites occur when someone attempts to handle or kill the snake. Snakes are not aggressive and do not hunt, attack, or chase people when left unmolested.

Ecology and Conservation

Eastern Massasaugas are unusual among rattlesnakes in that they rely heavily on wetland habitats. Eastern Massasaugas from many populations utilize drier upland habitats during the summer months. Within upland habitats, Eastern Massasaugas generally associate with areas of more open vegetative structure, such as meadows and old fields. In general, closed canopy forests are avoided, and snakes that do enter these habitats are often located where light gaps penetrate the forest canopy. The diet of the Eastern Massasauga consists primarily of warm blooded prey, such as small rodents (voles, jumping mice, and shrews); however birds and frogs may also occasionally be taken. Interestingly, male Eastern Massasaugas have been observed to display competitive “combat” behavior during the summer courtship period, much like other rattlers. Eastern Massasaugas primarily overwinter in crayfish burrows, but will also utilize other crevices such as at the bases of sphagnum hummocks or rotted trees. Eastern Massasaugas have been demonstrated to show high fidelity to their hibernacula, returning to the same area year after year.

Grassy fen in Carrol County
Spring-fed fen in LaGrange County

Continued habitat degradation, loss, and fragmentation pose the greatest threat to Eastern Massasauga populations. Roads can be a major source of mortality in many populations. Eastern Massasaugas are often intentionally killed due to the fact that they are venomous and present a presumed risk to humans. Illegal collection for the pet trade is also a factor cited in Eastern Massasauga declines. The Eastern Massasauga is listed as state Endangered in all Midwest states save Michigan, where it is considered a species of Special Concern. As a result of the tremendous declines experienced by this species, the Eastern Massasauga has been added to the U.S. Fish and Wildlife Service’s Candidate Species List. Candidate species are threatened by extinction in the foreseeable future and await listing as threatened or endangered under the Endangered Species Act of 1973.

Distribution

Eastern Massasaugas are found in grassy fens, wetlands, and remnant wet prairies of northern Indiana. Though they were once found throughout much of the northern half of the state and possibly further south, populations declined sharply following the extensive transformation of grasslands and wetlands in Indiana to agricultural land during the mid-1900's. They are now restricted to a few, scattered remnant populations in the northernmost part of the state and are apparently still declining. This trend of decline is not unique to Indiana and, as such, Eastern Massasaugas are now listed as federally threatened and are state endangered in Indiana.

Taxonomy

Some scientists recognize one species and three subspecies of massasauga rattlesnake; others recognize two distinct species, one with two subspecies and the other with one. Regardless, Indiana's massasaugas belong to the species S. catenatus, and if the former system is subscribed to, they belong to the Eastern Massasauga (S. c. catenatus) subspecies. These snakes are members of the family Viperidae, which is represented by a total of four species in Indiana.

Literature Cited

Conant, R. and J. T . Collins. 1998. Reptiles and Amphibians of Eastern and Central North America. Third Edition, Expanded. Houghton Mifflin, New York, NY.

Minton, S. A. Jr. 2001. Amphibians and Reptiles of Indiana. Indiana Academy of Science, Indianapolis, IN.

Distribution Map
Distribution map of Eastern Massasauga (Rattlesnake) (Sistrurus catenatus)
Photographs