Uncommon Facts about a Common Pet Lizard: The Prehensile-tailed Skink, a/k/a Monkey-tailed or Solomon Island Skink (Corucia zebrata)

Monkey Tailed SkinkThe 1,200+ skink species form the largest lizard family, Scincidae, and among them we find quite a number of unusual animals. Yet the prehensile-tailed skink manages to distinguish itself as unique in not one, but many ways.Largely unknown in the pet trade until the late 1980’s, these arboreal skinks became widely available when logging in the Solomon Islands brought their formerly inaccessible treetop homes crashing to the ground, and left the lizards in reach of collectors. I and others noticed right away that they were quite different than anything we had run across previously.

A Highly Social Lizard
The limited field studies suggest, and our captive observations support, that prehensile-tailed skinks live in hierarchal colonies (a reptilian social group is known as a circulus) and exhibit a variety of highly-developed social behaviors. Group members seem to recognize one another by scent, and mark their territories with waxy secretions. Although often found in pairs, up to 10 individuals have been collected from a single tree hollow, but the functioning of these groups is not understood.

A Placenta and a Giant Offspring
Females, which average 24 inches in length, have a true placenta. They produce 1, rarely 2, huge (to 13 inches) offspring after an amazingly long gestation period of 6 – 8 months. Esteemed veterinarian and herpetologist Dr. Kevin Wright has likened this feat to that of a woman giving birth to a 6 year old child!

Complex Parental Care
The young stay close to their mothers for some time and the females become very aggressive towards people and other skinks after giving birth. Although we do not as yet understand the interactions between adults and young, it is quite clear that those reared in isolation exhibit, if you will, “anti-social” behavior (they are noticeably more aggressive than other skinks, to the point of charging people opening the door of their cages).

Coprophagy (eating of feces) is common, and some believe that this provides the young with important intestinal flora. Breeding occurs year round in the wild and captivity. The young begin feeding at about 10 days of age, and reach sexual maturity in 10 months to 1 year.

Much More to Learn
All told, a strange and fascinating beast. Although captive longevities approach 25 years, we have yet to scratch the surface when it come to understanding prehensile-tailed skink social interactions. This is definitely an animal to focus on; I’ll cover captive care in the future…until then, please write in with your observations and questions.

The American Association of Zookeepers has posted an informative article on this species’ fascinating social structure at:

My Animal Collection: How a Herpetologist Keeps Barking Treefrogs (Hyla gratiosa) and Gray Treefrogs (Hyla versicolor)

Hi, Frank Indiviglio here. Today I would like to offer a look at how I set up a terrarium for animals in my own collection. After decades keeping animals privately and professionally, my techniques have become a fusion of tried and true methods and ideas that I have either worked out or (often!) stumbled across. Of primary importance has been the writings and personal advice of many kind and dedicated people.

Wonderful but Neglected Terrarium Pets
Frogs in My Battery Jar Terrarium I’ve never quite understood why barking and gray treefrogs have remained largely ignored by herptoculturists. Both are beautifully patterned – the gray frog subtly, the barker often quite brilliantly – and almost always make themselves right at home in captivity. Wild caught adults of either species have hand-fed for me as soon as 1 week after capture, and a gray treefrog that I have now approaches the glass when I enter the room, in a much more “turtle” than “frog-like fashion”. At nearly 3 inches in length (and appearing larger due to its stocky frame), the barker is the USA’s largest native treefrog, exceeded only slightly in size by the introduced Cuban treefrog (Osteopilus septentrionalis).

Setting Up a Battery Jar Terrarium
I currently keep 1 barking and 1 gray treefrog in a battery jar terrarium of about 10 gallon capacity. I favor battery jars for the simple reason that they were always mentioned in the naturalist/pet-keeping books of yesteryear. As a child, I had no idea what a battery jar was, but imagined it to be a fabulously exotic item, the possession of which would confer instant “professional animal-keeper” status upon me.

In reality, battery jars are thick-walled, usually cylindrical glass containers available from biological/laboratory supply houses. Their vertical orientation serves arboreal frogs well, but a 20 gallon “extra-hi” aquarium or larger plastic terrarium is also perfectly suitable.

My battery jar was modified for use as a terrarium by Bob Holland, a friend who was well-known in the 60’s and 70’s for his success in keeping – years ahead of most public collections – poison frogs, banded tree snails, woodland salamanders, mosses, ferns and a host of other delicate organisms.

Bob used aquarium silicone and a piece of glass to create a small pool and to attach a hollow piece of lava rock about ½ way up one side of the terrarium. The lava rock functions as a planter, and the area below as secure shelter…the treefrogs rarely use it, but in earlier times it was favored by a marbled salamander (Ambystoma opacum).

My skillful friend cut a ventilation panel into the terrarium’s glass top, a task I would not attempt. Commercial glass cutters can do this for you if you are as “tool-challenged” as I, after which you can silicone a piece of fine screening in place.

The substrate is Eco earth loose coconut with a bit of sphagnum moss mixed in. A layer of aquarium gravel and activated carbon, situated below the substrate, assists in drainage and ammonia absorption. I use live, locally collected moss on top of the substrate – you’ll need to experiment with the moss species, but many do well with moderate lighting and daily misting. Compressed frog moss works well to fill in dark corners, or as a substrate for the entire tank if you prefer.

Live Plants, Light and Decorations
I chose the live plants for this terrarium based upon their serviceability as frog perches and modest light requirements. The aptly-named cast iron plant (Aspidistra elatior) is nearly indestructible, and is often used as a perching site. The Chinese evergreen (Aglaonema modesta), snake plant (Sansiveria spp., not pictured) and earth star (Cryptanthus spp.) are equally hardy. Earth stars are a favorite of tarantula-keepers, as they get by on very little light (they turn brown at such times, but return to red when moved to a brighter location).

A Reptisun 2.0 florescent bulb provides sufficient light for the plants without exposing the frogs to harmful levels of UVB – most amphibians have UVB “filters” in their skin, and actively avoid the sun.

A Caution Concerning Light
Another Frog Terrarium ShotI have noticed corneal opacities in green and gray treefrogs that consistently perch directly below even low-level UVB output bulbs. To be on the safe side, keep track of your frogs’ perching habits. Most tend to choose the same spot day after day, and it is usually an easy matter to fashion a shield (i.e. an artificial plant) between the frog and the bulb.

A few attractively-weathered pieces of driftwood provide additional climbing surfaces. Exo terra terrarium plants are extremely life-like, more so when integrated among living plants. I find them especially useful in creating exhibits in zoos and museums, where the plant species used must match those found in the subject animal’s habitat, or where light levels limit the use of live plants.

One drawback of a battery jar terrarium is the relatively small area that can be vented. In the summer, temperatures within may become too warm for most amphibians, if even a florescent light is used. The aforementioned plants will usually survive on room light alone for a few months – to be safe, I set the terrarium light to go on for 2-3 hours during the cool of morning.

Plants as Waste Managers
I always fear downplaying the importance of regular cleaning, and it is not my intention to do that here. However, well-planted terrariums that are lightly stocked with animals are a delight to maintain.

The key is to have enough plants with vigorous root systems, live moss if possible and to find the right balance of plants and animals. The tank pictured here would actually be more easily maintained with just 2 gray treefrogs, or a single barking treefrog, as opposed to 1 of each, but I am familiar with its capabilities, and monitor it carefully. This terrarium has been up and running, with only two major substrate changes (one after housing a sick animal), for nearly 12 years.

Help From Snails and Sowbugs
In addition to the plants, I am assisted in tank maintenance by a thriving colony of land snails and sowbugs (Check Out: Terrestrial Isopods as Food for Captive Reptiles and Amphibians ). Both avidly consume the frogs’ waste products and decaying plant material, and neither requires additional food. The sowbugs provide an alternative food source for the frogs as well. I spot clean when necessary, occasionally replace the top inch of substrate, and change the pool’s water by wicking it out with paper towels. A layer of activated carbon below the substrate (an old trick now largely forgotten) helps to absorb nitrogenous wastes.

Feeding Native Treefrogs
Wild Caught Insects
Frog swallowing a hand-fed cricketMy gray treefrog hatched in captivity, and the barker acts as though it did – both feed avidly from the hand. This allows me to more easily provide a varied diet, as they will take canned insects such as caterpillars and grasshoppers. From spring through fall, I feed the frogs exclusively upon insects that I trap with a Zoo Med Bug Napper or collect around my outdoor yard light. An insect or 2 each day or so suffices, and the dietary variety is key to good health (Check Out: Providing a Balanced Diet to Reptiles and Amphibians).

This is just a thought, but I believe it cannot hurt to attempt to provide arboreal and flying insects to tree frogs – especially so if you live within the range of the frogs that you keep. Mine favor moths, tree crickets, small katydids, caterpillars, beetles, harvestman (“daddy longlegs”) and flies. I avoid spiders, fireflies, ladybugs and brightly colored species, due to possible toxicity problems, and do not collect for a week or so after the area has been sprayed to control West Nile virus ( I believe the plane-sprayed insecticides kill far more cicadas than mosquitoes, but I digress…).

Commercially Available Insects
During the winter, temperatures in the terrarium average 62-65 F, the light cycle is reduced to 8 hours, and the frogs slow down. A once-weekly feeding of crickets (use only small ones for gray treefrogs), mealworm beetles, waxworms and earthworms holds them until tastier meals return (most treefrogs refuse earthworms, but some individuals will accept them).

I powder feeder insects with a vitamin/mineral supplement during the winter only – I’ve found such is unnecessary in summer, when wild caught insects dominate the diet.

The frogs and terrarium are sprayed once or twice daily with de-chlorinated water (both species use the pool as well).

I’m sure that many of you have developed your own twists to herp-keeping. Please write in and I‘ll share your thoughts in future articles. Thanks, until next time, Frank.

There are 2 nearly identical species of gray treefrog in the Eastern USA. You can learn how to distinguish them, and a bit about the National Wildlife Federation’s laudable Frogwatch USA Program, at:


Research Update – Researchers Identify the Bacterium That Causes Fatal Diseases in Pet Trade and Rare Desert Lizards

A newly discovered bacteria species (Deviriesea agamarum) is responsible for a variety of fatal organ diseases that currently plague captive lizard populations, according to an article in the September, 2008 issue of The International Journal of Systematic and Evolutionary Microbiology. Particularly hard-hit has been a breeding program for the highly endangered Oman dab lizard, Uromastyx thomasi, but a number of other desert-dwelling lizards in the genera Uromastyx and Agama are susceptible as well. The bacterium is related to others that cause human skin infections.The identification of the bacterium has important implications not only for the treatment of disease in captive lizards, but also for wild populations. Captive-bred reptiles that are used in reintroduction programs may appear healthy but harbor diseases that can decimate wild populations. Some years ago, this very situation caused serious respiratory disease outbreaks among desert tortoise populations in the American southwest, and led to a ban on the release of confiscated tortoises. Similarly, the September 23, 2008 issue of Current Biology states that many amphibian species in Europe are currently threatened by a fatal Chytrid fungus that was introduced to the wild by Mallorcan midwife toads released as part of a reintroduction effort.

Please write in with your comments and questions. Thanks, until next time, Frank Indiviglio.

You can read more about disease problems that affect reintroduction programs at:

Incubating Reptile Eggs – A Simple Method of Monitoring Moisture Content

The moisture content of the substrate upon which reptile eggs are incubated is a critical factor in hatching success. While certain hardy species fare well under the much-promoted technique of “squeezing water from the substrate until it barely sticks together”, many eggs require closer attention to detail.

Equipment Needed
I would like to pass along a method that I have used for hundreds of species, both in zoos and in my own collection. All that is required by way of measuring devices is a simple gram scale and a graduated cylinder (marked off in milliliters). Fortunately for me and other mathematically impaired herpers, calculations are simple – it turns out that 1 milliliter of water weighs 1 gram.

The Technique
First, determine the moisture level required by the eggs that you are incubating (please write in if you need help with this). Then, using the gram scale, weigh out enough substrate contain the eggs. You can now easily set up a ratio of, for example, 1 part substrate to 1 part water, by measuring, in the graduated cylinder, a corresponding volume of water. So, 10 milliliters of water added to 10 grams of vermiculite provides a 1:1 ratio (1:1 works well for many, but not all, reptiles).

Place the eggs (1/2 buried for most reptiles) and moistened substrate into a sealed container, weigh the container and record the weight (and date) on the cover. The cover should not be ventilated – for most reptile eggs, a once- daily check provides enough oxygen exchange (ventilation may need to be increased for large numbers of eggs once hatching time nears – please write in if unsure).

Keeping Track of Moisture Loss
Weigh the container weekly – any weight loss will be the result of evaporation, and should be made up by adding an appropriate volume of water to the substrate. For example, if the container weighs ½ gram less than the previous week, add ½ ml. of water.

Please look for future articles on egg incubation. Until then, please write in with your questions and comments. Thanks, Frank

The abstract of an interesting article on the conservation of moisture in reptile eggs is posted at:

Terrestrial Isopods (Sowbugs, Pillbugs, Potato Bugs) As Food for Captive Reptiles and Amphibians

Isopods, more commonly known as sowbugs, pillbugs or potato bugs, are a valuable but largely neglected food source for pet amphibians and reptiles. The over 10,000 described species are common in most habitats worldwide, and are therefore an important in the diets many creatures. Ranging in size from .02 to 20 inches, there is an isopod to fit every feeding need (public aquariums pay $600 or more each for giant, deep-sea forms, so don’t plan on feeding these to your monitor lizards!).

Nutritious, Interesting Scavengers
Isopods are crustaceans, and as such provide a variety of nutrients not to be found in insects. Another thing I like about using them has to do with their appetites – they will eat anything, so by feeding them a rich and varied diet you are improving their value as food items for your pets. Furthermore, native sowbugs and pillbugs will live in most terrariums and are valuable scavengers, relishing dead earthworms, crickets and feces. I always include a group in naturalistic habitats that I design for zoos and museums. Finally, they are very interesting to observe in their own right. They do contain quite a bit of chitin, so are not suitable as the sole item in a diet.

Obtaining Isopods
Temperate isopods prefer cool, moist environments, and so are most easily found in spring and fall. You can collect them below rocks and leaf litter. They will also flock to cover such as boards placed on the ground, especially if the area is kept moist and baited with coffee grounds or ripe fruit. Biological supply houses also sell starter cultures.

Keeping and Breeding Isopods
Keep your colony in a vented plastic container with 3-4 inches of R-Zilla Coconut Husk as a substrate. Plastic terrariums by Lee, Tom Aquarium, Hagen and PLA House make ideal isopod homes. Be sure to keep the bedding moist but not wet. A covering of Zoo Med Terrarium Moss will help retain moisture and offer shelter to the isopods, making collection easier.

A mix of R-Zilla Alfalfa Meal Bedding and Tetra Min Flake Fish Food is an excellent basic diet, to which can be added grass clippings, leaf litter, coffee grounds and almost any fruit or vegetable. A cool basement makes an ideal location for the colony, but average room temperatures are fine. Be sure to keep an eye on moisture levels during hot, dry periods. A breeding colony will supply huge numbers of isopods of all sizes.

My Experience
I have always kept an isopod colony for my collection, and have used them in zoos as well. They are easy to maintain, breed readily and are, I think, one of the best-kept secrets (no more!) in herptoculture. Very few insectivorous herps refuse them, and they are readily taken by many fishes and birds as well. Be sure to try a group in your naturalistic terrariums also, as they make fine scavengers and, unlike crickets, they will not attack debilitated pets.

I’ll cover other alternative food items in the future. This area is of particular interest to me…I would be most pleased to receive your observations, comments and questions. Thanks, Frank Indiviglio.

The University of Arizona’s Center for Insect Science Education offers a wealth of information on native invertebrates in the wild and captivity. Read more about isopods at:

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