Rear Fanged Snakes: Fascinating, Venomous, and Not a Good Pet Choice

South American Hognosed Snake

Uploaded to Wikipedia Commons by Matt872000

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.


Tentacled Snake

Uploaded to Wikipedia Commons by Rishaada

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.



Uploaded to Wikipedia Commons by Rishaada




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.


Twig Snake

Uploaded to Wikipedia Commons by Kwamikagami

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).



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


Mangrove snake

Uploaded to Wikipedia Commons by Seshadri.K.S

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!



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).


Green Vine Snake

Uploaded to Wikipedia Commons by Dimitri Eggenberger.

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?


Rosy Boa or Colombian Red-Tailed Boa? Choosing the Best Snake Pet

Large adult Boa Constrictor

Uploaded to Wikipedia Commons by Pavel Ševela

Boa Constrictors have been pet trade staples for decades. Of the 10 described subspecies, the Colombian or Red-Tailed Boa (Boa constrictor constrictor) is the best known, and is in fact one of the most popular snake pets. Commercially bred in huge numbers, the Colombian Boa is an excellent choice for some, but not all, snake enthusiasts.

North America’s Rosy Boa (Lichanura trivirgata), on the other hand, has only come into its own recently as a pet, but interest in now skyrocketing. Those with limited space who are seeking a “big snake in a small package” need look no further than this inoffensive beauty.

In the following article I’ll compare the care needs of Colombian and Rosy Boas, so that you’ll be able to plan ahead and maximize your pet-keeping experience and your snake’s quality of life. Detailed care information is provided in the articles linked under “Further Reading”. As always, please also post any questions you may have, and let me know which species gets your vote.


Rosy boa

Uploaded to Wikipedia Commons by Theodore Garland, Jr.


Although individual personalities vary, both adapt well to gentle handling. Rosy Boas tend to hide their heads when frightened, and their smooth, glossy scales may render handling a bit tricky. As with any snake, care and adult supervision must be exercised, and the animal’s head should never be allowed near one’s face.


Colombian Boas are not domesticated animals and must never be handled carelessly, as even long-term pets may react to scents or vibrations that people do not perceive. Bite wounds from Colombian Boas can be severe, and pets should never be carried about one’s neck (other similarly-sized constrictors have caused human fatalities by tightening quickly about a handler’s neck). Two experienced adults should always be on hand when specimens over 6 feet in length are fed, cleaned or handled.



Colombian Boas average 5-8 feet in length, and are stoutly built. However, some individuals grow quite a bit larger – up to 13 feet, 6 inches and 14 feet for the record holders, both captured in Surinam.


Averaging only 24-30 inches in length but also heavily-built for their size, Rosy Boas are obviously much easier than Colombian Boas to house and maintain.


Boa constrictor in natural habitat

Uploaded to Wikipedia Commons by Belizian

Activity Levels

Neither is overly active, but they regularly move between basking sites and shelters, and are likely to wander about the cage when hungry.


Life Span

The published longevity for a Colombian Boa is just over 40 years; pets regularly survive into their 20’s and 30’s.


The published longevity for a Rosy Boa is 29+ years (living at time of publication), and many captives approach and exceed age 20.


Newborn boa

Uploaded to Wikipedia Commons by DestructiveEyes

Breeding Potential

Both species breed reliably, and make an excellent introduction to this fascinating aspect of reptile-keeping. I especially like the fact that they bear live young, doing away with the time, expense and worry (for us!) of egg-incubation.



The purchase price for a normally-colored individual is similar for both snakes. Prices increase for rare or unusual color morphs – to $5,000 or more for “special” Colombian Boas!


However, the normal coloration of each species is spectacular, and natural variations, especially for the Rosy Boa, are seemingly endless. Several Rosy Boas that I encountered while studying insects in Baja California, which were blue-gray and marked with 3 pinkish-orange stripes, stand out as being among the most beautiful snakes I’ve seen.


The Colombian Boa’s great size makes it vastly-more expensive to keep when compared to its smaller cousin, the Rosy Boa.


Rosy boa, adult

Uploaded to Wikipedia Commons by Shane O. Pinnell

Terrarium Size (single adult)

Colombian Boa: 250-300 gallon terrarium or a huge custom-built cage


Rosy Boa: 20-30 gallon terrarium



Colombian Boa: 75-85 F, with a basking site of 90 -95 F; basking bulb and sub-tank pad recommended.


Rosy Boa: 75-85 F, with a basking site of 90-95 F



Food intake will vary among individuals and with temperature, season, life cycle stage, and other factors. Both accept pre-killed rodents.


Rosy Boa feeding

Uploaded to Wikipedia Commons by Cole Shatto

Colombian Boa: 1 appropriately-sized mouse each 7-10 days for youngsters. Adults do fine when offered an appropriately-sized rat each 10-14 days. Some keepers use guinea pigs or small rabbits for especially-large adults.


Rosy Boa: Fuzzies and young mice are preferable to adult mice (Rosy Boas have rather small heads and their jaws are ill-suited to swallowing large meals). Youngsters should be fed each 7-10 days, adults each 10-14 days.




Further Reading

Breeding the Rosy Boa

Boa Constrictors and Their Relatives: Care and Natural History




Eastern Painted Turtle Care: Keeping the USA’s Most Beautiful Turtle

PAINTED TUR, SMILEThose of us who are accustomed to seeing Eastern Painted Turtles (Chrysemys scripta scripta) in the wild and captivity sometimes take their beauty for granted. In my youth, I was able to find them quite easily near my Bronx home, and was surprised by the overseas demand when I began working for a local animal dealer. But upon close inspection, it’s easy to see why these aptly-named turtles are wildly-popular in zoos and private collections worldwide. In addition to their brilliant coloration, Eastern Painted Turtles make hardy, long-lived and responsive pets (if given proper care!). They have all the qualities that have made Red-Eared Sliders so popular, but their smaller size and calm demeanor renders them a far better choice for most turtle enthusiasts.


320px-Eastern_Painted_Turtle_(Chrysemys_picta_picta)Natural History

The Eastern Painted Turtle’s range extends from southern Canada along the eastern seaboard of the USA to Georgia, and west to central Alabama. Three subspecies – the Southern, Midland and Western Painted Turtles – range across southern Canada and through most of the USA to northern Mexico. All hybridize where their ranges overlap, and in captivity.


Type habitat

Uploaded to Wikipedia Commons by FWS

Painted Turtles favor slow-moving, well-vegetated waters, and are most commonly encountered in swamps, marshes, river oxbows, creeks, and small ponds on farms and even golf courses (I caught my first specimen, as a child, by hopping a golf course fence and sloshing through its tiny pond – that incident remains my only golf-related experience!). I once was surprised to find a hatchling in a tidal river on Long Island, but have since learned that they are known to enter brackish water.


Turtle Behavior in Captivity

Like many semi-aquatic turtles, Eastern Painteds quickly learn to associate their owners with food, and will paddle over to beg when you approach. Ever-alert, wild individuals plunge from basking sites when startled, but pets are generally quite fearless. Most feed readily from the hand, and they may even reproduce.


Young painted turtle

Uploaded to Wikipedia Commons by US Bureau of Land Management


Female Eastern Painted Turtles reach 7-9 inches in length, while males generally top out at 5 inches. An adult female will require a 30 to (preferably) 40 or 55 gallon aquarium; a male might make due in a 20 gallon “long-style”, but more room is preferable.


Zoo Med’s Turtle Tub is an excellent option for larger individuals. Plastic storage bins, if properly outfitted, may also be used.


Wading pools are often easier to manage than aquariums. Koi ponds sometimes contain shelves meant to hold plants; these work well as turtle basking areas. Outdoor housing is ideal, assuming that raccoons and other predators can be excluded.



Uploaded to Wikipedia Commons by Tony Gamble

Although highly aquatic, Painted Turtles need a dry surface on which to bask. Commercial turtle docks will suffice for smaller specimens. Cork bark, wedged or affixed via silicone to the aquarium’s sides, is a good option for adults.



Turtles are messy feeders and very hard on water quality. Submersible or canister filters are necessary unless the enclosure can be emptied and cleaned several times weekly (I’ve found the Zoo Med Turtle Clean Filter to be ideal). Even with filtration, partial water changes are essential.


Southern Painted Turtle

Uploaded to Wikipedia Commons by Suzanne L Collins (CNAH)

Removing your turtles to an easily-cleaned container for feeding will lessen the filter’s workload and help to keep the water clear.



Bare-bottomed aquariums are best, as gravel traps food and wastes, greatly complicating cleaning. If gravel is used, it should be of a size too large to be swallowed.



Heliothermic turtles (those that bask) require UVB exposure in captivity. Natural sunlight is the best UVB source, but be aware that glass filters-out UVB rays.


If a florescent bulb is used (the Zoo Med 10.0 Bulb is an excellent product), be sure that the turtle can bask within 6-12 inches of it. Mercury vapor bulbs broadcast UVB over greater distances, and also provide beneficial UVA radiation.


Western Painted Turtle plastron

Uploaded to Wikipedia Commons by Matt Young


Water temperatures of 75-80 F should be maintained. An incandescent bulb should be used to warm the basking site to 88-90 F.



Painted turtles will eat or harass fishes, newts and aquatic frogs.


Individuals of the same sex may get along, but aggression often develops so be prepared to house them separately. It’s difficult to keep pairs together long-term, as the males’ continual mating attempts usually lead to stress and bite wounds.



Painted Turtles begin life as carnivores but increasingly consume aquatic plants as they mature. Pets favor animal-based foods, but should be encouraged to eat plants; a fasting period will tempt them to sample new items.


Dandelion, kale, mustard and collared greens, romaine and other produce should be offered. Aquatic plants such as Elodea, Anachris and Duckweed may also be accepted. Spinach and beet leaves are high in oxalic acid and have been implicated in health problems.


mediaZoo Med Aquatic Turtle Food and Reptomin Food Sticks provide excellent nutrition and can serve as 50-75% of the diet. Other commercial aquatic turtle diets and treats are also worth investigating.


Natural foods should always be included in turtle diets. Whole freshwater fishes such as minnows and shiners are the best source of calcium for turtles. Offer fish at least once weekly, but use goldfishes sparingly as a steady goldfish diet has been implicated in liver ailments in other species.


Other important food items include earthworms, krill, freeze-dried river shrimp and crickets, waxworms and other insects.



Wild females become sexually mature at age 5-10, males at age 3-5. Courting and breeding occurs in May and June, and females deposit 1-4 clutches of eggs (1-15 eggs in total) between May and July. Late-hatching young may overwinter in the nest and emerge the following spring.


Captive conditions may alter all of the above, so please write in for detailed information on how best to breed your pets in their particular environment.


Health Considerations

Salmonella bacteria, commonly present in turtle digestive tracts, can cause severe illnesses in people. Handling an animal will not cause an infection, as the bacteria must be ingested. Salmonella infections are easy to avoid via the use of proper hygiene. Wash your hands with warm, soapy water after handling any animal. Please speak with your family doctor concerning details, and feel free to write me for links to useful resources.




Further Reading

Providing Nesting Sites to Female Turtles

Commercial Turtle Diets: Pellets, Shrimp and Prepared Foods

Monitor Lizards as Pets: Dumeril Monitor Care and Natural History

The Dumeril’s or Brown Rough-Necked Monitor (Varanus dumerilii) is still collected from the wild, but captive breeding is increasing, and will, I hope, soon be the rule rather than the exception. Although the black and orange hatchlings are hard to resist, Dumeril ownership should not be entered into lightly. Strong and active, adults may top 4.5 feet in length, and are best reserved for those with adequate space and experience. That being said, Dumeril’s Monitors are reputed to be somewhat easier to handle than other similarly sized species. My own experience bears this out, but individual personalities vary greatly…caution and respect for their powerful jaws and sharp claws is a must. For those up to it, this is definitely a species worth considering, as it is little studied in the wild and unprotected across much of its range (and a very interesting creature as well!).


Dumeril's Monitor

Uploaded to Wikipedia Commons by Katerina Zareva, EERC Sofia Zoo


The Dumeril’s Monitor sports a “typical” monitor build and averages 3-4 feet in length, with some individuals approaching 5 feet. Hatchlings and very young individuals are brilliantly clad in black and orange. Adults are attractively-marked in various shades of brown and tan. Extremely sharp claws (even by monitor standards!) assist it in climbing.



The Dumeril’s Monitor is found across a huge range that extends from southern Myanmar and Thailand through western Malaysia and much of Indonesia to Singapore. The population on Singapore was long believed extinct, with no reported sightings since 1935. However, a single individual was collected in the island’s Nee Soon Swamp Forest in 2008, spurring hopes that it is still hanging on there.


Typical habitat

Uploaded to Wikipedia Commons by Tho nau


The Dumeril’s Monitor inhabits lowland forests, coastal mangrove swamps and swamp forests. Village and farm outskirts are sometimes colonized, but the effects of habitat development on this species have not been studied. It is at times highly arboreal, but also frequently forages on the ground and in the shallows of rivers and swamps.



Like most of their relatives, Dumeril’s Monitors are quite active, and will not thrive in close quarters. Adults require custom-built cages measuring at least 6 x 4 x 6 feet.


Cypress mulch or eucalyptus bark may be used as a substrate. Shy by nature, they are best provided with numerous caves, cork bark rolls and hollow logs in which to shelter, and stout climbing branches for climbing. Some individuals prefer sheltering above ground (wild individuals reportedly utilize tree hollows), so a cork bark roll or large nest box positioned among the branches would be ideal. A water bowl large enough for soaking should always be available…the ideal Dumeril’s enclosure would feature a large, drainable pool.


The cage should be located in a quiet, undisturbed area of the home, as Dumeril’s Monitors are very aware of their surroundings, and easily stressed.



Dumeril’s Monitors fare best when afforded a temperature gradient of 78-85 F; nighttime temperatures should not dip below 75 F. The basking site should be kept at 110-120 F. Incandescent bulbs may be used by day; ceramic heaters or red/black reptile “night bulbs” are useful after dark.


Provide your monitor with the largest home possible, so that a thermal gradient (areas of different temperatures) can be established. Thermal gradients, critical to good health, allow reptiles to regulate their body temperature by moving between hot and cooler areas. In small or poorly ventilated enclosures, the entire area soon takes on the basking site temperature.



Humidity should average 70-85%, but dry areas must be available. A commercial reptile mister will be helpful if your home is especially dry.



While there is some evidence that UVB exposure may not be essential if the animal is fed properly, I always provide it to monitors in zoo exhibits and at home. In most situations, UVB exposure is the safest option. If a florescent bulb is used (Zoo Med bulbs are ideal), be sure that your pet can bask within 6-12 inches of it. Mercury vapor bulbs broadcast UVB over greater distances, and provide beneficial UVA radiation as well.


Fiddler crabs

Uploaded to Wikipedia Commons by Melongal


The few available studies indicate that wild Dumeril’s Monitors take a wide variety of prey animals, including grasshoppers, roaches, and other large insects, frogs, crabs, snails, bats, rodents and other small mammals, birds and their eggs, turtle eggs, and fish. Populations living in mangrove swamps seem to favor crabs and snails…in my experience, crabs and crayfish always elicit a vigorous feeding response from captives.


Hornworm (sphynx moth larvae)

Uploaded to Wikipedia Commons by Shhewitt

I do not use a rodent-only diet for these or other monitors from similar habitats (i.e. the Black Rough-Necked Monitor). Youngsters should be fed largely upon roaches, super mealworms, earthworms, snails, hornworms and other invertebrates, along with small whole fishes, un-shelled shrimp, fiddler and green crabs, crayfish and squid. Pinkies or small mice may be provided once weekly, and hard-boiled eggs can be used on occasion. All meals (other than fishes, crabs and rodents) offered to growing monitors should be powdered with calcium, and a high-quality reptile vitamin/mineral supplement should be used 3x weekly. I favor ReptiVite and ReptiCalcium.


Rodents and whole fish can comprise 50% of the adult diet, with a variety of large insects, earthworms, hard-boiled eggs, crayfish, crabs, shrimp, snails, and similar foods making up the balance. Calcium and vitamin/mineral supplements should be used 1-2x weekly. Large food items should be avoided; even where adult monitors are concerned, mice are preferable to small rats.



Although not a species for beginners, Dumeril’s Monitors adjust well to captivity when given proper care, and make fine, long-lived pets. Initially shy, some learn to trust gentle caretakers, while others – especially wild-caught individuals – remain wary. A large, well-furnished cage will provide the security that is essential if they are to become approachable.


In common with all monitors, they are capable of inflicting serious injuries with their powerful jaws, long tails and sharp claws. Thick leather gloves should be worn when handling Dumeril’s Monitors, as even tame individuals leave deep scratches with their claws in the course of their normal movements.



A single male can be housed with 1 or 2 females, but they must be watched carefully. The nesting area should be enclosed (i.e. a large tub or plastic storage container within a wooden box equipped with an entrance hole) and stocked with 2-3 feet of a slightly moist mix of sand, top soil and peat moss.


We have a good deal to learn about captive reproduction. Success (and failure) has been reported under a wide variety of conditions. Please post below for detailed information on pairing adults and incubating the eggs.




Further Reading


Monitor Ownership: Important Considerations

Monitor Learning Abilities


Terrarium Plants: Best Hardy Houseplants for Reptile and Amphibian Tanks

House plants in terrariums

Uploaded to Wikipedia Commons by Baumpython

When I first began keeping reptiles and amphibians a lifetime ago, the live plants at my disposal were limited to cuttings I could beg, borrow or steal from my green-thumbed mother. Today we are very fortunate in having an astonishing variety of available orchids, mosses, ferns and plants ideally suited for use with reptiles and amphibians. For those of us with wide interests, this diversity is a real pleasure…in fact, co-workers at the Bronx Zoo have at times accused me of expending more effort on my exhibits’ flora than its fauna! But in both zoo exhibits and at home, I frequently fall back on old favorites, especially several inexpensive and readily available house plants. If you are not skilled or interested in plant propagation, but wish to provide your pets with the many benefits that live plants confer, the following species should be of interest. The plants covered here are but a small sample…please post notes about your own favorites below.


Note: Please post below if you intend to keep live plants with herbivorous lizards or turtles, so that we can discuss any problems may arise if foliage is consumed. Please see the article linked below for information concerning pesticides that may be present on commercially-grown plants.


Wild Pothos

Uploaded to Wikipedia Commons by Nyanatusita

Pothos or Devil’s Ivy (Epipremnum aureum)

This attractive, hardy vine is one of my favorite plants for use in terrarium and zoo exhibits. Widespread from India to northern Australia (and feral elsewhere), Pothos will grow equally-well in sphagnum moss, water, soil or gravel. If rooted in shallow water, it takes the form of an emergent plant, and thus looks well in bog terrariums. Grown as a floating plant, it will send out long roots, creating a dramatic effect and helping to improve water quality. Draped over logs and rocks, or left hanging, sinuous aerial roots will quickly form, lending an “over-grown” effect to your terrarium.


Many folks are surprised to learn that Pothos left unchecked can become quite large – I measured the leaves of some old specimens in Bronx Zoo bird exhibits at nearly 3 feet in length and 14 inches in width  (please see photo).


Peace Lily

Uploaded to Wikipedia Commons by Kurt Stüber

Peace Lilly (Spathiphyllum spp.)

This very familiar house and office plant is another that can be used on land or in water. Much like Pothos, its root system is quite dramatic when seen below water, and will be used as a hiding and foraging site by newts, aquatic frogs, small turtles and similar creatures. I’ve written a separate article on its care and use…please see the link below.






Other Useful, Hardy Houseplants

Earth Star

Uploaded to Wikipedia Commons by Chhe

Earth Star (Cryptanthus spp.): I learned about this Bromeliad from an arachnologist who kept spiders in unlit terrariums. It is nearly indestructible, and excellent for use with spiders, amphibians and other animals that prefer low light levels; the leaves flush red when exposed to light.


Jade Plant (Crassula ovata): A beautiful succulent, ideal for desert and semi-desert terrariums; the thick branches take on fantastic shapes.


Lucky Bamboo (Dracaena sanderiana): native to West Africa and not related to true bamboo, this popular plant is usually sold rooted in water. Kept so, it makes a nice emergent “swamp” type plant, or it can be planted moist soil.


Heartleaf Philodendron (Philodendron scandens oxycardium)

Arrowhead Vine (Syngonium podophyllum)

Chinese Evergreen (Aglaonema modestum)

Miniature Wax Plant (Hoya bella)

Dwarf Columnae

Uploaded to Wikipedia Commons by Franz Xaver

Dwarf Columnea (Columnea microphylla)

Spider Plant (Chlorophytum comosum variegatum)

Zebra Plant (Aphalandra squarrosa)

Asparagus Fern (Asparagus densiflorus)

Bird’s Nest Fern (Asplenium nidus)

Miniature Creeping Fig (Ficus pumila minima)

Hooked Strap Plant (Anthurium hookeri).

Coffee Plant (Coffa arabica)


Further Reading

The Peace Lily as a Terrarium Plant

Terrarium-Safe Plants: Avoiding Pesticides

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