Family Viperidae: This family comprises 150+ species
in 20+ genera distributed on all continents except Antarctica and Australia (Zug, 1993).
Most are heavy-bodied snakes with a distinct head and vertical pupils in the eye. Vipers
possess a pair of hollow
fangs, one on each of the two maxilla bones located beneath the nostrils. The bones and
fangs rotate from a resting position along the roof of the mouth to an erect position by the
mechanical action of lowering the lower jaw. These fangs provide the functional means to
inject modified saliva (venom) deep into prey. Venom glands lie behind the eyes under the
masseter muscle and each is connected to the fang by a hollow duct. Vipers regulate the
amount of venom injected by their control over the masseter muscle. Venom, and the means to
inject it, evolved for the purpose of prey capture, but it is sometimes used as a defensive
measure.
The majority of the species in this family are pit vipers (120+ species); the remaining 50
or so species are true vipers. Each species of pit viper possesses a heat-sensing pit
located between the eye and nostril that is used to aid in prey location. This group is
often classified in the subfamily Crotalinae, although some taxonomists refer them to
full
family status, the Crotalidae. The pit organ contains heat-sensitive cells that are
responsive to changes in temperature of 0.001°C (Halliday and Adler, 1986). This mechanism
probably evolved to allow prey capture in dark spaces, like rodent burrows. A pit viper can
detect the presence of a rodent prey and determine its relative size and distance in total
darkness.
The family Viperidae is represented in Virginia by only three species of pit vipers: the
Timber Rattlesnake (Crotalus horridus), the Eastern Copperhead (Agkistrodon
contortrix) and the Northern Cottonmouth (Agkistrodon piscivorus).
Systematics: Originally described as Boa
contortrix
by Carolus Linnaeus in 1766, based on a specimen sent to him by Alexander Garden from
"Carolina." Schmidt (1953) restricted the type locality to
Charleston, South Carolina. The genus Agkistrodon was first used for this species by
Palisot
de Beauvois in 1799 (Gloyd and Conant, 1990). Early authors interpreted the spelling of the
genus to be either Agkistrodon, following Baird and Girard (1853) and Stejneger and
Barbour
(1917, 1923, 1933, 1939, 1943), or Ancistrodon (Wagler, 1830; Cope, 1860), and thus
the
generic name flip-flopped between these two spellings for well over the last century. In the
Virginia literature, Ancistrodon was used by Cope (1900), Dunn (1915d), Schmidt
(1953), Wood
(1954a), Martin and Wood (1955), Goodwin and Wood (1956), Hutchison (1956), and Reed (1957a,
1957b). Agkistrodon was used by Hay (1902), Dunn (1915a, 1915c), Werler and McCallion
(1951), Conant (1958,1975), Burger (1958), Musick (1972), Mitchell (1974b, 1981a), Martof et
al. (1980), and others. Klauber (1956) showed that Agkistrodon was the most
appropriate
spelling based on the Law of Priority. Baird and Girard (1853) first assigned the specific
name contortrix to Agkistrodon, and numerous authors in the Virginia
literature (noted
above) used the combination Agkistrodon (or Ancistrodon) contortrix.
Description: A medium-sized, heavily bodied snake
reaching a maximum total length of 1,346 mm (53.0 inches) (Gloyd and
Conant, 1990). In Virginia, maximum known snout-vent length (SVL) is 1,094 mm (43.1 inches)
and maximum total length is 1,219 mm (48.0 inches). Tail length/total length in the Virginia
sample was 10.0-16.7% (ave. = 13.3 ± 1.3, n = 185).
Scutellation: Ventrals 140-157 (ave. = 147.9 ±
2.5, n = 214); subcaudals 38-53 (ave. = 45.3 ± 1.5, n = 197) and single, except for 0-17
divided subcaudal scales (ave. = 6.8 ± 4.4, n = 183) near tip of tail; ventrals +
subcaudals 183-203 (ave. = 193.2 ± 3.7, n = 197); dorsal scales strongly keeled, scale rows
23 at midbody; anal plate single; infralabials 10/10 (41.0%, n = 178), 9/9 (27.5%), or
combinations of 8-11 (31.5%); supralabials 8/8 (56.2%, n = 178), 7/7 (14.6%), 7/8 (25.8%),
or combinations of 6-9 (3.4%); loreal scale present;
preoculars 2-3; 4-5 small scales separating eye from supralabials and temporals; temporal
scales variable, generally combinations of 4-7 + 5-7 on both sides.
Coloration and Pattern: Dorsum of body and tail
pinkish tan to dark brown to nearly black with a series of 10-18 (ave. = 14.5 ± 1.5, n =
221) hourglass-shaped crossbands; crossbands chestnut to dark brown, narrow (2-5 scales at
middorsal) in middle and wide laterally; 0-8 bands (ave. = 1.4 ± 1.5, n = 211) may not be
connected at middorsal line and some halves may lack partners altogether; crossbands start
above scale row 1 on each side and are lighter in centers on side and darker at middorsal
area; small, dark-brown blotches-2 scales in diameter or less may be present between
crossbands; most dorsal scales sprinkled with black flecks, which in some snakes may be
quite intense; ventrolateral black spots, below and between crossbands, are all of nearly
equal intensity, except toward tail; venter cream with variable amounts of black flecking
and black smudges; dorsum of head tan to brick red (resembling red Piedmont clay) to brown
and separated from white to cream labial region by a thin, dark-brown line; usually 1 tiny,
dark-brown spot in each of 2 parietal scales on center of dorsum of head; chin cream,
usually without black flecking. The head is somewhat triangular and distinct from the narrow
neck. The dorsum of the head is flat.
Sexual Dimorphism: Adult males reached a larger
average SVL (732.7 ± 153.4 mm, 500-1,094, n = 99) than females (597.8 ± 92.6 mm, 380-952, n
= 80) and reached a longer total length (1,219 mm; females 1,083 mm). Sexual dimorphism
index
was -0.23. The variation in tail length/total length was nearly identical for both sexes
(males 10.0-16.5%, ave. = 13.3 ± 1.3, n = 102; females 10.6-16.7%, ave. = 13.3 ± 1.2, n =
78). Average body mass in adult males (272.9 ± 136.4 g, 91-525, n = 15) was greater than
that in adult females (178.1 ±
69.6 g, 103-318, n = 7).
The average number of ventral scales was similar between sexes (males 147.8 ± 2.2, 140-154, n
= 118; females 148.1 ± 2.6, 141-157, n = 91), as was the average number of body crossbands
(males 14.5 ± 1.5, 11-18, n = 121; females 14.6 ± 1.5, 10-18, n = 95). The average number of
subcaudals was slightly higher in males (46.4 ± 2.5, 38-53, n = 108) than in females (44.0 ±
2.3, 38-52, n = 84). A similar pattern was expressed in the average number of ventrals +
subcaudals (males 194.4 ± 3.3, 185-201, n = 108; females 192.0 ± 3.7, 183-203, n = 84).
There are no apparent sexual differences in color or pattern.
Juveniles: Juveniles are colored and patterned as
adults, with the notable exception that the tip of the tail (about 25-30% of its length) is
sulfur yellow. Juveniles lack the black flecking seen in adults; it appears with
age. Neonates had a SVL of 170-205 mm (ave. = 196.5 ± 8.7, n = 17), a total length of
204-243 mm (ave. = 233.2 ± 8.7, n = 16), and an average body mass of 7.0 g (mean for one
litter). Gloyd and Conant (1990) reported that newborn A. contortrix had a total
length of
190-280 mm and weighed 7.2-9.4 g.
Confusing Species: Many people in Virginia call
almost every snake with a pattern an Eastern Copperhead. Corn Snakes (Pantherophis
guttatus) have a series
of chestnut-brown blotches, each surrounded by black, along the dorsum; a gray to
reddish-brown background; a conspicuous eye-jaw stripe; and a black-and-white checkerboard
venter. Eastern Milk Snakes (Lampropeltis triangulum) have brownish blotches on a
gray to gray-brown
background and either a black-and-white checkerboard pattern or extensions of the dorsal
pattern on the venter. Juvenile Eastern Ratsnakes (Pantherophis alleghaniensis),
often killed for
Eastern Copperheads, have a series of dark-brown blotches on a grayish-white background and
a dark
eye-jaw stripe. The Northern Cottonmouth (Agkistrodon piscivorus) is darker and has
broad, dark-olive to black crossbands on a
yellowish to olive background, a dark-olive to yellowish-olive head, and a black tail.
Juvenile Northern Cottonmouths have the yellow tail tip and broad crossbands on a pinkish to
brownish
background.
Geographic Variation: The average number of ventral
scales (males and females combined) varied from 144.2 ± 2.7 (141-148, n = 6) in the
Appalachian Plateau to 148.5 ± 2.7 (144-153, n = 19) in the lower Piedmont, except for the
sample from the southern Blue
Ridge Plateau, which averaged 150.8 ± 3.1 (148-156, n = 5) . The average number of
subcaudals (entire + paired) ranged from 44.2 ± 3.7 (38-49, n =
17) in the lower Ridge and Valley region to 45.8 ± 2.9 (42-53, n = 42) in the southern
Coastal Plain. The number of divided (paired) subcaudals varied from a low of 5.0 ± 1.6
(3-7, n = 4) in the southern Blue Ridge Plateau to a high of 8.8 ± 2.7 (6-13, n =
6) in the Ridge and Valley north of the New River and 8.8 ± 5.3 (1-15, n = 6) in the
Appalachian Plateau.
The average number of body crossbands varied from 14.0 ± 1.1 (12-17, n = 44) in the southern
Coastal Plain to 15.7 ± 0.5 (15-16, n = 6) in the Appalachian Plateau. Individuals of Agkistrodon
contortrix with 1-3 broken crossbands are common
throughout Virginia. Fourteen specimens with 4-6 broken crossbands were collected from the
lower Coastal Plain, the upper and lower Piedmont, and in Shenandoah National Park in the
Blue Ridge Mountains. One A. contortrix specimen from Lunenburg County, in the lower
Piedmont, had 8 broken crossbands, and one from Botetourt County, in the northern Blue Ridge
Mountains, had 7. The width of the midbody
crossband at the middorsal line varies from 2 to 5 scales; widths of 1 or 6 are rare. Counts
of 2-3.5 are common throughout Virginia. The higher counts of 4-5 are commonly found in
snakes from the Blue Ridge Mountains westward; counts of 2-4 have been recorded for snakes
from southeastern Virginia.
Geographic variation in Virginia A. contortrix is expressed primarily in body color
and
pattern. Snakes from southeastern Virginia have brown to dark-tan crossbands on a light-tan
to pinkish background, and reddish-tan heads; those from the Piedmont have dark-brown or
chestnut crossbands on a reddish-brown to grayish-brown background, and reddish heads (much
like the color of Piedmont clay); and those from the mountains and Ridge and Valley have
dark-brown or chestnut crossbands on a brown to grayish-brown body, with heads of various
shades of brown. Snakes from the extreme southwestern region of Virginia and many snakes
from the mountains possess considerable black flecking over the body, producing in some
cases a very dark snake. These are general differences, as individuals in any region may
show extremes in color. Individual specimens of Agkistrodon contortrix from the
Piedmont and
mountains often exhibit a series of lateral brown spots alternating with the dorsal
crossbands. Snakes in southeastern Virginia usually do not possess this character.
Biology: Eastern Copperheads are terrestrial snakes
inhabiting a wide array of habitats. They are found in hardwood and mixed hardwood-pine
forests, pine woods, abandoned fields in various stages of succession, high ground in swamps
and marshes, forest-field ecotones, hedge rows, suburban woodlots, ravines along creeks in
agricultural and urban areas, upland rocky areas, rock walls and woodpiles, and forested
dunes near beaches, as well as around barns and houses (especially dilapidated ones) in
agricultural areas. Musick (1972) noted that blueberry thickets are favored habitat. In
Pennsylvania, Reinert (1984a, 1984b) found that A. contortrix utilized relatively
open areas
with higher rock density and less surface vegetation than the sympatric Timber Rattlesnake
(Crotalus horridus). This probably pertains to upland Virginia habitats as well. I
have
found them coiled under vegetation in orchards and on farms. Habitat requirements appear to
be sunlit areas with sources of prey (see below), and year-round shelter. Such places are
often found near human
habitation, and A. contortrix will take advantage of these situations. Eastern
Copperheads will
seldom climb high into vegetation but will swim when necessary.
Agkistrodon contortrix is diurnal and nocturnal during warm weather (generally May
through
September), depending on the temperature, and is primarily diurnal in the cooler seasons.
Movement is stimulated by rains and the urge to mate and seek food. The normal seasonal
activity period is 9 April through 30 October (museum records). Clifford (1976) recorded
active snakes from May to October in Amelia County. Wood (1954a) reported that individuals
of A. contortrix were seen from 16 April to 12 December in Shenandoah National Park,
but
that it was uncommon to find them earlier than May or later than September. Elevation
influences the length of the activity season. Eastern Copperheads often overwinter in
aggregations
in dens, sometimes shared with Crotalus horridus (Wood, 1954a) or Coluber
constrictor (C.
H. Ernst, pers. comm.), in the mountains, but in small numbers or singly in the Piedmont,
Coastal Plain, and low-elevation valleys in the Ridge and Valley region.
Eastern Copperheads are predators of many types of prey. What they eat depends on the size of
the
snake and the types of prey available. Juveniles consume more invertebrates than adults,
whereas adults eat more small mammals. In their study in the George Washington National
Forest, Uhler et al. (1939) found the following prey in 72 specimens: meadow voles (Microtus
pennsylvanicus), woodland voles (Microtus pinetorum), southern red-backed
voles
(Clethrionomys gapperi), southern bog lemmings (Synaptomys cooperi),
white-footed mice
(Peromyscus leucopus), jumping mice (Zapus or Napaeozapus), chipmunks (Tamias
striatus),
unidentified squirrels, northern short-tailed shrews (Blarina brevicauda), least
shrews
(Cryptotis parva), masked shrews (Sorex cinereus), hairy-tailed moles
(Parascalops breweri), ruby-throated hummingbirds (Archilochus colubris), an
unidentified
warbler (Dendroica spp.), an unidentified passerine bird, Slimy Salamanders (Plethodon
glutinosus = cylindraceus), Red-backed Salamanders (Plethodon cinereus), Red
Salamanders
(Pseudotriton ruber), an unidentified frog (Lithobates spp.), Fence Lizards
(Sceloporus undulatus),
Eastern Wormsnakes (Carphophis amoenus), moth caterpillars, and cicada nymphs. De
Rageot
(1957) reported a Dismal Swamp short-tailed shrew (Blarina brevicauda telmalestes)
from an
Eastern Copperhead collected in the Dismal Swamp. I found a star-nosed mole (Condylura
cristata) in
a specimen from Giles County. To this list C. H. Ernst (pers. comm.) added skinks (Plestiodon
spp.) and Eastern Garter Snakes (Thannophis sirtalis). Predators of Eastern
Copperheads are not
well known. Megonigal (1985) reported the predation of a Dismal Swamp adult by an Eastern
Kingsnake (Lampropeltis getula). W. H. Martin (pers. comm.) observed a broad-winged
hawk
(Buteo platypterus) catching an Eastern Copperhead by a rock wall along the Skyline
Drive in
Rockingham County. Gloyd and Conant (1990) listed Northern Black Racers (Coluber
constrictor), Eastern Milksnakes (Lampropeltis triangulum), and Kingsnakes of
both Virginia species (L. getula, L. nigra) as ophiophagus predators. Numerous
individuals are also killed each
year on Virginia's highways.
Agkistrodon contortrix is viviparous. Mating, described in Schuett and Gillingham
(1988) and
Ernst (1992), occurs in spring and fall. Gloyd and Conant (1990) noted that mating is
"frequent during the first few weeks following cessation of hibernation and occasional
throughout the active season, especially during the autumn." W. H. Martin (pers. comm.)
observed mating in Loudoun County, Virginia, on 26 May 1977 and a male "courting" a dead
(DOR) female on the Skyline Drive, Rockingham County, on 15 September 1974. C. H. Ernst
(pers. comm.) observed mating on 24 April 1985 in Fairfax County. Mating is sometimes
preceded by male combat (Mitchell, 1981a; Ernst, 1992). Gloyd (1947) recounted the following
observation made by Joseph Ackroyd
near Winchester, Frederick County, in late July 1945 (only the actual behavior is reported
here):
Possibly two-thirds of the anterior portions of the snakes' bodies were entwined
vertically
with the exception of a portion of the neck. The heads were opposite each other and were
held horizontally, three or four inches apart. They seemed to gaze hypnotically at each
other and there was a slight swaying movement between them. About one turn of coil was
wound
and unwound, first in a clockwise and then in a counterclockwise direction. At no time
did
the distance between the heads change during the rhythmic movements, and at no time did
the
snakes progress along the ground. It seemed as if the posterior ends were definitely
"anchored."
On three distinct occasions one of the snakes broke the rhythm of the dance by darting
its
head rapidly at the other. The visibility was not good but I imagined the movement to be
a
caress, with contact made somewhere in the region of the chin of the other snake.
What most amazed me was their utter disregard for me. I watched them from a distance of
about three feet, engulfed them in the rays of the light for minutes, and yet the dance
continued. From the time I first saw them until they were prodded with a stick and moved
off
into the underbrush, approximately twenty minutes elapsed.
The smallest mature male from Virginia had a SVL of 475 mm and the smallest female a SVL of
375 mm (S. J. Stahl and J. C. Mitchell, unpublished). Ovulation occurs in late May to early
June, and birth usually occurs from late August until early October. Known birth dates are
between 10 August and 6 October. W. H. Martin (pers. comm.) observed spent females and
newborn young at montane den sites in Virginia between 22 August and 22 September, and a
gravid female on 6 October. Litter size in Virginia was 3- 15 (ave. = 7.6 ± 3.9, n = 18),
but 1-21 rangewide (Ernst, 1992). Dunn (1915c) reported the first notes on reproduction in
this species in Virginia: 7 neonates born 1 September 1913 in Nelson County. Wood (1954a)
reported birth dates of 26 and 28 September and litter sizes of 6 and 7.
Eastern Copperheads appear to be more abundant in the mountains than in the Piedmont or
Coastal
Plain. Uhler et al. (1939) recorded 213 copperheads in a sample of 885 from the George
Washington National Forest. Martin (1976) reported it to be the most abundant snake that he
observed in the Blue Ridge Mountains in a 3-year period: 243 out of 545 snakes recorded.
Clifford (1976) recorded only 17 Eastern Copperheads out of 278 snakes in Amelia County in a
4-year
study. Werler and McCallion (1951) noted they were "apparently uncommon" in Princess Anne
County (= City of Virginia Beach). Quantitative studies of population size have not been
performed in Virginia. Fitch (1960) found a density of 6-9 snakes per hectare in a Kansas
population in which estimated natural longevity was 13 years and average annual adult
survivorship was 71%.
Eastern Copperheads will vibrate their tails when disturbed but will usually remain alert and
motionless, especially if found under vegetation or in other diurnal retreats (Wood, 1954a).
The characteristic alert pose at rest is with the body coiled and the head elevated at a 45°
angle. They are usually docile when caught but will strike on provocation. Very warm
Eastern Copperheads, such as those encountered on a hot summer road, are apt to be
pugnacious.
Remarks: Other common names in Virginia are highland
moccasin (Dunn, 1915a, 1918); copperhead moccasin (Dunn, 1936; Burch, 1940); moccasin
(Carroll, 1950); pilot snake, chink head, and upland moccasin (Linzey and Clifford, 1981);
and
poplar leaf (Brothers, 1992). Gloyd and Conant (1990) noted that the term "moccasin" is used
incorrectly to refer to several species of snakes, including the nonvenomous water snakes
(Nerodia), and suggested that the term not be used at all.
Agkistrodon contortrix is the least venomous of
the three venomous snakes in Virginia. As far as I can ascertain, no one in recorded
Virginia history has died from the bite of this species. A summary of snakebite patterns and
treatment is presented in the section "Venomous Snakebite."
Beck (1952) noted that a Rappahannock County myth claimed that Eastern Copperheads, like all
venomous reptiles, inflicted a wound into which they "blew" green venom from tubes. Thus,
removal of fangs would render the snake only slightly less dangerous.
Conservation and Management: Agkistrodon
contortrix
is not a species of special concern in Virginia because of its abundance and widespread
distribution. Like all snakes, Eastern Copperheads play important roles in the economy of
nature and
should be removed from human-inhabited areas, not killed. Maintenance of this species in a
natural biotic community requires an abundance of small mammal prey, open areas with hiding
places that can be used for basking, and overwintering sites that allow the snakes to
hibernate below the frost line.
Eastern Copperheads have dark colored crossbands that are for the most
part shaped like an hourglass.
Usually some of the crossbands are broken and do not connect.
While close inspection of a snake's face and/or it's anal plate is a definitive way to distinguish a
venomous snake from a harmless species, it requires one to get dangerously close to a potentially
dangerous animal. It is far better to learn the pattern and coloration of a few snakes so that a
specimen may be identified from a safe distance.
Probably the most common snake misidentified as a copperhead is the
harmless juvenile eastern ratsnake (formerly called the blackrat snake). The eastern ratsnake
starts life with a strong pattern of gray or brown blotches on a pale gray background. As the
eastern ratsnake ages the pattern fades and the snake becomes black, often with just a hint of
the juvenile pattern remaining.
Around late August to mid October depending on the temperatures, eastern
rat snakes look for a nice warm place to wait out the upcoming winter. Frequently these snake
will choose a house attic, crawlspace or basement. Luckily, copperheads don't usually seek
winter refuge in human occupied dwellings.
______________________________________________________________
Like the Eastern Ratsnake, Black Racers are also born with a blotched
pattern. However, unlike the Eastern Ratsnake that may retain the juvenile pattern for several
years, the pattern of the Black Racer usually fades to a uniformed black within the first two
years of life. Juvenile Black Racers usually do not seek winter refuge in human occupied
dwellings. Black Racers are usually one of the first snakes to become active when spring
arrives.
______________________________________________________________________________________________
Juvenile and subadult Northern Watersnakes have a pattern that can vary
greatly in color, from dark grayish to a reddish brown. The color of some individuals
watersnakes can come close to that of some copperheads, however the pattern on the Northern
Watersnake is always narrow on the sides and wide near the backbone. This is completely opposite
of the pattern found on the Eastern Copperhead (wide on the sides and narrow near the back
bone). Some adult Northern Watersnakes retain a strong, distinct juvenile pattern while others
become a uniformed brown. As the name implies, the Northern Watersnake is usually found in close
proximity to water.
_______________________________________________________________________________________________
The pattern of the eastern milksnake is fairly consistent in Virginia,
however the intensity of the colors can vary quite a bit. Usually the blotches across the back
are outlined in black. Eastern Milksnakes are found statewide, but are more abundant in the
mountainous regions.
_____________________________________________________________________________________________
Eastern Hog-Nosed snakes are the great actors of the snake world. In an
effort to ward off predators these snakes will puff-up, hiss loudly, spread their neck and
strike with the mouth closed. If all else fails the Hog-nosed Snake will roll over and play
dead. Found statewide the pattern and coloration of these snakes can vary greatly. Eastern
Hog-noses Snakes prefer sandy soil and primarily feed on toads.
_____________________________________________________________________________________________
The Red Cornsnake also known as the red ratsnake is usually more brightly
colored and and has a more reddish hue than that of the copperhead. The pattern of the Red
Cornsnake is a blotch that does not extend down the sides to the ground. Unlike the juvenile
pattern of the eastern ratsnake that fades as the snake ages, the pattern of the Red Cornsnake
remains distinct regardless of age.
_____________________________________________________________________________________________
Juvenile Northern Mole Kingsnakes have a strong pattern that usually,
but not always fades to a uniformed brown as the snake ages. Northern Mole Kingsnakes are seldom
seen out in the open and are general found under surface cover (plywood, tin, flat rocks,
etc..). Northern Mole Kingsnakes will sometime venture out in the open after a heavy rain.
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