Copperheads, Agkistrodon contortrix, belong to a subfamily of venomous snakes, known as pit vipers, which also includes the cottonmouth and rattlesnakes. An important characteristic they share with other pit vipers are infrared-sensing facial pits, which are small openings between the eye and nostril on each side of the head. These pits assist in locating warm-blooded prey, such as mice.
Look into a pit viper's eyes and you'll see pupils shaped like cat's-vertical and elliptical. All venomous snakes in Missouri-including copperheads-are pit vipers. If you see a snake with round pupils, it is a nonvenomous species. Copperheads and other members of their family have hollow, folding fangs located on the forward part of their upper jaw that allow them to inject venom into their prey.
Copperheads and their relatives (members of the genus Agkistrodon) have a wide distribution, with species living in Asia, Malaysia, southeastern Europe, North America and Central and South America. In the U.S., copperheads range from southern New England to northern Florida and west to southern Indiana, western and southern Illinois, Missouri, southeastern Nebraska and southwest through much of Oklahoma and Texas.
There is not just one kind of copperhead; North America actually has five regional races or subspecies, which differ in coloration and geographic location. One western subspecies even ranges into extreme northern Mexico. Missouri is at a crossroads between several of these subspecies.
Those living in extreme southern Missouri have characteristics of the southern copperhead. The Osage copperhead lives throughout the rest of the state, except for a few counties bordering Iowa. There are blends or intergradations of these races in southern and eastern Missouri.
Missouri's copperheads are pinkish tan with distinct, dark brown markings along their backs that are shaped like a bow tie or hourglass (pinched in the middle and wide on either side). Southern copperheads have more tan than pink in the background color, and their markings have less brown and are more constricted on the top. Osage copperheads usually have a light tan or white border around each dark marking against their pinkish tan background.
Newborn copperheads and those under two years of age are slightly paler, but they still have the same markings. Young copperheads have sulphur yellow tails. This coloration is gone when they are 2 years old. Copperheads of all ages have a dark marking on the sides of the head bordered by a thin black line and a cream or white line. This marking and