#34 Observations of an Eastern Water Dragon

Having wildlife visit, or live in your garden provides a great opportunity to observe the habits of particular animals at length. A Water Dragon calls my fern garden home, and not only is he interesting to watch, he's also entertaining. My fern garden is on my back patio, so my resident dragon lizard can be easily seen basking, hunting and going about his daily life.

Are you talking about me?

When animals linger in my backyard for more than a fleeting visit, I give them a name - well I can hardly chat to my visitors without addressing them by name, can I? My Water Dragon is "Jacky", because upon first sight I presumed he was a Jacky Dragon (Amphibolurus muricatus), but comparing the two lizards, the differences are obvious.

This juvenile male Eastern Water Dragon (Physignathus lesueurii) arrived on my back porch in late February this year, disappeared for the three months of June, July and August for his winter rest (brumation), presumably in a sheltered spot in my fern garden, reappearing in late August.

Jacky crunches on a Green Carab Beetle (Calosoma schayeri). Presumably, lizards' taste buds are not well developed, because if this beetle tastes as bad as it smells, it should not make a very appetising meal.

Jacky has a routine: at first light he takes a dip in the pond in the fern garden, often sitting on a submerged rock with just his head out of the water. My pond is only small, so Jacky doesn't get the chance for a proper swim, but I have observed his swimming style: he tucks his limbs close to his body creating a streamlined form, and the side to side movement of the tail propels him through the water.

After his early morning swim, he perches on rocks at the front of the garden catching the morning sun, feeding on invertebrates at every opportunity.

In the afternoon when there is no sun on the garden, he often basks on a brick ledge in the sun, snatching hapless insects.

Teeth of an Eastern Water Dragon

Water Dragons (Physignathus lesueurii) do not lose and replace teeth throughout their life. They have a row of sharp pointed teeth adapted for grabbing and holding, fused to the jaw. The tongue is wide and thick. Both the tongue and interior of the mouth are pink.

I've seen my Water Dragon catch and eat cockroaches, slugs, worms, moths, ants, and a variety of small and tiny crawling and flying insects. He will only eat living invertebrates. He is extremely agile and swift.

Teeth of an Eastern Water Dragon

Scats (faeces) of a Water Dragon have a capping of white material at one end, which often becomes detatched. Droppings of my resident juvenile Water Dragon are about 10 to 12mm long.

Excrement of an Eastern Water Dragon

Learning to recognise scats of some locally common creatures, allows you to determine what animals visit your backyard. "Tracks, Scats and Other Traces - A Field Guide to Australian Mammals" by Barbara Triggs is a useful book.

Hearing of an Eastern Water Dragon

Reptiles do not have ear 'flaps' like mammals, but lizards have an external ear structure and therefore have adequate hearing.

The tympanic membrane, is a thin membrane that separates the external ear from the middle ear. The inner sinus in the middle ear cavity containing organs relating to balance and hearing, is filled with fluid in lizards and turtles, whilst in snakes, the recess is filled with air.

Airborn vibrations are picked up by the tympanic membrane. Snakes do not have a tympanic membrane, so can not 'hear', but detect substrate vibrations instead. The tympanic membrane of the Water Dragon is a small slightly-raised disc and can be seen in the close-up picture of the lizard head above. In some lizards, the Eastern Bearded Dragon (Pogona barbata), for example, the tympanic membrane is recessed.

An adult male Eastern Water Dragon

Hopefully, my resident Water Dragon will reach maturity and grow into a large impressive reptile as in the picture above. He will have to leave the security of my fern garden in order to grow to adulthood and breed.

But for the time being, Jacky must be eating well because he is currently moulting. Below is a series of images of the moulting process over two days.

The shedding of scales is called ecdysis, or, moulting or sloughing. Moulting serves a number of functions: my understanding is, firstly, the old and worn skin is replaced, secondly, it helps get rid of parasites such as mites and ticks. And as lizard scales do not grow with the body, moulting is necessary for growth.

The moulting started on the lower legs

The skin flaked off from bottom to top

At the end of day two, the skin peeled off the back

An Eastern Water Dragon (Physignathus lesueurii) is easily distinguished from similar dragon lizards by the presence of a thick black band running from the lower corner of the eye, extending over the tympanic membrane (ear), onto the neck.

A male can be recogised by the bright brick-red colouration of the belly. A male also has a more prominent spiny crest and more yellow patterning on the face and flanks.

I'm off for a swim

My resident Water Dragon is a regular source of interest and amusement as he scurries amongst the plants, leaping from vantage points to catch a feed. It is very satisfying to know that I am creating habitat for native creatures in my backyard that was a bare block of land a couple of years ago. I have recently planted many native shrubs and ground covers in an attempt to provide further habitat for small creatures and birds.

More Water Dragon observations and images can be viewed at my blog entry #12.