Daniel Heuclin / Desert massasauga snake (Sistrurus catenatus edwarsii) in desert, West Texas, USA, September.

Barry Mansell / Western Massasauga Rattlesnake (Sistrurus catenatus). Arizona, USA, September.

Mary McDonald / Western Massasauga pygmy rattlesnake {Sisturus catenatus tergeminus} Texas, USA. Captive

Michael & Patricia Fogden / Massasauga (Sistrurus catenatus) at burrow of Bannertail Kangaroo Rat (Dipodomys spectabilis) grasslands, Arizona

Michael & Patricia Fogden / Massasauga (Sistrurus catenatus) at burrow of Bannertail Kangaroo Rat (Dipodomys spectabilis) grasslands, Arizona

Michael & Patricia Fogden / Massasauga (Sistrurus catenatus) in grass, southeastern Arizona

LYNN M. STONE / Eastern massasuga rattlesnake juvenile {Sistrurus catenatus catenatus} captive, USA

Barry Mansell / Western massasauga (Sistrurus catenatus) rattlesnake coiled on sand with head raised, Arizona, USA.