This shy, reclusive, nonaggressive rattlesnake used to live in floodplain wetlands of the Mississippi, Missouri and Grand rivers, but as those wetlands have been drained and destroyed, the massasauga has disappeared with them. Now it is an endangered species.
Copperheads are pit vipers, with an opening on each side of the head and (in daylight) eyes with catlike, vertical pupils (our nonvenomous snakes have round pupils).
Missouri’s largest venomous snake is dangerously venomous, but there are few cases of rattlesnake bites in our state. It frequents rough country, is mostly nocturnal in summer and few Missourians ever encounter it.