‹ Compare two snakes
Eastern Massasauga vs Western Massasauga
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erinsuzanne, no rights reserved
Eastern Massasauga
Sistrurus catenatus
Venomous(c) Meghan Cassidy, some rights reserved (CC BY-SA)
Western Massasauga
Sistrurus tergeminus
VenomousThe quick way to tell
Look at where you are first. The Western lives on the plains and in the Southwest; the Eastern lives from the Great Lakes region west to eastern Iowa and Missouri, and only in Iowa and Missouri do both occur. If you can see the belly safely, the Eastern's is mostly black with light marks, while the Western's is usually pale cream or gray with dark flecks.
Pattern ★ This settles it
Large dark brown squarish blotches down a gray back, smaller spots along the sides.
Rows of dark brown blotches on gray or tan, with smaller spots along the sides.
Head
Small triangular head with nine large plates on top and a dark stripe through the eye.
Triangular head with nine large, plate-like scales on top — unlike most rattlesnakes, which have many small scales there. A white-edged dark stripe runs from the eye to the jaw.
Eyes
Vertical slit pupil; heat-sensing pit between eye and nostril.
Vertical slit pupil; heat-sensing pit between eye and nostril.
Pits
A deep heat-sensing pit on each side of the face, between the eye and the nostril.
A deep heat-sensing pit on each side of the face, between the eye and the nostril.
Tail
Small, with a tiny buzzy rattle.
Banded light and dark ahead of a small rattle; babies have a yellowish tail tip.
What it does
Freezes and stays still; rarely rattles or strikes.
Usually lies still when approached; some rattle at the least disturbance and strike.
Where it lives
Great Lakes region and upper Midwest: western New York, western Pennsylvania and Ontario west through Ohio, Michigan, Indiana, Illinois and Wisconsin to eastern Iowa (now gone from Missouri and Minnesota).
Central plains from southwestern Iowa, northwestern Missouri and southeastern Nebraska south through Kansas and Oklahoma into Texas, and west into Colorado, New Mexico and far southeastern Arizona.