That Reptile Blog – Reptile, Amphibian and Exotic Pet Care and Information

The term “rear fanged” is applied to a variety of unrelated snakes that possess a venom-producing gland and 1-3 enlarged, grooved maxillary teeth in the rear of the mouth. We do not yet know how many species possess these venom-conducting teeth (“rear fangs”), but evidence indicates that snake venom evolved some 60 million years ago – before non-venomous snakes came into being. Therefore, all present day species may have evolved from venomous ancestors, and may possess at least the traces of venom glands. The rear-fanged snakebites I’ve dealt with in the course of my career have elicited only mild reactions. Some rear-fanged species, however, have caused fatalities – two very “famous” fatalities, in fact (please see below).

 

Snakes Best Kept in Zoos

As individual sensitivities and other factors can greatly affect one’s reaction to a bite, even “mildly venomous” species must be considered as potentially dangerous. A lifetime of experience as a zookeeper and herpetologist has taught me that it is impossible for a private snake owner to adequately prepare for or treat a venomous snakebite at home, or, prior to a bite, to arrange for treatment in a hospital.

 

Until we learn more about them, rear fanged snakes are best considered as suitable for display in zoos rather than private collections. Tentacled Snakes (Erpeton tentaculatum) and certain others may be an exception, but I advise consulting a herpetologist and an experienced medical doctor if you feel compelled to acquire a rear-fanged snake of any species.

 

 

 

Overview

Rear fanged snakes are classified in the huge family Colubridae (the “Typical Snakes”), but are not necessarily closely-related to one another. The term is applied to a variety of species that possess the venom-producing Duvernoy’s Gland. One, two, or three of the maxillary teeth in the rear of the mouth are enlarged and bear grooves on their front surfaces. Venom released by the Duvernoy’s Gland flows down these grooves and into a prey animal or foe. A period of “chewing”, in the manner of cobras and other Elapids, may be necessary in order to fully discharge the venom.

 

This method of introducing toxins into a wound is rather ineffective when compared to that employed by rattlesnakes and other Viperids. Also, many rear fanged species produce venom that is most or only effective against the specific animals upon which they feed. Therefore, not all present a threat to people.

 

However, much remains to be learned. For example, Boomslangs (Dispholidus typus) and Twig Snakes (Thelotornis kirtlandi) were not widely believed to be dangerous until each killed a prominent herpetologist! (I use “widely” because both were feared by local people).

 

Size

At an adult size of 8 inches, North and South America’s Crowned Snakes, (Tantilla spp.), are the smallest rear fanged species known.

 

Widely-distributed through much of Southeast Asia, the 7-foot-long Mangrove Snake (Boiga dendrophila), is the largest. This spectacular snake’s size and striking coloration render it much desired in the trade, and many are held in private collections. Those I’ve kept in zoos have remained high-strung and difficult to work with. Fatalities have not, as far as I know, been attributed to their bites, but large individuals can store up a substantial quantity of venom – I’d leave these beauties alone!

 

Diet

Many rear fanged snakes have evolved toxins that specifically target reptiles and amphibians, and may specialize in hunting lizards (Mexican Vine Snake, Oxybelis aenus), frogs and toads (Malagasy Giant Hog-Nosed Snake, Lioheterodon madagascariensis) or fish (Tentacled Snake, Erpeton tentaculatum).

 

Others, such as the Mangrove Snake (Boiga dendrophila), are generalists that consume a variety of creatures, including birds and mammals. The tiny Crowned Snakes, Tantilla spp., limit their diet to earthworms, centipedes, beetle grubs, and other invertebrates.

 

“Harmless Snakes” with Venom

Recent research has shown that 2,000 or more snake species, many considered “harmless”, likely produce true venom. Most do not have efficient rear fangs, and produce toxins that pose no danger to people, but this does point out the need for caution and research.

 

 

Further Reading

Venomous Snakebites: My Experiences and a New Study

The USA’s Most Dangerous Snake?

 

Working with Spitting Cobras has been a fascinating, if sometimes un-nerving, experience. In addition to being able to deliver venom via biting or ejection through the air, Spitting Cobras also have the alertness and speed that is typical of nearly all the world’s 353 Elapid species. On two occasions, I’ve had to re-capture a total of 6 escaped Red Spitting Cobras (Naja pallida) – once because a man helped his little son to kick in the glass of an exhibit at the Bronx Zoo! (please see article linked below) But despite these incidents, and decades of working closely with related species, the only venom to wind up in my eyes came not from a Spitter, but rather courtesy of a species that “cannot spit” – the Western Diamondback Rattlesnake (Crotalus atrox).

 

 

Illegal Rattlesnakes: Live and Cooked

Most of the obvious risks associated with venomous snake care are easy to avoid (in a reputable zoo, that is…one cannot properly prepare for a bite delivered by a snake in a private collection). When working with Spitting Cobras, for example, safety glasses are always worn. Emergencies occur, of course, and then you must sometimes make do without. In the escape mentioned earlier, for example, I arrived on the scene not knowing that Red Spitting Cobras were involved, and I had to immediately evacuate visitors, many of whom were children, from the area.

 

But, as in most fields, the greatest dangers arise from unexpected situations – those that we don’t imagine or believe can happen. This was the case one day when I was in a Bronx Zoo holding area, checking on some newly-arrived Western Diamondback Rattlesnakes. The snakes had been confiscated the night before, in a store in NYC, of all places. Several police officers had entered following a report of a burglary, and found snakes instead of criminals. The snakes, mainly Western Diamondbacks, were being held in a variety of slip-shod containers; several dead individuals were in cooking pots, alcoholic drinks, and “medicines”. As usual, the Bronx Zoo was summoned.

 

“Hey…Rattlesnakes Can’t Spit”

Co-workers and I had installed the snakes in screen-topped aquariums in an isolation room at the zoo’s Reptile House. As is dictated by protocol (and common sense!), I was careful not to lean on any screen tops as I checked the animals. All were highly agitated. Unable to see one individual clearly through the tank’s glass side, I peered down into the screen top. The snake struck at the top, and I instantly felt a splash of liquid in both eyes.

 

The standard wisdom is that only Spitting Cobra venom can cause eye damage. In the rare event that another type of venom enters the eye, it needs merely to be washed out; a follow-up with a doctor, to assure that an infection does not take hold, should follow. But this incident was unique for two reasons. First, the force of the snake’s strike against the screening had propelled the venom into my eyes. Second, I had just returned to work following a cornea transplant. There were numerous stitches in my eye, and they were not all that stable.

 

I felt a stinging sensation (which is not typical for other than Spitting Cobra venom) and thought that perhaps the venom had seeped under my cornea through the stitches. I wondered if the transplant could be ruined, and if I might suffer a typical envenomation as well, once the venom moved further along in my body.

 

Just When You Thought You Had Seen Everything…

The Bronx Zoo’s snakebite protocol relies upon the NYC Police Department for transport to the hospital. Fortunately, several NYPD Officers are always on the grounds. I was on friendly terms with all – one, in fact, was a former BZ animal keeper, and all were top-notch. It’s hard to surprise an officer who’s spent some time in the Bronx, but I did a good job that day! In less time than I could imagine, I was at Jacobi Hospital being attended to by a young doctor who, after some time in a busy Bronx emergency room, thought he had seen it all!

 

All went smoothly, and I suffered no symptoms of envenomation. It would have been interesting to learn if the venom had entered my body via a cornea stitch, but in those years Bronx hospitals were unbelievably busy (often with unbelievable, at least to me, cases) and there was no time for speculation or experimentation – I was shuttled out as quickly as I’d arrived!

 

 

Further Reading

A Close Call with a King Cobra

Snake Escapes!

 

Big and bold, the Cottonmouth or Water Moccasin is one of the most frequently-encountered of the USA’s venomous snakes. Stories of its alleged ferocity abound, and many folks living within its range are convinced that it goes out of its way to attack people. I’ve had the chance to work with this impressive serpent at the Bronx and Staten Island Zoos (Note: venomous snakes should never be kept in private collections), and to observe it in the wild, and have found its actual habits to be far more interesting than the supposed ones! From scavenging road-killed pigs to turning up in areas far north of where most people “expect” it, the Cottonmouth is full of surprises. Today I’ll focus on the natural history and captive care of the Eastern Cottonmouth (Agkistrodon piscivorous picivorous), with some comments on the 2 related subspecies.

 

Description

Most Eastern Cottonmouths are olive to dark brown in color, and are patterned with irregular, dark cross-bands. However, nearly-black, pattern-less individuals are common, and hybrids (which vary in appearance) occur where its range overlaps with that of the Florida and Western Cottonmouths.

They are stoutly built, and this makes adults appear larger than their actual size. Most average 3 to 5 feet in length, but occasional “giants” turn up. The published record length is 6 feet, 2 inches…but there’s no shortage of people who will claim to have seen, or even killed, Cottonmouths twice or three times as large (note – they haven’t!).

 

Several of the larger, non-venomous water snakes of the American Southeast are often confused with the Cottonmouth, as they are superficially similar in appearance and share the same habitat. And if you’ve ever tried catching a large Brown or Florida Green Watersnake, you’ll understand why most “non-herpers” give these irascible brutes as wide a berth as they do Cottonmouths!

 

The Cottonmouth is classified in the family Viperidae, and is most closely-related to the Copperheads and various Cantils of Mexico and Central America.

 

Range

The Eastern Cottonmouth is found from southeastern Virginia to eastern Alabama and Georgia. I grew up associating Cottonmouths with Florida’s swamps and canals, and indeed it is there that the Florida Cottonmouth, (A. p. conanti) thrives in good numbers. I was surprised to learn, however, that the Western Cottonmouth(A. p. leucostoma)ranges much further north than I expected – to southern Illinois and eastern Missouri.

 

Habitat

Cottonmouths are typically found in and along slow-moving bodies of water such as swamps, marshes, canals, rice fields, ponds and weedy lakes. However, they will forage in fields, open woodlands and around farms, often far from water. Individuals in many populations hunt mainly by night, especially during the summer, but they bask in the daytime.

 

In the northern sections of their range, Cottonmouths hibernate in subterranean dens on land, often on hillsides far from water. Hibernation sites may be shared with copperheads, rattlesnakes, water snakes, ratsnakes and other species.

 

Status

Cottonmouths can be quite common in suitable habitat and in protected areas such as the Everglades, but are threatened in some regions by wetland drainage. Basking Cottonmouths are said to be used for “target practice” in some places…not much of a challenge, given their size and immobility when basking, I imagine!

 

Longevity

Zoo specimens have reached at least age 24; several under my care were in their late teens, and still full of spunk. Longevity in the wild has not been well-documented, as far as I know.

 

Reproduction

In most populations,females breed every-other-year, usually in August and September. The young, 1-16 in number, are born alive and are 7-13 inches in length. They are reddish-brown and vividly marked, and use their bright yellow tail tips to lure frogs, lizards, and other prey. Sexual maturity is reached in 3-4 years.

 

Diet

Cottonmouths take a wider range of prey than do most other snakes, and even scavenge road-kills. I was once very surprised to read a journal note (Herpetologica?) describing a large individual consuming chunks of fat from a dead pig!

 

The usual diet is extremely varied, and may include catfish, bream, eels and other fish, sirens, amphiumas and other salamanders, frogs, hatchling alligators, small turtles, lizards, snakes, ducks and other birds, and mammals such as rice rats, muskrats and voles.

 

I once housed a colony of Green Anoles with a pair of Cottonmouths at the Bronx Zoo. Whenever I tossed roaches or crickets in for the lizards, the Cottonmouths would move about in an apparent search for food. I’m wondering if youngsters consume insects as well; the closely-related Copperhead has been observed feeding upon cicadas and grasshoppers.

 

Cottonmouths under my care were fed minnows, shiners, trout, goldfish, mice and rats; I’ve always meant to try crayfish, but unfortunately did not. Like many fish-eating snakes, they seemed perpetually hungry. The opening of their exhibit door, with or without the scent of food, generally elicited a mad rush forward. All those I’ve kept adjusted well to captivity – thrusting them away with a snake hook did nothing to damper their desire to feed!

 

Additional Information

The name “Cottonmouth” arose from this species’ threat display – when cornered, it throws back its head and gapes widely to expose the cottony-white interior of the mouth. If this fails to dissuade the intruder, the snake strikes repeatedly. Basking animals usually drop into the water and swim away, either below or at the surface, when disturbed.

 

Classification of Cottonmouths and other Vipers

Cottonmouths and their relatives, collectively known as “pit vipers”, are placed in the family Viperidae and subfamily Crotalinae, along with palm vipers, rattlesnakes, copperheads and related species. They are considered to be the most advanced, or highly evolved, of all snakes.

 

Crotalids, or pit-vipers, possess a sophisticated sensory organ (the “pit”) that detects the infra-red rays produced by birds and mammals. Located between the eye and nostril, this organ is far more sensitive than the heat receptors that have evolved among the boas and pythons. The arrangement of the heat receptors within the pit viper’s sensory organs are replicated in the brain and integrated with visual information received there. The pit may thus be considered more of an “imaging device” than mere heat receptor, and likely provides detailed information concerning the size and shape, as well as location, of warm-blooded animals. Aided by these unique organs, pit vipers are able to hunt and escape predators even in complete darkness.

 

Vipers possess long, hinged fangs that fold back against the roof of the mouth when not in use. Venom is injected with a single bite, in the manner of a hypodermic needle. The snake then retires and allows the prey to run off, and follows its scent trail once the stricken animal has expired. This strategy spares vipers the injuries that can be inflicted by prey animals upon snakes such as cobras, which must hold on while injecting venom. When attacking frogs, fish and other relatively benign prey, however, Cottonmouths hold onto the animal after striking.

 

 

Further Reading

The World’s Largest Rattlesnake

Keeping Watersnakes

 

 

As the weather warms, snake identification requests are becoming more common on my blog. Of most concern to those unfamiliar with reptiles is the possibility of encountering venomous species. Often, a fleeting glance is all that has been had, and identification proves very difficult. So today I’d like to direct folks to some useful online and published resources that are useful to review before a snake is sighted as well as after. Of course, please continue to post your questions and observations as well…some species are quite distinctive, and other times the location of the sighting or certain behaviors can be used to narrow down the possibilities.

 

I’ve been involved with snake bite response efforts through the Bronx Zoo and other organizations for most of my working life, and have learned that, in the USA, most bites occur when people disturb snakes or keep venomous species as “pets”. Worldwide, the situation is different, with an astonishing number of people being bitten, often fatally, in the course of their daily activities (please see the article linked under “Further Reading”). Please heed the cautions provided below.

 

Note: The following information should not be used to determine if a snake is safe to handle or approach, nor should any other printed guideline. Aberrations in color or pattern, injuries, hybridization and other factors – including the very real possibility of escaped non-native “pets” – can render identification impossible to all but a well-seasoned expert. Concerning exotic escapees, bear in mind that we still have much to learn…and that two prominent herpetologists were killed by snakes thought to be relatively harmless! Also, please note that the flood of both accurate and outright ridiculous information on the internet sometimes inspires a feeling of false confidence in the inexperienced, and gives credence to the old saying “A little knowledge is a dangerous thing”!

 

The primary resources listed here are based on Florida’s venomous snakes. However, Florida is home to representatives of each type native to the USA, and the state’s museums and universities have a long history of fine educational efforts in this area. Specifics as to species found in other parts of the country will vary…please see the notes on field guides, and post below if you would like a guide to the species present in your state or region.

 

University of Florida Website

Prepared by the Department of Wildlife Ecology and Conservation, Dealing with Snakes – IS IT VENOMOUS? provides a great overview of the 4 general types of venomous snakes found in the USA – copperheads, rattlesnakes, cottonmouths and coral snakes.   The most easily-recognizable characteristics of each are highlighted, which makes it simpler for inexperienced observers to decide whether a harmless or venomous snake has passed their way.

 

You can also view individual pages on each of Florida’s venomous snakes. These include additional characteristics, habitat notes, photos, range maps and other useful details.

 

Florida Museum of Natural History Website

The FMNH Snake Identification Key is based on the detailed identification tools used by professional herpetologists and serious snake-watchers. However, it has been modified to focus on color and pattern only – those characteristics that tend to catch the average observer’s attention, and which are easier to recall than finer details. Once you’ve eliminated characteristics that do not fit the snake you’ve seen, and have made a tentative identification, you can click on a photo and see if it matches your observation.

 

Using keys to identify a snake can be fun, and it’s easy to turn the process into a game that children will enjoy and benefit from.

 

Field Guides

I’ve relied on the Peterson Field Guides and their predecessors since childhood, and they remain the gold standard for on-site reptile and amphibian (and other animal) identifications. There is also a “first field guide” series and a wonderful field guide coloring book for children. Please check here for further information on these.

 

 

Further Reading

Venomous Snakebites: My experiences and a New Study

 

Black Mamba Memories 

 

Rattlesnake Overview

The dangers posed by a specific snake species depends upon a great many factors (please see below).  It is clear, however, that venomous snakes are a serious health concern…according to a recent study, each year’s 4.5 million venomous snakebites result in 100,000 deaths and 250,000 permanent disabilities (figures are approximate, please see the article linked below for details).  Certain large constrictors have also caused fatalities. In the course of field research in Venezuela, I observed a Green Anaconda attack a co-worker in what clearly was a feeding attempt.  Please see “Further Reading”, below, to read about both this incident and a recent study of human predation by Reticulated Pythons.   Today I’ll focus on the 2 most dangerous species that I’ve found most challenging as captives – the world’s largest and Africa’s longest venomous snakes, the King Cobra (Ophiophagus  hannah) and the Black Mamba (Dendroaspis polylepis).

 

A Note on “The Most Dangerous”

Widespread species that adapt well to human presence, such as Puff Adders, bite far more people than do, for example, sea snakes and others that might have more potent venom, but which rarely encounter humans.  Wild Black Mambas readily colonize farms and villages, benefitting from the increased availability of shelter and food (rodents, nesting birds).  King Cobras, on the other hand, tend to live in more undisturbed habitats.  Venom evolution, a snake’s size, the availability of antivenin, individual sensitivities and a host of other considerations also complicate the issue.

 

Here I’m mainly considering captive care (in zoos…venomous snakes should never be kept in private collections!).

 

Large, Alert, Fast and Smart!

Cobras and mambas are classified in the family Elapidae, which contains 354 members.  Among them we find several species that are considered to be high-strung and aggressive when confronted.  While King Cobras and Black Mambas often retreat if able, encounters in homes, barns or, in my case, zoo exhibits, may lead to attacks.  And the large size attained by each increases both the potential strike range and the amount of venom that may be delivered by a bite.

 

Another difficulty presented to zookeepers is the fact that cobras and mambas are hard to move via a snake hook.  Incredibly-fast and quick to figure out what’s going on, they more often than not land on the floor when being “hooked”.

 

For safety’s sake, I try to rely upon hunger and other “hands-off” tricks when relocating these formidable creatures (please see below), but that is not always possible.  While rummaging through a storage area in the Bronx Zoo’s reptile house, I once found a homemade shield used decades ago by keepers entering the King Cobra exhibit.  One keeper in particular was said to become very concerned if the cobras seemed hungry, or their cage needed servicing; armed with his shield, he would enter quite often (the King Cobras under my care moved into their shift cage when I needed to enter…or else they remained hungry!).

 

“Curious Cobras”

Those who work with King Cobras often describe them as “curious”.  I can’t disagree, although when servicing their exhibits I found this trait to be un-nerving, to say the least!   Actually, all cobra species I’ve cared for exhibited an unusual degree of alertness, and responded immediately to what was going on around them.  For example, both Egyptian and King Cobras, perhaps sensing my footsteps in the service area behind their exhibits, would rear up and face the small sliding window I looked through before opening their exhibit doors.  As I slid back the window’s cover, a cobra was nearly always peering back at me…in a lifetime of working with snakes, I’ve not seen this done by any other species.

 

My most harrowing King Cobra incident involved an escaped individual at an airport.  Fortunately, I went the “brains over brawn” route and emerged unscathed – much to the disappointment of the several young onlookers who expected a battle!  Please see this article for the details.

 

How Do You Get a Black Mamba into a Pillow Case?

This disturbing question confronted me when I was called upon to ship the Staten Island Zoo’s resident specimen to another institution.  If anything, mambas are faster and harder to deal with than cobras…individuals cornered in homes have quickly caused multiple fatalities.  An adult can deliver 120 mg of venom in a single bite, and the lethal dose is only 10-15 mg, so this is not a creature to be taken lightly.  Again, I shamelessly used under-handed tricks to accomplish my task…please see this article for the details.

 

King Cobra and Black Mamba Natural History

While much is made of the dangers posed by these snakes, less attention is paid to the details of their lives in the wild.  Mamba and cobra diets, breeding behaviors, threat displays and colonization of human-dominated landscapes are especially fascinating, and quite unique.  I’ve written about their natural behaviors in the articles linked below.

 

 

Further Reading

Anaconda Attacks: Notes from the Field

Human Predation by Wild Reticulated Pythons

Venomous Snakebites Worldwide

King Cobra Natural History

Black Mamba Natural History