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

Like most reptile keepers, I have often marveled at the efficiency of snake digestive systems.  I attributed their abilities to break down bone to “powerful digestive enzymes”, but recent research has shown that, at least for Burmese Pythons (Python molurus), a far more complex and amazing process is at work.

Digesting Large Vertebrates

I’ve observed some quite large snake feasts – a Red Foot Tortoise and a 60 pound deer taken by Green Anacondas (the tortoise was an unfortunate exhibit mate; the deer fell to an anaconda at my study site in Venezuela) and 40 pound pigs regularly fed to Reticulated and Burmese Pythons under my care at the Bronx Zoo, for example.

A few shell scutes, hoofs, some bone fragments and fur where all that passed in the feces of these snakes – the rest being digested.  How do they do it?

Bone-Digesting Cells

Research at the Louis Pasteur and Indiana Universities has revealed that, after feeding, the digestive systems of Burmese Pythons undergo a dramatic transformation.  New cells are produced and worn-out cells die and are eliminated in preparation for the work at hand.

Studies of the small intestine have uncovered a new type of cell, previously unknown to science.  These cells are responsible for degrading bone and releasing its components into the snake’s bloodstream.  This process promotes efficient calcium absorption, and may be the reason that most captive snakes do not require a UVB source if fed a diet comprised of whole rats, mice and other vertebrates.

Warm-Blooded Snakes?  Not Quite, but…

We’ve known for some time now that Burmese Pythons break the “cold-blooded” rule when digesting their meals.  While most snakes must seek out a hot basking spot in order to maximize digestion, Burmese Pythons can actually raise their internal temperatures without an external heat source! 

Further Reading

Please see Big Snake Meals for some examples of how large (and unusual) snake prey can be.

To read about recent research concerning another unusual snake feeding adaptation, please see How Snakes Grow despite Food Deprivation.

An account of the original research showing that pythons can raise their body temperatures may be found in this Journal of Herpetology article.

Coating feeder insects with calcium and vitamin supplements is a time-tested method of adding important nutrients to reptile and amphibian diets.  However, shy and nocturnal species that do not eat soon after the insects are released into their terrariums may get little benefit from powdered supplements.  Insects quickly lose their coatings as they move about…crickets and roaches add to the problem by grooming the supplements from their bodies as soon as they are able (Yes, “grooming” …watch roaches sometime, they are quite fastidious!).

Spray-On Calcium

R Zilla Reptile Calcium Supplement Spray and Vitamin Supplement Spray help to address this problem.  The spray sticks to and may even be absorbed by insects (as well as dry foods and salad), thereby assuring its delivery no matter how much time elapses before the food is consumed.  These products will prove particularly useful to those keeping Leaf Tailed Geckos, Crocodile Skinks, Flying Geckos, Red-Eyed Treefrogs, Spadefoot Toads, certain burrowing tarantulas and others that are notoriously shy about showing themselves by day.

Calcium Spray supplies calcium in three forms, including Calcium Gluconate, which is readily utilized by many species.  It can also be administered orally to animals with deficiencies (a consultation with your veterinarian would be advisable beforehand).

Further Reading

Please see my article Providing a Balanced Diet to Reptiles and Amphibians for more information on other aspects of captive herp nutrition.

An interesting article on feeder insect calcium content is posted here.

 Next time we’ll take a look at a few effective but little-used techniques for raising the calcium content of insects fed to reptiles and amphibians. 

Agalychnis callidryas image referenced from wikipedia and originally posted by Christian R. Linder

With over 1,200 species, the skink family (Scincidae) is the lizard world’s largest, and in it we find some very unusual creatures.  Yet one, the Crocodile Skink (Tribolonotus gracilis), stands out as being particularly unique even in this odd assemblage of reptiles.  Originally thought to be a difficult animal to keep, we are now learning more and more about it, and captive reproduction is no longer a rarity.  Let’s take a look at how this skink distinguishes itself.

Description

This species departs radically from the typical skink body plan.  The head is enlarged, triangular in shape and capped with helmet-like scales, while four rows of thick, pointed scales line the back.  Its color is dark brown to black, with a striking red or orange area about the eye.  Crocodile Skinks average 6.5-7.8 inches in length.

Range

The Crocodile Skink is found only in Papua New Guinea and on the nearby Admiralty Islands.  One additional species, the Spiny Skink, T. novaeguinea, (which also appears in the pet trade) inhabits New Guinea, and 6 other species within the genus are found on the Solomon Islands and in New Caledonia.

Habitat

Crocodile Skinks frequent damp, shaded mountain valleys near streams and, in contrast to most skinks (and lizards in general!), they prefer temperatures of 66-75 F.

Again unlike most skinks, they are largely nocturnal or crepuscular (active in early mornings and evenings).  Although declining in some areas, recent observations indicate that piles of coconut husks on farms provide important habitat, and may help populations to increase.

Reproduction

Here again the rules are broken, with females laying only 1 egg at a time.  Oddly, the left ovary and oviduct are somewhat regressed in development as compared to the right.  The single egg developing on the left side is not laid until approximately 60 days after the right ovary’s egg has been laid.   This is true for 7 of the 8 species of Tribolonotus…Schmidt’s Helmet Skink (T. schmidti) gives birth to a single live offspring.   Well-fed female Crocodile Skinks may produce up to 6 eggs each year.

Female Crocodile Skinks guard their eggs during the 70 day incubation period.  In captivity they cover the eggs with substrate when foraging and lunge at intruders.  The hatchlings stay in close proximity to the female for approximately 2 weeks.  Further study may reveal an even greater degree of social behavior, as males kept in the same enclosure are not hostile to the young or to the female.

Other Unusual Characteristics

Crocodile Skinks are unique among lizards in having glands under the abdominal scales, on the surface of the hands, and on the undersides of the feet.  The function of these glands is not completely understood.

They also vocalize when disturbed – producing quite a loud “squawk” for such a small creature – and feign death when stressed.  I can attest that both behaviors are very surprising to the uninitiated!  Some vocalizations may be in response to egg disturbance – another lizard “first” (please see article below).

Further Reading

An interesting article detailing work carried out at the Dallas Zoo on Crocodile Skink vocalizations is posted here.

To read more about the largest lizard family, please see my article Skinks: an Overview.

A video of rarely seen display behavior is posted here.

I’ll cover the care of these most unusual lizards in a future article. 

The Desert Tortoise (Gopherus agassizi), was, in the 1960’s, a pet trade staple.  A lack of information as to its proper care and massive habitat loss has today reduced populations to alarmingly low levels.  The species is now protected, and a great deal of research has gone into its husbandry and natural history.  Yet, it seems, few appreciate just how unique this animal is.  Today I’d like to highlight some of its lesser known habits, and how they affect the future of the species.

Tortoise Diversity

Desert Tortoises are one of four tortoise species, all of the same genus, native to North America.  All are terrestrial vegetarians with forelegs modified for burrowing.

An additional 49 species of tortoises inhabit Africa (where they reach their greatest diversity), Europe, South America and Asia.  Tortoises are absent from Australia and Antarctica.

Winter Migrations

Desert Tortoises are found from southeastern California’s Mojave Desert, southwestern Arizona, southern Nevada and southwestern Utah south to northern Baja California and northern Sinaloa, Mexico, and on Tiburon Island in Gulf of California.

It is in the northern part of this range where we find a most unique winter survival strategy. Here, desert tortoises migrate to hilly areas at the onset of cold weather and hibernate in communal burrows that are 15-33 feet in length. It seems that a burrow of suitable length (over 15 feet) could not be dug by a single tortoise in one season, so these long-established burrows (and traditional migration routes) are critical to winter survival.

Effective conservation planning requires an understanding of such factors – permanent hibernation burrows may be far from the tortoises’ summer foraging areas, and thus not recognized as essential habitat when preserves are set aside.  Populations deprived of migration routes to hibernation sites will become extinct in a single winter.

Summer nights are spent in shallow, self dug burrows that are often utilized for many years.

Good Intentions Gone Bad

Another unusual impediment to Desert Tortoise conservation arose when, with good intentions, large numbers of seemingly healthy pet tortoises were returned to the wild.  These animals were responsible for introducing a virulent but difficult-to-detect respiratory illness into wild populations.  Control measures are now in place in the USA.

Desert Tortoises inhabit the centerpiece exhibit of the new reptile house at the Staten Island Zoo, which I was proud to help plan several years ago.  Please see the attached photo above, and visit if you are able.

Further Reading

A wealth of information on Desert Tortoise Conservation is posted here.

A wonderful video of a Desert Tortoise egg hatching is posted here.

Please see Parts I and II of this article for additional information on garter snake husbandry and natural history.  Today I’ll cover some often over-looked aspects of garter snake care that may help to explain why these relatively hardy snakes, and the related ribbon and water snakes, often fail to live as long as might be expected in captivity.

Thermal Gradient

A thermal gradient (varying temperatures within the terrarium) is beneficial to nearly all reptiles, but seems particularly important in maintaining the health of captive garter snakes.  This is especially true for Butler’s Garter Snakes (T. butleri), Common Garter Snakes (T. sirtalis) and others that range into the northern half of the USA.

Depending upon the species in question, garter, ribbon and water snakes do best at an ambient temperature of 72-82 F, with a warmer basking site (90-95 F) and a drop to 68 F or so at night.  Northern species should ideally be subjected to a winter cooling-off period, even if breeding is not contemplated.

UVA Light

There is some evidence that garter and related snakes (as well as Rough and Smooth Green Snakes, Opheodrys aestivus and O. vernalis), may benefit from exposure to UVA light.

A ZooMed Repti Halogen Bulb should be provided during their normal daytime cycle.  Even if not strictly necessary for survival, UVA encourages natural behavior, reproduction and, possibly, a strong immune system.

UVB Light

While snakes have not been shown to require UVB light exposure, anecdotal reports from successful garter and water snake keepers lead me to believe that these snakes may differ from most in this regard.

The Zoo Med 2.0 fluorescent lamp is specifically designed for animals needing moderate amounts of UVB light, and may be a prudent addition to the garter snake terrarium.  This bulb also supports vigorous plant growth…in contrast to most snake species, garter and ribbon snakes are very well-suited for terrariums housing sturdy live plants.

Further Reading

Laboratory guidelines concerning the importance of thermal gradients and related aspects of reptile care are posted here.

Next time we’ll cover nutrition and the care of individual garter snake species.