attempts at first aid result in brutally deep incisions and tourniquets
applied too tightly and for too long a period of time; the resultant
damage in many instances exceeds that of the bite itself (Stimson and
Engelhardt, 1960:165). Stimson and Engelhardt also think that time
should be sacrificed to surgical cleanliness, and incisions should not
be made if a hospital can be reached within an hour.
The ligature-cryotherapy (L-C) method proposed by Stahnke (1953) has
been severely criticized by other workers. He stated that the ligature
should be tight enough to restrict completely the flow of venom until
the temperature of the area can be lowered sufficiently to prevent any
action of the venom. After 10 minutes the ligature may be removed and
the bitten area kept immersed in a vessel of crushed ice and water. If
the envenomized member is to be treated for more than four hours (which
is the case with almost all pit-viper bites), it should be protected by
placing it in a plastic bag. The venom action should be tested after 12
or more hours. This consists of a brief warming period to determine
whether or not the action of the venom can be felt. The patient should
be kept warm at all times; and the warming at the termination of
treatment should be done gradually, preferably by allowing the water to
warm slowly to room temperature.
Advocates of the L-C method warn against making incisions unless they
are absolutely necessary, the theory being that each cut permits
additional bacterial infection and does little good in removing venom.
However, McCollough and Gennaro (1963:963) demonstrated that, in bites
where the fangs had only slightly penetrated the skin, more than 50 per
cent of the venom was removed in some instances if suction was started
within three minutes after the injection. With deeper injection the
amount of venom recovered sometimes reached 20 per cent of the dose.
Stahnke suggested that an incision be made at the site of the bite only
after the site has been refrigerated for at least 30 minutes.
Stimson and Engelhardt (_loc. cit._) stated that two constricting bands
should be used between the bite and the body and that cracked ice in a
cloth should be applied to the bite before reaching a hospital. In
addition, they suggested the following procedure. Rings of incisions
should follow the swelling, and suction should continue for several
hours. After the edema has receded, the limb should be wrapped in a
towel containing crushed ice. Antivenin should be given only in severe
cases. Calcium gluconate and gas gangrene antitoxin as well as
antibiotics are helpful.
The most recent and up-to-date summary of snakebite treatment is that by
McCollough and Gennaro (1963). Following is a brief summary of their
suggestions:
1. Immobilization--Systemic immobilization is effected by body
rest and locally by splinting the bitten area.
2. Tourniquet--A lightly occlusive tourniquet during a 30- to
60-minute period of incision and suction would seem to possess
some advantages. In severe cases where medical attention is
hours away, a completely occlusive tourniquet may be necessary
to prevent death. Sacrifice of the extremity may be necessary
for the preservation of life.
3. Incision and suction--Suction should begin three to five
minutes after injection of venom if symptoms of poisoning are
present. Incisions one-fourth inch to an inch long across each
fang mark should be made in order to open the wound for more
efficient suction. Multiple incisions are not useful for the
removal of venom but may be employed under hospital conditions
to reduce subcutaneous tensions and ischemia.
4. Cryotherapy--An ice cap over the site of the bite for relief
of pain would seem to be permissible, especially prior to the
administration of antivenin. It must be remembered that cooling
during the administration of the antivenin radically reduces
the access of the antiserum to the bite area.
5. Antivenin--Antiserum is the keystone to the therapy of
snakebite. Careful evaluation of the severity of the bite and
the patient's sensitivity should be made before the use of
antivenin. In Grade II (moderate) bites, the intramuscular
injection on the side of the bite may suffice. In Grades III
(severe) and IV (very severe), shock and systemic effects
require intravenous injection. In bites producing symptoms of
this severity, antivenin must be given in amounts large enough
to produce clinical improvement. Ten to 20 units may be
necessary to prevent the relapse that sometimes occurs after
small doses of antivenin. Permanent remission of swelling and
interruption of necrosis are the therapeutic end point in the
clinical use of the antiserum.
In all cases of snakebite where there is any doubt as to the snake's
identity, it should be killed if possible and taken to the hospital for
positive identification. In many instances of actual bites by poisonous
snakes the only treatment needed was an injection of tetanus antitoxin
or toxoid and sedation, because physical examination revealed no
indication of poisoning (Stimson and Engelhardt, _loc. cit._).
Case History of a Bite
On July 29, 1963, at 8:20 a.m., I was treating a nine-month-old
cottonmouth for mites. As I dropped the snake into a sink, it twisted
its head and bit the tip of my right middle finger with one fang. The
fang entered just under the fingernail and was directed downward, the
venom being injected about five millimeters below the site of fang
penetration. After placing the snake back in its cage, I squeezed the
finger once to promote bleeding, wrapped a string around the base of the
finger, and drove to Watkins Memorial Hospital on the University of
Kansas campus. I began to feel a burning sensation in the tip of the
finger almost immediately. Upon my arrival at the hospital, an
additional ligature was placed around my wrist. At 8:30 a.m. a small
incision was made in the end of the finger, which by this time was
beginning to darken at the point of venom deposition. I sucked on the
finger until 8:35 a.m., when a pan of ice water that I had requested was
brought to me. No pain was felt except that caused by the ice. Fresh ice
was added as needed to keep the temperature low. By 9:30 a.m. the
finger had swollen and stiffened. At 10:00 a.m. the swelling had
progressed to the index finger and back of the hand. I experienced
difficulty in opening and closing the hand. Blood oozed slowly from the
incision. A dull ache persisted and about every two to four minutes a
sharp throb could be felt until nearly 11:00 a.m., when the pain
diminished. The rate and intensity of throbbing increased whenever the
hand was removed from the ice bath for more than a few seconds. Although
only the hand was immersed, the entire forearm was cold. Pain was felt
along the lymphatics on top of the arm when it was touched, and by 1:00
p.m. a slight pain could be felt in the armpit. Since swelling and pain
were almost nonexistent by 2:00 p.m., I was permitted to leave. After
walking to a nearby building, I again felt a burning sensation as the
hand warmed. I made another ice bath and again immersed the hand in it
until 4:10 p.m., at which time it was removed from the water. The pain
and swelling began anew, and the hand was placed back in an ice bath
from 5:30 p.m. until about 7:30 p.m. At this time cryotherapy was
discontinued. From 10:00 p.m. to 12:00 midnight my legs twitched
periodically, and pain could be felt in both armpits. A slight
difficulty in breathing also was experienced for a short time. The acute
pain and burning sensation remained in the finger until the following
morning, but swelling progressed only as far as the wrist. The only
discomfort that day was in the finger. The tip was darkened, the entire
first digit red and feverish, and the lymphatics still painful when
touched. By the third day the swelling had regressed. The incision
itself was the main cause of discomfort, and the soreness at the site of
the bite persisted for at least four days.
Although the L-C method of snakebite treatment has been vigorously
attacked by many, there is still need of much more data before it
can be unequivocally condemned or praised. It was preferred in the
treatment of this bite because: I knew that envenomation was minimal
and that there would be no need for antivenin; only one fang of a
snake less than one foot long had entered the tip of the finger; the
snake had bitten three frogs in the previous two days and had
possibly used up a considerable amount of its venom; the venom was
deposited at such a shallow depth that at least a portion of it
could be removed by suction; and the wound bled freely even before
suction was applied. The ice water was uncomfortably cold but was
not cold enough to cause frostbite, a major objection to the L-C
method. Ideally, fresh ice should be added little by little to
replace that which is melting, and the immersed area should be
protected from the water by a plastic bag. Pain and swelling can be
minimized by cryotherapy, but I would recommend its use only in
cases of mild poisoning such as the one described herein.
Snakebite in the United States
Many estimates have been made of the number of bites of poisonous snakes
that occur annually in the United States. The occurrence of poisonous
snakebite has been nearly as badly underestimated as fatal results of
their envenomations have been overrated. For important data on number of
persons bitten by poisonous snakes in the United States, see the
following: Allen and Swindell (1948:15); Githens (1935:172); Klauber
(1956:811); Parrish (1963); Sowder and Gehres (1963:973); Stimson and
Engelhardt (1960:153); Swaroop and Grab (1956:441); Swartzwelder
(1950:579); Willson (1908:530); and Wood (1954b:937).
Judging from estimates made in several states, the number of poisonous
snakebites in the United States would be about 5000 per year. In the
region where the cottonmouth occurs there are approximately 2000 persons
bitten annually by poisonous snakes. Of these approximately 39 per cent
are copperhead bites, 30 per cent each are cottonmouth and rattlesnake
bites, and I per cent are coral snake bites. These percentages vary
considerably from place to place, because of the distribution and
abundance of the eight species of poisonous snakes whose ranges overlap
that of the cottonmouth.
According to Parrish (1963), about 14 people die of snakebite each year
in the United States. Of these deaths, about 6.6 per cent are
attributable to cottonmouths, 77.0 per cent to rattlesnakes, and 1.6 per
cent to coral snakes; 14.8 per cent are unidentified. Almost half of the
fatalities are in persons less than 20 years of age, the high mortality
rate being partially due to the greater ratio of venom to body weight.
SUMMARY
In my study, 306 living and preserved cottonmouths were examined. This
species occurs throughout the coastal plains of the southeastern United
States, usually at altitudes of less than 500 feet but occasionally up
to altitudes of more than 2000 feet.
Two subspecies are recognized: the eastern cottonmouth, _A. p.
piscivorus_, occurring from extreme eastern Mississippi to southeastern
Virginia and Florida; and the western cottonmouth, _A. p. leucostoma_,
occurring from eastern Mississippi northward to southern Illinois and
Missouri and westward to central Texas. Intergradation occurs in eastern
Mississippi.
The northern edge of the range is probably limited by low temperatures
in winter, and the western edge by lack of available habitat resulting
from insufficient precipitation. Old records of occurrence indicate that
the range has decreased in the last 100 years. The species inhabits
mostly areas where water is found, but at times wanders a mile or more
from the nearest water.
The ground color is predominantly a brown, but varies from a
brownish-green to almost black with a pattern of 10 to 17 irregular
bands of a darker shade of brown. The pattern is better defined in the
eastern subspecies than in the western.
The scutellation resembles that of other species of _Agkistrodon_. In
the specimens examined supralabials ranged from 7 to 9, and infralabials
from 8 to 12. The number of dorsal scale rows on the neck, at mid-body,
and immediately anterior to the anus is relatively constant at 27-25-21,
respectively. Ventral scales of 34 males averaged 134.4 (128 to 139),
and those of 48 females 133.5 (128 to 137). The number of caudal scales
showed some degree of sexual dimorphism; the average was 45.4 (41 to 50)
in 34 males and 42.6 (39 to 49) in 44 females. In general, caudal scales
on the basal half of the tail are undivided, whereas those on the distal
half are divided. No marked geographical variation was found in any
scale character.
The poison fangs vary in length from 1.3 per cent of snout-vent length
in juveniles to 1.0 per cent in large adults. Fangs of captive
cottonmouths were shed and replaced at intervals of about 21 days, but
the interval was variable. Relationships in distance between the base of
fangs and between fang punctures in an actual bite indicate that
examination of the wound does not provide a good basis for judging
accurately the size of the snake that inflicted the bite.
In general, females less than 450 millimeters in snout-vent length were
juveniles; those more than 450 millimeters were classified as post
partum or reproductive on the basis of sizes of ovarian follicles. Since
about half the adult females were fecund, it was concluded that a
biennial reproductive cycle occurs in this species. An annual cycle may
occur in areas where temperature permits year-round activity. It was
estimated that females become sexually mature at an age of approximately
two and one-half years. Mating is probably most concentrated in early
spring at about the time when females ovulate, but copulation is not a
stimulus for ovulation. Sperm retention and delayed fertilization allow
young to be produced without copulation occurring in each breeding
season. The testes increase in size gradually rather than rapidly at
maturity or in each breeding season, but seasonal cycles in sperm
production occur.
The gestation period is three and one-half to four months. Determination
of sex in the embryos is possible by late June, because the hemipenes of
males are evaginated until the time of birth. Parturition generally
occurs in August or September, but captivity may delay birth for a month
or more. From one to 16 young per litter are born, depending on size of
the mother and other factors; but the average is between six and seven.
Mortality rate at birth is high in captive individuals but has not been
determined in natural populations. The sex ratio in embryos and adults
examined revealed about 53 per cent females. Because sufficient
information on population composition is not available, an estimate of
the percentage of adults in a natural population was based upon the
number found in my study. The reproductive potential was estimated from
these figures.
Normal young at birth are 230 to 240 millimeters in snout-vent length,
but their size is influenced by the condition of the mother. Comparison
of newborn young with those captured in spring indicates that little
growth occurs during winter. Early growth is largely dependent upon
feeding before winter quiescence.
The umbilical cord is broken at birth and the navel closes within a few
days, but the scar remains throughout life. Sexual dimorphism in the
position of the scar is characteristic of some snakes but is minimal in
cottonmouths.
In those snakes more than 700 millimeters in length, males outnumber
females three to one. The maximum age of cottonmouths in nature is
unknown, but one has been kept in captivity for more than 18 years.
Allometric growth is striking in cottonmouths. The head and tail are
proportionately longer in young individuals than in adults; and in males
the tail is, on the average, slightly longer than in females of the same
size.
Shedding of the skin provides for growth and wear in snakes. The young
shed within a few days after birth and generally shed more frequently
than adults. Frequency of shedding depends mostly on amount of food
consumed, and there is some evidence that injuries on the head and neck
increase the frequency of shedding. Before shedding, the eyes become
cloudy for about five and one-half days, then clear up again for about
four days before the skin is shed.
The food of cottonmouths consists mainly of small vertebrates and
occasionally invertebrates that are found near water. Fish, amphibians,
and reptiles make up nearly 70 per cent of the diet. Carrion is also
eaten and cannibalism occurs occasionally. Food is obtained by lying in
ambush or by active searching. The young are known to lure their prey
within striking range by waving their yellow tails in a manner
suggestive of writhing grubs. The method of obtaining prey differs
according to the kind of prey. Generally, cottonmouths retain their hold
on fish or frogs but release mice and larger prey after delivering a
bite.
The major causes of mortality of cottonmouths are obscure. Predators are
known to include alligators, indigo snakes, king-snakes, largemouth
bass, and blue herons; there are probably numerous others. Heavy
parasitic infestations were found among the snakes examined. Snake
mites, _Ophionyssus natricus_, became increasingly abundant on almost
all captive snakes in April and May of 1963. Lung flukes (_Ochetosoma_
sp.) were in 16 of 20 captive snakes, and many preserved specimens
contained nematodes (_Kalicephalus_ sp.) in the stomach and/or tapeworms
(_Ophiotaenia_ sp.) in the intestine. Although parasitic infestation
causes discomfort and may lower resistance to other detrimental factors,
it is difficult to attribute death to the effect of any particular kind
of parasite. Miscellaneous causes of death of some captive snakes also
were discussed.
The maximal body temperatures tolerated by four cottonmouths were
between 38 deg. and 40 deg. C., but a temperature of 38 deg. was lethal to a fifth
individual. Cottonmouths have been found on occasion when other snakes
were inactive because of low temperatures, but minimal temperatures
tolerated by this species are not known. The annual cycle of activity is
dependent upon temperature and thus varies from north to south.
Cottonmouths generally migrate inland in autumn, usually to dry forested
hillsides, where they den along with other species of snakes. After a
few warm days in spring they migrate back to the water's edge. The diel
activity cycle likewise depends upon temperatures but is influenced by
other factors as well. In spring and autumn, the snakes are active
mostly on warm, sunny days, whereas in summer they are active mostly at
night. In order to maintain adequate internal temperatures, much time is
spent basking mostly in a characteristic flat, resting coil either
beside a body of water or above water on limbs of dead trees. In this
position the snake is ready either for a short strike or a hasty
getaway.
Juveniles appear particularly aggressive and strike repeatedly when
approached, a behavioral pattern definitely favoring survival. Adults
vary in disposition, usually appearing sluggish and lazy, but they are
capable of striking rapidly when disturbed. The typical threat display
consists of lying in a coiled position with the mouth opened widely,
exposing the white interior, and with the tail vibrating rapidly. The
striking posture resembles the resting coil except that the anterior
part of the body is raised off the ground and the mouth is sometimes
opened. Musk is often ejected in a fine spray from glands in the tail as
a further defensive action.
"Head bobbing," more properly described as spastic contractions of the
body, was observed in captives when food was introduced into a cage
containing several individuals or when one of the snakes was returned to
the cage after being handled. Reports in the literature also have
connected these jerking movements with courtship. The response appears
to be elicited whenever a nervous state is recognized in another
individual and may serve to protect the jerking individual from
aggressive advances of the former.
The relatively heavy appearance of the body, sluggish habits, and
cryptic coloration are correlated with the development of venom and
fangs. The poison apparatus has developed primarily as a means of
causing rapid death in prey and secondarily, perhaps, to begin the
digestion of small animals that are the usual prey, but it is also
important as a defensive device. The venom contains at least eight
constituents that aid in its action on prey. Toxicity of the venom is
difficult to determine because of numerous variables, but cottonmouth
venom is generally believed to be less potent than that of most
rattlesnakes and more potent than that of the copperhead. Snakes in
general are more resistant to snake venoms than other vertebrates of
similar size, but there is no immunity even to their own venom.
About ten per cent of the approximately 5000 bites of poisonous snakes
per year in the United States are attributable to cottonmouths, and
about seven per cent of the approximately 14 deaths per year are caused
by cottonmouths.
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