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Contains articles and advice on a wide variety of snake species. Answers and addresses questions on species husbandry, captive status, breeding, news and conservation issues concerning lizards.

Mate Selection and Sperm Competition in the Painted Dragon, Ctenophorus pictus, and Other Reptiles

Females of many animal species are polyandrous, meaning that they mate with several males. Often, we are learning, the sperm survives for some time inside the female, and competes with the sperm of other males. In this way, only the “fittest” sperm will prevail and fertilize the eggs, assuring vigorous offspring. Females choose mates based on a wide variety of factors, and the criterion used by Australia’s painted dragon lizards turn out to be quite unique.

In contrast to most lizards, male painted dragons have either red or yellow heads, and are chosen by females based on their head color. Research published this week (WollongoGreen Anacondang University) has revealed that female dragons do not choose 1 color over another, but rather seek to mate with 1 male having a red head and 1 with a yellow head.It is theorized that by choosing males of both colors, the female is assuring that she is mating with more than 1 male, and not with the same male twice.

Polyandry among reptiles can result in amazing spectacles – I shall never forget the sight of a huge “breeding ball” – 9 males and 1 female- of green anacondas, Eunectes murinus, on the Venezuelan llanos. In many different animals, sperm can remain alive and able to fertilize eggs for years to come. Queen termites mate once and somehow produce fertilized eggs for up to 20 years after!

Further information concerning research with this species at Wollongong University is available at:


Learning in Rhinoceros Iguanas, Monitors and Other Lizards – observations on zoo animals

Rhinoceros Iguana

Observant lizard keepers cannot fail to become aware of the surprising degree of intelligence exhibited by many species. In the course of my long career at the Bronx Zoo, I was fortunate to have been able to observe the learning abilities of a number of species not often available in the pet trade.

Although species and individuals varied markedly in their capacities, one constant seemed to be that all recognized and responded to changes in their normal routine. This makes sense, of course, from the viewpoint of survival, but I was none-the-less always impressed by the rapidity at which most learned.

Rhinoceros iguanas, Cyclura cornuta, and water monitors, Varanus salvator, were particularly striking in this regard. Animals in the collection for over 15 years, long in the habit of approaching or ignoring a single keeper in their exhibit for routine maintenance, would flee if 2 people entered. It took but 1-2 incidents for them to learn that 2 people meant trouble – i.e. a veterinary exam, but that 1 person meant no harm. The animals unfailingly retained this knowledge over a period of years, even without reinforcement by new events.


An interesting article on intelligence in monitor lizards is posted at:

Bearded Dragon Care and History in Captivity

Bearded Dragon Picture

The inland bearded dragon (aka bearded dragon), Pogona vitticeps, is an extremely popular pet, both here and abroad. However, wide availability does not signify that this lizard should in any way be “taken for granted” – it is a fascinating animal, and recent research has uncovered startling facts about it. As is true for even the hardiest of lizards, the bearded dragon also has very specific needs, which must be met if it is to thrive as a pet.

Younger hobbyists may be surprised to learn that this species was virtually unknown in the USA, even in zoos, not long ago. As a youngster, I knew it only from the occasional photograph, and longed to view one in the flesh. Today, the inland bearded dragon is a pet trade staple, with thousands being bred by hobbyists each year. Oddly enough, all pet trade animals seem to have originated from a small group smuggled out of Australia (where they are strictly protected) to Germany in the early 1980’s. They are legal to own in the USA, but, technically…..

In 2005, researchers at Australia’s Melbourne University discovered, much to the surprise of the herpetological community, that the bearded dragon has glands that produce mild venom. Apparently harmless to people, the venom seems to be holdover from the distant past. Bearded dragons are the only members of their family, the Agamidae, thus far known to produce venom. Several unrelated lizards, such as the beaded lizards, Helodema horridum, Gila monsters, H. suspectum, Komodo dragons, Varanus komodoensis and lace monitors V. varius, also produce venoms of varying strengths.

The inland bearded dragon is found in central Australia and in non-coastal areas of eastern Australia. Six additional species range throughout the continent and into New Guinea. It favors dry savannah and scrub, semi-deserts, rocky outcrops and open forest. Although a ground-dweller, the bearded dragon climbs well and uses rocks and stumps as basking sites and as platforms from which to launch attacks on insects moving about below. Diurnal, it basks at temperatures of 125 F for short periods and shelters in self-dug burrows during extremely hot or cold weather.

To read the rest of this article, click here: Bearded Dragon Care and History in Captivity

Sheltopusik or Eurasian Glass Lizard History and Care

Eurasian Glass Lizard

Although often passed by in favor of more brightly colored lizards, the sheltopusik, or Eurasian glass lizard, Ophisaurus (Pseudopus) apodus, makes an interesting, hardy and responsive pet. One formerly under my care at NYC’s Staten Island Zoo is approaching 30 years of age, and still in vigorous good health. The captive record is 54 years (the longest, I believe, of any lizard), and longevities of 20-30 years are not uncommon.

Furthermore, the sheltopusik is uncommonly responsive (especially to those who provide its meals!) and accepts a wide variety of foods – pink (new-born) mice, crickets, earthworms, mealworms, waxworms, eggs, canned lizard diet and canned dog and cat food – to name a few. Cone-shaped teeth assist in crushing snails, a favored prey. After eating snails, sheltopusiks remove the snails’ slime from their jaws by rubbing their mouths against the ground. In the wild, they actively forage for beetles, spiders, grasshoppers, caterpillars, mice, shrews, voles, ground nesting birds and their eggs, small snakes, lizards and their eggs, and carrion. Averaging 2-3 feet in length, exceptionally large specimens can top 4 feet.

Glass lizards, as their name implies, quickly autotomize (shed) their tails when handled or captured by a predator. The eastern glass lizard, O. ventralis, of the southeastern USA and Europe’s slow-worm, Anguis fragilis (note the species’ name!) are particularly adapt in this regard. Pet sheltopusiks usually become so tame that tail shedding is rarely a consideration if they are handled gently.


Interesting sheltopusik photos are posted at:

An Introduction to Geckos

Some of our most familiar and desirable of reptile pets, such as the leopard gecko and the brilliantly-colored day geckos, are members of a fascinating family of lizards that I would like to introduce today.

The 1,050 or more species of geckos comprise the second largest of lizard families, the Gekkonidae (the largest is the Scincidae, or skinks). They range throughout the world, reaching their greatest diversity in desert and tropical habitats. “House geckos” of several species follow human habitation and are widely transplanted, including into the southeastern USA. Geckos range in size from the various Shaerodactylus species, some of which are full grown at 1.2 inches in length, to the New Caledonian giant gecko, Rhacodactylus leachianus, a bulky creature that tops out at nearly 15 inches. Several other species, now considered extinct but which may possibly still survive in Madagascar’s forest canopy, reached 24 inches in length.
Adult Leopard Gecko
Geckos generally lay 2 eggs, although some bear live young. Arboreal types often glue their eggs to tree branches or building walls. Most are insectivorous, but many take nectar and over-ripe fruits as well. The voracious tokay gecko, Gekko gecko, consumes nestling birds, small rodents and bats, snakes and other lizards. A number of species are highly endangered while others, such as the leopard gecko, Eublepharis macularius, are pet trade staples. Many have a long association with people, being welcome in homes for their insect-catching abilities and sometimes regarded as good luck symbols. Some years back, a store in NYC even rented tokay geckos for use as roach-control agents. However, the males’ habit of calling loudly (“Tokay-Tokay!”) at 4 AM and their pugnacious dispositions rendered the scheme less-than-profitable!

The ability of many geckos to climb sheer walls (even glass) and to run upside-down on ceilings was first recorded by Aristotle in the 4th century BC. Only recently has the secret behind this remarkable phenomenon been discovered. The toes of many species are covered with layered pads known as lamellae, which in turn support thousands of microscopic hair-like structures called setae. Their action against a surface sets up a weak molecular attraction known as the van-der-Waals force, and this, it seems, is the source of their unique method of adhesion. This phenomenon Tokay Geckois being studied with a view towards creating new adhesives for use in industry.

Members of this huge family have evolved startling adaptations to a number of basic themes. To cite just one example – depending upon the species, tails are used to distract predators (by disengaging from the body), plug burrows, extrude noxious secretions, create sound, communicate with others, convey stability while gliding, store food and grip branches.


If you have a special interest in geckos, you may wish to join the Global Gecko Association, or to visit their website for further information:


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