March 2022

What’s in a name

What is this snake we found in our garden? And what is it eating?

Answer

Common Tree Snake, snacking on a small Water Dragon. Photo: Lynda Bursford. Despite the differing colours, these are all the same species. Photos: Steve Wilson. The snake is a Common Tree Snake (Dendrelaphis punctulatus). It is a completely harmless, non-venomous species.

This is one of the most variably coloured snakes in Australia, which has led to an enormous amount of misunderstanding. Depending on colour or location, it goes under several names: Green Tree Snake, Blue Tree Snake, Yellow-bellied Black Snake and Golden Tree Snake. No wonder confusion reigns! Clearly most of these are not appropriate for the species as a whole, including the animal you have photographed. Because it is generally reasonably common where it occurs, we prefer the name Common Tree Snake.

In many areas, several colour forms occur together, but there are also some strong geographical trends. In eastern Australia, from about Sydney north-wards, green snakes with yellow bellies are quite typical. However, some individuals lack any yellow pigment, and as we learned at an early age when mixing paints at kindergarten, green minus yellow equals blue. Occasionally such individuals are quite a striking sky-blue.

Further north, for example around Townsville, the snakes are often black with a contrasting bright yellow belly. This is the Yellow-bellied Black Snake form. Across northern Australia, from Cape York to the Kimberleys, the snakes are almost invariably golden yellow.

The pale dashes on your snake are not normally visible. They are the pale scale-bases, usually concealed under the overlapping portions. When threatened the snakes can inflate a portion of the body, stretching the skin to suddenly reveal the contrasting paler colour. These hidden markings also become apparent when the snake is feeding.

Common Tree Snakes are extremely agile, thanks to their slender build and characteristic keels along the outer belly.  These give purchase while climbing, even enabling the ascent of a brick wall by following the angles of the mortar lines. The average rough barked tree trunk is a cinch, and they easily access outer branches and foliage.

Your snake is eating a Water Dragon. Like most Australian snakes, Common Tree Snakes feed exclusively on vertebrates. Frogs appear to comprise the bulk of their diet, but lizards are also favourites. Being completely non-venomous they can only eat prey that is easily overpowered. Captured animals are simply grasped, manipulated in the highly mobile jaws, and swallowed.

Want to know more? Our Discovery Centre is a free service open seven days per week, with experts ready to answer your questions. You can phone, write, contact us via our website or pop in. If we don’t know the answer we will try to find out for you.


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