The water dragon is a diurnal, semi-aquatic, arboreal, tropical lizard of Asia and Australia. The Asian water dragon (Physignathus cocincinus) is mainly green in color, with darker areas on the head and joints. The chin and throat are white to light yellow, and the underside is white to pale green.
The eastern water dragon (Physignathus lesueurii), from Australia, resembles the Asian water dragon in size and shape but is brown in color, with a gray to gray-brown underside. Broad black and narrow white crossbars run through the back and the tail of the animal. A prominent dark horizontal stripe may be visible on each side of the head, starting from the eye towards the neck. Like the Asian species, a dorsal crest runs from the head to the tail.
Water dragons do not have a dewlap, but instead possess large skin folds. A prominent dorsal crest runs from the neck to the tail. Juveniles are typically diagonally banded with 3 to 5 light stripes, usually pale blue to green in color, which disappear with age.
Water dragons live in humid, sub-tropical to tropical forests, tropical rain forest, wooded streams and rocky shores. Most adults usually reach 50 cm in length, (the tail counting for half to two-thirds of the length), but some can reach up to a meter in length. Longevity up to 11 years has been recorded.
Water dragons are less aggressive and more placid than green iguanas, although are prone to intense spurts of speed. They are also smaller and therefore more manageable, but like most diurnal lizards they require a large spacious enclosure with high quality lighting and heating. All lizards can excrete Salmonella and therefore routine personal hygiene and the supervision of all child-water dragon interactions are important.
Water dragons are active but usually timid. They may attempt to flee when disturbed, often hitting their water bowl or the glass of the enclosure. Water dragons can sometimes be intolerant to other animals, so it is recommended to keep either a pair (male and female) or up to a male and two females together as a maximum in a single vivarium.
Water dragons need a large enclosure. They will literally rub their flesh off trying to get out of a too small enclosure. They need space at least 2 times their total length – which is a minimum of 6 feet long (side to side), at least 2 to 3 feet deep and 4 to 6 feet high. Large enclosures permit landscaping, a bigger water pool and an overall improvement in the aesthetics of the set-up. The enclosure should be high enough to allow plenty of branches so the lizard can bask under a heat lamp or spotlight during the day.
These lizards are semi-aquatic and should be provided with a large water area in their enclosure, covering preferably at least a third of the floor area. The water should be maintained at 77 degrees Fahrenheit (25 degrees Celsius). In most cases the general heating of the enclosure is sufficient, but an aquarium heater or a heat mat placed underneath the water container can be employed if necessary. This water body will also provide high humidity to the enclosure, which is essential for these lizards.
For hygienic reasons the floor is most easily lined with newspaper, although granulated bark, artificial turf and alfalfa pellets can be used. Replace the floor covering daily or weekly depending on contamination. Other than the branches for basking areas, provide boxes, pieces of bark or hollow tree for retreat areas.
Asian and Australian can be kept together, with one to three males in a room-sized enclosure. Some females can be domineering and may not want any other females around; others can co-habit with 3 or 4 females. You must monitor your pets to assure all are feeding and basking properly. If any aren’t, it is probably because of intimidation and you will need to increase the number of basking and feeding areas, increase enclosure size or separate them.
Water dragons will try to escape from an unsuitable environment or evade dominant cage-mates. They do not seem to perceive glass, screen, or other clear material as a barrier and might damage their nose by attempting to escape through these surfaces. You can try creating a visual barrier by putting tape across the glass to help them perceive these obstacles.
Water dragons are mainly carnivorous, feeding on a wide variety of invertebrates, small mammals, birds, lizards, frogs and also on rare occasion on fruits and plant matter. In captivity they should be fed insects (crickets, locusts, waxworms), the occasional pink mice, and will rarely accept fruits or vegetables.
All insects should be nutrient gut loaded by feeding a commercial insect food or a mix of crushed fish pellets and calcium supplement, with a slice of potato for moisture. In addition, all insects should be thoroughly dusted with a high calcium supplement immediately prior to feeding. It is wise to vary the food items to avoid potential nutrient excesses or deficiencies and multivitamins can be added to the dusting formula once or twice weekly.
Juveniles should be fed the same diet as the adults, like insects (crickets, locusts and waxworms), making sure smaller food items are used. As they grow they may accept some fruits, as well as pink mice. Juveniles should be fed every day while adults can be fed every other day or 2 to 3 times a week.
Heat should be provided by a background heater (tubular heater, infrared through heaters, heat mats, etc) and a radiant daytime heater (infrared ceramic bulbs, incandescent spotlights). These should be screened in order to prevent any contact burns with the water dragon.
The diurnal temperature variation is vital for proper digestion and assimilation of food, and general health. A daytime temperature gradient of 77 to 86 F (25 to 30 C), with a basking area of 90 to 95 F (32 to 35 C), should be lowered to 72 to 77 F (22 to 25 C) at night. Use a digital in/out thermometer with max/min memory to record the day and night thermal gradients within the vivarium.
Humidity of 80 to 100 percent is required for at least part of the day. If the large water area does not create enough humidity in the enclosure, regular spraying can help. Never reduce ventilation to increase humidity.
The recommended photoperiod is for water dragons is 12 to 14 hours of light and 10 to 12 hours of darkness. Ideally, you should provide access to unfiltered sunlight, but if this is not possible, provide a full spectrum light source that must be placed within 30 cm (12 inches) of the basking sites and replaced every 6 months for juveniles or 12 months for adults.
Males are larger than the females, and their dorsal crest is more developed. Although both sexes possess pre-femoral pores, there are much more developed in the mature male. A hemipenal bulge can also be seen at the base of the tail in mature males.
Sexual maturity is usually reached at one year of age, with the animals measuring around 40 cm in length. Breeding usually occurs during the winter and early spring. Males in breeding condition will become brightly colored from golden-yellow to deep orange on the chin, chest and side of the head.
The female water dragon can lay up to five clutches of eggs in one season, with each clutch containing 10 to 15 eggs. An egg-laying container should be placed in a remote area of the enclosure for egg laying. The eggs are best incubated on damp vermiculite at 82 to 86 F (28 to 30 C), and the babies should hatch between 60 days to 101 days.
Neonates measure around 15 cm in length at birth. Their care is similar to the adults; they should be raised in groups and fed on insects dusted with mineral supplements and given access to unfiltered sunlight or broad-spectrum, artificial lighting.