Desert Massasauga Rattlesnake
Sistrurus tergeminus edwardsii
Federal and State Protections
Federally protected in Mexico
State protected in Arizona & Colorado
Countries of Occurrence
31cm (12in) - 59cm (23.2)
States or Providence
US: Texas, New Mexico, Arizona, Colorado, possibly extreme SW Kansas
Mexico: Coahuila, Nuevo Leon
The desert massasauga is a small subspecies rattlesnake found in the central-western US and northern Mexico. It is the smallest of the massasaugas, with adults maxing out at around 58-59cm total length.
Arid sage scrublands and shortgrass prairies are the main habitat of this species, but they can also be found in lightly vegetated sand dune habitat. Studies from Colorado have also found that grasslands sporadically grazed by domestic cattle remain suitable habitat for this subspecies. It is the westernmost representative of the genus Sistrurus, and considered one of the rarest species in Mexico.
In terms of size, it is slightly smaller and skinner than its sister subspecies, S. t. tergeminus, the western massasauga; though the two subspecies are known to intergrade/cross-breed in areas of overlap in Texas.
They are threatened by human persecution and road mortality. Snakes moving between winter hibernacula and summer foraging sites are increasingly at risk of being hit by vehicles when crossing roads.
Fun fact: This subspecies is named for Colonel-Dr. Lewis Edwards, a US Army surgeon who collected and donated the first type specimen.