Goanna in the Roof!

Sometimes there are animals sharing the spaces we occupy most frequently and they are so cryptic, we may never see them.

This great photo was taken by mum fabulous mum who is becoming quite the wildlife photographer! I'd tried a few stints sitting patiently and waiting for this elusive lizard to emerge while visiting my parents' place, but with no luck. Yesterday mum went outside, saw the lizard, rushed in and managed to not only return with her (small point-and-shoot) camera but sneak incredibly close for this shot. So... what IS IT!!??

Well, this is a Black-headed Monitor, (Varanus tristis), a common but rarely seen arboreal (tree-dwelling) monitor. It is one of the most widespread of our goannas, occurring over most of Australia and varying quite a bit in colour across its range. The animals here in the Perth Hills appear almost entirely black, but if you look closely you can see the fine pattern of paler circles (called 'ocelli') over the back.

'Tristis' is a brilliant climber and spends much of its time ascending trees (what a life!), hiding in hollows and crevices in bark. It can also sqeeeeeeze into small spaces: I have watched one climbing upwards inside a hollow branch turn completely back on itself and start heading down, in a narrow space only 4cm wide! Since European settlement, tristis has also taken to living in rooves, hence this photo. The lizards are probably attracted here because of the complex structural environment of beams, cracks, nooks and crannies in which they can hide, which offer a safe refuge from predators. Gutters also provide a nice sunny place in which to bask!

Furthermore, many rooves contain rats and mice, a valuable food source, and the monitors probably find it quite easy to smell their way into a rat's nest and devour the babies. They also feed on frogs, birds' eggs and a variety of insects, including many which are garden pests. For this reason and the fact they help keep our rat and mice numbers down, they are a huge asset to your garden!

A problem arises when we want to get rid of rats and mice in our roof, and use poison to do so. Poisons are always something we should treat with caution but so often people don't waste any time in using them without thinking of the consequences. Animals like the Black-headed Monitor, and other vertebrates including owls, hawks, bandicoots and your very own dog or cat, will be killed via secondary poisoning if they find a dead or dying rat and take a bite. Strychnine, the most common chemical in rat poisons, kills the animal by causing muscular convulsions and eventually asphyxia, so its not the nicest way to die! But there is one poison, called Racumin by Bayer, which kills rats and mice without causing secondary poisoning. If you must use a poison, make sure you seek out some of this stuff (it's available in local hardware shops, just ask around), and do your bit to keep our local wildlife safe.