The Venomous Snakes of Panama
by Norman W. Elton, M.D.
Chief, Board of Health Laboratory, Gorgas Hospital
Published by the Safety Branch
Canal Zone Government-Panama Canal Company

If one does not fear lightning one need have no fear of poisonous snakes, for it has repeatedly been demonstrated statistically that one's chances of dying from snakebite are not greater than those of being struck by a bolt of lightning.  Furthermore, the mortality among people actually bitten by poisonous snakes in Central America in Clark's Statistics is less than 10 percent.  This unusually low mortality in the tropics is readily understandable because our snakes are generally well-fed and do not hibernate.   These two factors tend to decrease the potency of their venom.

The commonest situation likely to result in being struck by a poisonous snake is an encounter with one that has just swallowed a meal (a lizard, a rodent, a bird) and, having failed to find cover after its night of successful hunting is so distended with its food ball that its belly plates are spread apart, and it is unable to move except with great difficulty.  This snake will strike in self-defense when molested.  However, in killing and swallowing its meal it has used up most of its venom, and for several days the refill in its poison glands will be very dilute and of low toxicity. It is, therefore, most reassuring to note that the offending snake is distended with a food ball, for the prognosis is then very favorable.

Most of the bites, as Clark has shown, involve the foot and ankle and the hand and wrist.   The protective coloring of many snakes may result in a bite on the buttocks, unless one is very observant at times.  The foot and ankle bites occur because vipers strike very low (even the King Cobra strikes the elephant on the toe -- although the cobra is not a viper -- because it "bows" from its "stand" to strike).  The hand and wrist bites are incurred largely in climbing a slope, when the snake is located on the higher ground.

As a rule poisonous snakes do their best to get out of the way of the traveler in the bush.  Exceptions occur in the case of the food-laden one which cannot get out of the way, and also, unfortunately, in the case of the pregnant female during the spring breeding season, which, laden with young or eggs, has found difficulty in obtaining food, with the result that her venom has become highly concentrated from enforced starvation.   Being unable to cruise about, she becomes highly defensive and quite aggressive -- in short, really "muy malo."  Bites from long-starved snakes are very serious and usually fatal.

In going into the bush it is a cardinal rule not to travel alone.  Accidents can happen, as well as snakebites, and groups should never comprise less than three or four individuals in a party.  It is a well known jungle axiom that "when troops move in, snakes move out."  Natives, traveling alone and poorly shod, are the principal victims of snake bites.  Most of them, when traveling this way carry a shotgun, if they have one, for such encounters.

When a jungle camp is occupied for any length of time, food waste will attract rodents, and rodents will attract snakes.  Since snakes hunt at night, some precautions will be advisable.  For example, before putting one's foot outside of one's wickiup, spot the ground with a flashlight first, just to make sure the coast is clear.  When the time comes to break camp, in handling boxes or piles of supplies take care to note whether or not a food-laden snake may be resting under cover of the material being moved trying to keep out of the way while digesting its meal.

The treatment of snakebite in an emergency situation can be made quite simple and effective.  In the first place, the snake would be identified, caught, and at least its head with 2 inches of its neck should be secured for proper identification in case it is considered advisable to administer antivenin later on.  If the snake is not poisonous, treat the wound as a potentially infected abrasion or laceration, preferably by immersion for 20 to 30 minutes in hot soapy water.  If the snake is poisonous, then apply mouth suction at once to the region of the fang holes, encompassing the area widely with the teeth and lips and milking the contents of the fang channels in much the same manner as a suckling infant at the breast.  The mechanism involves gentle massage with the teeth as well as suction.  As an adjunct a tourniquet should be applied to the upper arm or thigh, but tight enough to shut off only the veins, and not tight enough to stop the pulse in the wrist or ankle.  This will block the venous and lymphatic absorption of the venom and by keeping the arterial blood pressure sustained, will tend to flush out the venom through the fang channels.

There are very good reasons why incisions at the site of the fang punctures should not be attempted.  Viper fangs are long, curved and hollow, and the opening through which the venom is ejected is close to the tip of each fang.  The venom emitted from the fang will not be in the vicinity of the puncture holes on the skin, but will be deep in the tissues and off to one side, depending on the direction from which the strike was made.  If these fang channels are left intact venom can be drawn out by the mouth suction method to the skin surface without further absorption, but if the fang channel has been interrupted by incision, not only will the withdrawal of the venom be made more difficult, but also fresh raw tissue surface area will be exposed to facilitate additional damage and absorption without in any way assisting in the removal of the venom from the deep pockets under the skin.

The mouth method of suction and "milking" is far superior to any cup suction.   Most cups have too narrow a diameter and not only do not include both holds, if both fangs pierce the skin, but tend to compress the fang channels, when they run in oblique direction,and block the outflow of the ooze from the deep venom pockets.

Venom when swallowed is harmless.  If one's mouth is in good condition, without abrasions, open ulcers, or bleeding gums, mouth suction will not harm the person performing it.  However, if there is any apprehension relative to the possibility of absorption of venom through a break in the mucous membranes of the mouth, then a sheet of thin late rubber should be placed over the sin before applying the mouth suction in order to  protect the operator.  This will not impair the efficacy of the treatment and a rubber sheet, or material from which it can quickly be made, should be carried as a party of the necessary individual equipment taken on jungle trips.  It is easily carried in a waterproof matchbox.

Before undertaking a more detailed discussion of the several species of poisonous snakes of Panama, let us recapitulate the procedure to be observed in case of snake bite.

1.  Prevention of Snake Bite:

a.  Do not travel alone in the bush; a companion may see the snake that you do not notice
.
b.  Be well shod.  At least do not wear low shoes.  Tuck trousers into boots and have trousers loose and baggy.

c.  Be watchful when using your hands in climbing or in clearing brush.  The native who knows how to use a machete, has a bent stick in his left hand to hold branches and small vegetation prior to clipping it with his machete.

d.  When you see a snake, freeze in your tracks until you can estimate the situation.   The snake will not attack you, since he will be as much surprised and disturbed as you are, and the chances will be 4 to 1 that he is a nonpoisonous type.

e.  If alone and proceeding through snake country, make a lot of noise to give the snakes a chance to get out of your way.

f.  Carry in your equipment a rubber sheet (thin late) and a piece of rubber tubing for use as a tourniquet.

g.  Be especially watchful at night.  This is when the hungry snakes are hunting rodents.  They will not be hunting you, but there might be a misunderstanding.

2.  Action in Case of Snake Bite:

a.  Identify snake.  Is it a poisonous species? Look for the snake in the immediate vicinity as snakes with food balls cannot go far.  Have someone in the party get the snake if you have a burlap bag to put it in.  Otherwise obtain its head and about 2 inches of neck for later identification.  The severed head of a poisonous snake can still produce a bite, so handle it carefully.  Boa bites are razor-like, but quite clean, and require the same treatment as ordinary wounds.

b.  If the snake is of a poisonous species, find out if it has a food ball.   If it has, then the person bitten has much less to worry about, since the venom will be of low toxicity.

c.  While someone is taking care of the snake, the person bitten can apply his own mouth suction, if it is an accessible hand or wrist bite.  If it is an ankle or food bite, someone else in the party will have to be the operator.  A tourniquet on the upper arm or thigh, not tight enough to stop the pulse, should also be applied.   There may be only one fang hole, since the snake may have shed one of its fangs before the replacement fang was ready for use.

d. Take the patient without delay to the nearest medical installation, but keep up the mouth suction intermittently on the way.  Release the tourniquet for a couple of minutes every 20 to 30 minutes to prevent damage from the tourniquet itself.   Present the snake, or its head and neck, to the doctor for proper identification, with information as to the presence or absence of a food ball.

Regional snake faunas of the geographic divisions of the world vary in the different localities.  In each area the principal effort should be directed toward acquiring a familiarity with the poisonous species, since they are usually less abundant than the others and of ore importance to man.  They are also better known by local or common names than the more abundant and varied relatively harmless species.

In our part of the world there are three main families of poisonous snakes; namely, the pit vipers, the corals, and the sea snakes.

Only in the Western Hemisphere do the vipers all have pits.  This is a recess on the outside of the upper jaw between the nostril and the eye, which as Harold Trapido points out (based on the work of Noble and Schmidt), is a temperature-detecting organ that provokes their strike at the warm-blooded animals they seek as prey when close enough to detect the body warmth of the passing victim.  Trapido also believes that the pit-like structures along the side of the lower jaws of the constrictors (boids) may perform the same function.  Even though pit vipers are blinded with blackened collodion and their tongues removed, they will strike at an electric light bulb covered with opaque black material only with the filament is hot.

Vipers have long retractile, hollow, curved fangs situated in the front of their upper jaws.  These fangs are thrown down and forward when in striking position, and are concave to the rear.  When the strike is made and the fangs pierce the victim, there may be a slight tug backward, and the constriction of the venom glands ejects the venom out of the hole in the fang just above the point and to the front, where a small space in the victim's tissues has been made by the slight backward tug of the fang.  Viper fangs may attain a length of 1 1/4 inches n the large fer-de-lance or bushmaster.

Accurate identification of poisonous snakes involves a careful study of each species and of the individual variations within the species.  The young are often different from the adults.  There is hardly any rule of thumb that can be applied indiscriminately.   Facial pits are of considerable importance, especially in the Western Hemisphere, for recognition of the vipers, but many of the Old world vipers lack pits.  The slit pupil of the eye can be demonstrated also in  harmless snakes, ad is a group characteristic of those with nocturnal habits.

Bushmasters have a double row of plates under the tail, though in other venomous snakes this row of plates is often single.  Snakes that have new coats after shedding look quite different from others that are about to shed their old skin.

The pit vipers of Central America consist of seven main species: the fer-de-lance, the bushmaster, the tree vipers, the hog-nosed vipers, the mano-de-piedra, Godman's viper, and the tropical rattlesnake.

The Fer-De-Lance

The fer-de-lance, a member of the Trimeresurus family, is also known as the terciopelo ("velvet skin"), the barba amarilla ("yellow beard"), and the equis (because of the -like design of its body markings).  This is a snake, which although found in the jungle up to 2,000 feet in altitude, commonly frequents lowland plantations in search of the rodents that live on the abundance of fruits.  In the plantations the "equis" has come to be regarded as a benefactor of man, because of its controlling effect on the rodent population.  This snake is slender, dark, often black, with light colored somewhat light-yellowish to light-gray -like designs on its back, and averages, when fully grown, about 5 feet in length, rarely attaining 6 feet.   Its head is lancet-shaped, whence it has derived the name "fer-de-lance."   The females are viviparous, giving birth to some 45 to 70 lively and very aggressive youngsters in each litter.  These newly born snakes are just as dangerous as their parents, for their food (moths and insects) is hard to get, their competition among themselves is keen and their venom concentrated.  Because of the trouble they have in feeding they are liable to be encountered still active in bushes and grass after sunup, a time when most vipers seek cover.  This was apparently the first   lancet-headed new world snake observed by the European settlers, and for a long time was thought to exist only on the island of Martinique, and in South America.   Later it was found to have a much greater range, including all of Central America.   Other species of lancet-headed vipers were soon discovered.

Baby fer-de-lance are lighter in body color, and somewhat difficult to distinguish from some of the harmless snakes of the same size.  This is why most of the people who have been in the bush always regard such small snakes with suspicion, and consider many innocuous types as dangerous "equis" until proven otherwise.

The fer-de-lance has come to be regarded as the most dangerous snake in the Panamanian jungles, chiefly because it is the commonest of the vipers.  The speed of its strike it so fast that the eye can hardly follow it, although its striking range is very short (6 to 10 inches).  It is said that the mongoose which invariably masters the cobra, has only a 50-50 chance with the fer-de-lance.

As with most snakes, the sex of the "equis" is hard to determine without dissection.  Not infrequently in the spring of the year a "well-fed" snake taken into captivity may surprise its keepers by giving birth to young in great numbers.   This happened once in a scientific institution in Panama, for one morning it was discovered with dismay that the "well-fed" snake, a fer-de-lance, had grown very thin during the night, and the vicinity of the cage was swarming with about three score lively little "equis" with a ravenous appetite.  A real snake hunt ensued.

A frequent heckler's question asked of a person expounding about snakes may be "How do you tell the males from the females?"  Lyle Womack has a good answer to that one in the reply "That, my friend, is a question of great importance to the snakes, but not so much concern to us."

The Bushmaster

This oval-headed, longest and heaviest viper of the American Tropics, averages about 7 feet in length, and would weigh about twice as much as a fer-de-lance of the same length.   Although specimens have been reported up to 14 feet in length, they have not yet been brought in here for confirmation.  It is the second largest poisonous snake in the world, second only to the king cobra, and frequents rocky forested country.  Its general body color is tan, with a black saddle-like pattern on its back.

Although a powerful snake, and much slower than the fer-de-lance, it must be handled carefully when captured, because its back is easily broken, and many valuable specimens have been spoiled in this fashion when taken alive.  The bushmaster does not do well in captivity, invariably dying in a short time, and seldom will it be found in any zoo.

The scientific name of this snake is Lachesis Muta.  It is also known as the "verrugosa" or "warty one," and as the "cascabela muta" (silent rattle snake) because of the spine on the tip of its tail which may vibrate among dry leaves so as to simulate the sound of rattles when it is alerted or nervous.  It is also sometimes called "mapana."

Bushmasters lay eggs, about 10 to 14 at a time, and those that survive after the hawks, rodents, coati-mundis, and other predators of the jungle have eaten what they find, hatch into young snakes that immediately disappear underground, where they frequent the burrows of the rodents, living in turn on their young.

Apparently when they become too large to maneuver effectively in the burrows, they become terrestrial, but not until they have practically attained adult size.  Young bushmasters have seldom been captured or even seen beyond the egg stage.

It would seem appropriate to stress the rarity of the occasion when one will see a bushmaster.  Yet, I recall a day in 1943 when Dr. Clark was stressing this very point to a group of naval officers undergoing jungle training by Maj. Cresson H. Kearny, of the Panama Mobile Force, on the Madden Forest Highway.  That same afternoon Kearny took them off on a compass course cross-jungle from Las Cruces Trail, and they returned a couple of hours later with a live 7-foot bushmaster.  Unfortunately its back was broken and it died over the weekend.

This brings up the point of snake collecting.  Using a loop-on-a-pole catching device, the live snakes should be deposited in a good burlap bag.  Thus they may be carried satisfactorily and comfortably, preferably with the bag tied.  For some reason or other they cannot endure a horseback ride, frequently dying en route when carried in this manner, but they will survive an automobile ride.

Hog-Nosed Vipers

The small hog-nosed vipers of Panama are true pit vipers, definitely poisonous, and not related generically to their harmless namesake in the United States.

They are of two species:  (1) Trimeresurus lansbergii of the Pacific side and (2) Trimeresurus nasutus of the Atlantic side.  Their common names are patoca or tamaga.  They range in length from 12 to 18 inches.  The tipped-up nose of the Atlantic species is more prominent than that of its Pacific relative.   They are dark brown or black with faint brick red rhomboid markings on their backs.

As a ground snake of the sabanas more than of the forest, it is less apt to strike than the fer-de-lance, and few bites have been reported by these species.

Eyelash Snake - Tree Viper

Tree Vipers

There are three species of tree vipers, the commonest being Trimeresurus schlegelii (horned palm viper, eyelash snake, bocaraca, toboba de pestamas, oropel, or sleeping gough).  This is a small sometimes rather stocky, snake, 10 to 14 inches in length including its prehensile tail which enables it to live in trees and bushes, where it feeds principally on birds.

The drawing of its head hardly does it justice, for its expression is that of unmasked malice in pure form.  Their colors vary from olive green or butter yellow, with specks of black, to almost black with a pinkish pattern over the back, even in littermates.

Their prehensile tails and scales above the eye, standing out as small horns or eyelashes, make identification easy.  Common in cacao plantations, they may be encountered in the felling of trees and bushes.  Several were collected by the Mobile Force troops in the Pina area during the war.

Their venom spells instant death to birds.  Clark tells of seeing one strike a bird only a glancing blow.  The bird fell to the ground, and by the time it could be located and picked up it was stiff with rigor mortis.  Clark knows of only one instance of a workman being struck on the shoulder near the neck.  After some discussion at the time (facetiously) of where to apply a tourniquet for such a location, mouth suction was applied, and the man recovered uneventfully without specific treatment.

There are two other species of tree vipers, without eye-lashes, which so far have been found only at elevations of 4,000 to 6,000 feet.

One, Trimeresurus lateralis has light stripes along its sides, and the other, Trimeresurus nigroviridis  has powerdershot black specks scattered throughout the green body background.  they are about 18 to 30 inches long and both are green in color.

The "Jumping Snake"

This is another dart-headed snake, about 10 to 20 inches in length, with a very heavy body.  The body pattern resembles that of the bushmaster, but is of a double saddle and stirrup pattern in pairs at close intervals.

Its strike is so vigorous that it may stir up a cloud of dust as its short powerful body pulls away from the ground.  This is how it derives its common names, "jumping snake," "timbo," and "mano-de-piedra."

They are found in rocky elevated places; one large individual having recently been brought in from the East Ridge.  Its scientific name is Trimeresurus nummifer.

The Tropical Rattlesnake

The tropical rattler, Crotalus durisus, is by far the deadliest of all, but none have as yet been collected in Panama.  Only one is now a collector's item at the Board of Health Laboratory, and that was presented by Douglas March from his Honduras collection.  Its colors have long since faded out in formalin.

It is alleged to exist in the dry tablelands of the Provinces of Chiriqui and Veraguas, where it is zealously protected by the natives of the Bocas del Toro region. 

To these Indians the tropical rattler is a religious symbol and an economic asset, for, depending on its venom for obtaining their food, they make up a mixture of liver paste and venom which which to tip their hunting arrows and spears.

They allow no white intruders to enter their domain, or to molest their snakes.   Explorers in that area, once believed uninhabited, but now found by air observation to be under intensive cultivation, are no more welcome than were the Conquistadores; and to those Indians contemporary man is still as undesirable and treacherous as they by bitter experience to be characteristic of the Conquistador.

Godman's Viper

This is another small thick ground viper, black in color, and about 18 to 22 inches in length.  Natives say that they seldom strike a person, and there are no records of bites.  They have been found at about 4,000 feet elevation.

The Corals

I have hardly mentioned the coral snake up to this point.  The coral minds its own business, usually tolerates gentle handling if one is indiscreet enough to pick one up, and asks only to be let alone.

It would, however, be very dangerous to step on one inadvertently with bare fee, for it will resent being hurt.

It always reminded me of the easygoing cocker spaniel of the poisonous snake family.   Being a burrowing snake, few accidents have been caused by it.

There are about 11 recognized species of true corals in Panama, many of them very small, and not all tricolor.

The common true coral, ranging from 10 to 20 inches in length, is tricolor, and may be described as like a newspaper, "Black and while (sometimes yellow instead of white), and red all over."  The basic body color is coral red with black bands bordered by white (or yellow) at intervals.

The eye of the poisonous tricolor corals is very small, in contrast with the larger eye of the nonpoisonous tricolor false corals.

The coral's scientific name, as a member of the elapidae, is micrurus of the given species, such as Micrurus nigrocinctus, which is the one commonly seen.   It is also known as the harlequin snake.

The coral in Mexico is known as the "20-minute snake," for the victim is supposed to be a goner 20 minutes after being bitten by one.

However, the coral is not well-equipped for biting, and its fangs are short, grooved, and fixed, placed so far back in its upper jaw that it has to batter at its target fast and furiously, like a sideswiping trip hammer, before it can get a grip.  then, when it does get hold of a fold of skin, it hangs on like a bulldog and chews like a cobra to instill its venom.

It is capable of causing a serious bite only under such favorable circumstances.   Needless to say, since its fangs are so short, and its bite so superficial, incisions would hardly be indicated in treatment.  Regular snakebite technique, as outlined in Part I of this discussion, should suffice.

The Sea Snakes

In the Pacific, ranging from the shores of Panama to the Indian Ocean, there are some 50 species of sea snakes, from 1 to 3 feet in length.

These true reptiles do not molest man unless they happen to be caught in a net with a lot of fish, or are washed up on a beach, and handled.

Related to the corals, kraits and cobras, their venom is a highly potent neurotoxin.   Although they have often been seen washed up on the shore of the causeway leading to the attached islands of Naos, Culebra, Venado,and Flamenco, and on the beach of San Jose in the Perlas group, no one has ever yet been bitten by one in Panama.  Clark tells an amusing story of a trip he made down the coast.  There being only one panga to use for going ashore, he dove in and started to swim the 200 yards to the beach.   He had not been swimming long before the rest of the party on the boat began yelling at him and pointing to the water.  Thinking it some joke, he waved casually and continued swimming to the shore.  When he mounted the bank on the beach, they were still yelling and pointing to the water.  He then looked himself, and to his chagrin realized that he had swum through a school of thousands of sea snakes without ever feeling the touch of one of them.  "Well," he grunted, "They're just looking for shrimp and small fish to east."  But he didn't swim back to the boat to prove it.  These snakes have never been known to attack swimmers.

The common sea snake of the Panama coast is Pelamydrus platurus, a black snake with  orange patterns on the side and belly, having a tail vertically flattened like an eel or an oar blade.

It is at times exceedingly abundant in Panama Bay.  Length is about 12 to 24 inches.

The Nature of Snake Venom

Venom is actually a potent saliva derived from the parotid gland of the snake which, in man, is the salivary gland that becomes swollen when we have mumps.

The use of venom defensively is a secondary adaptation, for its primary use is to kill and digest the prey.  Hence a snake uses up most of its venom in killing and swallowing its victim.

Venoms are complex proteins of high toxicity and their mode of action is mainly of two and possibly three types:  one, an effect on red blood cells and the walls of blood vessels, causing dissolution of the red blood cells and hemorrhages from the damaged capillaries; another, acting on the nervous system, inducing paralysis of muscles, especially affecting those nerves that operate the muscles having to do with respiration; and a third consisting of a general digestant action on all tissues, especially after the local death of tissue resulting from the other effects.

Kenneth Vinton has pointed out that this digestant action of venom will actually operate favorable during suction treatment of snake bite by widening the fang channel and facilitating the outflow of tissue juice containing the venom from the site of injections.

Conclusion

An apology seems in order for my pretense at knowing something about snakes.  I have enjoyed an association with a number of outstanding naturalists,  physicians, and biologists during my periods of service in Panama, among whom the most stimulating has been Dr. Herbert C. Clark, and many of the ideas I have presented are really his.

My contribution rests mainly in the dissemination of this information during my service as Mobile Force Surgeon in 1942-1944, when I covered some 400 miles on foot on patrols, hikes, and inspection trips, and assisted Maj. Cressson H. Kearny in his work of preparing troops for operations in the jungles.

All who are interested in snakes in a scientific way, I should like to refer to a number of people who are far more expert than I, such as James Zetek, at the Barro Colorado Biological Area, Dr. G. B. Fairchild, and Dr. Harold Trapido, at Gorgas Memorial Laboratory, to Kenneth Vinton at the Canal Zone College and to the Museo Nacional, in Panama City, where there is an excellent collection.

Thanks to Bill Fall for contributing this article.

CZBrats
September 27, 1999

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