Four Eastern Pit Vipers

     Over the years, I have seen a few each of timber rattlesnakes and copperhead snakes sunning themselves in wooded, rocky hills in my native Pennsylvania.  Those beautiful snakes are always a thrill to experience because they are not often seen and they can be dangerous to people.      
     Four kinds of vipers live in the eastern United States, including timber rattlesnakes, eastern diamond-backed rattlesnakes, copperhead snakes and cottonmouth moccasins.   These related snakes are called pit vipers because they have a heat sensory pit between each eye and nostril that detects warm-blooded prey.  They also have heads noticeably thicker than their necks, because of their poison glands, thick bodies and vertical pupils.  Being cold-blooded, all species bask in sunlight to warm up for the day's activities and are camouflaged in their natural habitats, making them difficult to see.  All are predatory, using venom produced in glands in the backs of their heads to kill their victims.  All bear young alive.  And, although they are dangerous to people, they are beautifully marked and have interesting life histories. 
     Timber rattlesnakes and diamond-backs, like all their rattlesnake kin, have "rattles" of loosely connected, modified skin that makes a buzzing noise when these snakes become frightened or irritated.  The sound of those rattles often warns people and animals of the presence of rattlesnakes before those serpents are seen.
     Timber rattlesnakes live in rocky, wooded hillsides from New England south in the eastern United States.  Generally, they are yellow, brown, gray or black with dark back and side markings and black tails.  They lie along logs in woodlands to ambush chipmunks, squirrels, mice and small birds.  They are most active at night during summer.
     Timber rattlesnakes mate in spring and fall.  Females mature in four to five years and give birth in autumn to 5 to 17, 12-inch young every other year.  They bask in sunlight as much as they can to warm themselves so their embryos will grow faster.  They don't eat anything when they are pregnant so they fatten up during the in between years.
     In the northern part of their range, timber rattlesnakes congregate in rocky dens to pass the winter in relative safety.  Black rat snakes and copperhead snakes join them in some of those retreats. 
     Eastern diamond-backed rattlesnakes are the largest of their kind in the United States, and the most dangerous.  They range from southern North Carolina to Florida and the southern half of the Deep South states to Mississippi.  They are basically brown with dark diamonds on their backs that have light centers and are bordered by yellow.  They mostly live in longleaf pine and sand hill pine woods, and oak woods in bottomlands.  They shelter in gopher tortoise burrows and other holes in the ground, and in clumps of saw palmettos.  They eat rabbits, squirrels, mice, birds and other, smaller creatures. Female diamondbacks give birth to 7 to 20, 14 inch young from July to October.  
     Copperhead snakes are light-brown with reddish-brown cross-bands on their backs that look like hourglass figures.  And they have coppery heads.  They inhabit wooded hills with rock outcroppings above streams and swamps from the Mid-Atlantic States to the Gulf States to eastern Texas.  They like to hang out in stone walls, brush piles, rotting logs and other sheltered places in the woods.  They are mostly nocturnal in summer and lie along logs to ambush mice, chipmunks, lizards, frogs and other small critters.  Young copperheads twitch their yellow tails to lure prey to them.  This species hibernates for the winter in dens in rock outcroppings, sometimes with timber rattlesnakes. 
     Copperheads mate in the spring and fall.  Females give birth to one to 14, nine-inch young from August to October.  The young mature in two to three years.
     Cottonmouths are southern vipers, living in swamps, along creeks and other bodies of fresh water from southern Virginia to Florida to west Texas and Arkansas.  They are so-named for the white lining of their mouths they display as a threat to would-be harassers.  This species is related to copperheads, but have a more deadly venom.  Young moccasins have yellow tails, as do young copperheads. 
     Cottonmouths are olive, brown or black above with a wide, dark-brown cheek stripe on some individuals.  Young are more strongly patterned.  They are most active at night when they consume frogs, snakes, birds small fish and other prey. 
     Female moccasins mature in three years.  They mate in spring and autumn and give birth to one to 15, 11 inch young in August or September.  And like all these vipers, give birth every other year and feed during the between years. 
     Even if these pit vipers are never seen, it's interesting to note they exist in the eastern United States.  To avoid them, stay away from places where they seek shelter.