Goannas (or Monitor Lizards) radiated from the north to Africa and Australia during the Miocene epoch, around 15 million years ago and have an important place in our history and culture.  They were an important traditional native food source and are commonly represented in Aboriginal Dreamtime stories.

Today there are 27 surviving species of these large lizards in Australia, most are carnivorous. All have a similar body shape to their original ancestors and have sharp teeth and claws to help them hunt and eat.  Size is the distinguishing feature of Australian monitors; the largest is the Perentie (V. giganteus), which grows over 2m long, and the smallest: the Short-tailed Monitor (V. brevicuda), grows to just 20cm.  Monitors are commonly dark-coloured or white and orange-yellow in the desert.  Most have camouflage bands, speckles or spots relating to their environments, though these differ between species and age groups. They can live up to 40 years in the wild.

Goannas mostly live on the ground and dig holes for nests or burrows to protect eggs from predators and provide a constant temperature for embryo development. The Heath Monitor (also known as Rosenberg’s Monitor) and Lace Monitor  will dig holes into the side of termite mounds to lay their eggs.  This is clever as the termites then rebuild the nest around the eggs, keeping them safe and at a constant temperature. Unlike Heath Monitors, mother Lace Monitors will return when the young hatch, to help dig them out.  Several species, including the Perentie, hibernate during the coldest months (from about May to August).  Ridge-tailed Monitors get their name from the raised and pointed scales on their tails, which they wedge into rock crevices, making it harder for predators to pull them out.

Goannas are surprisingly good climbers. In fact, Lace Monitors are known as Tree Goannas and are thought to eat more bird eggs than other goanna species.  While they may appear slow, goannas are fast runners and will sprint short distances on their hind legs – often to the safety of water or a tree. The Sand Monitor is sometimes called Gould’s Monitor or the Racehorse Goanna for its speed. Goannas are also known to rear up on their hind legs to scare off attackers or fight, but they’ll also do it to look around for threats from a higher vantage point.

Water Monitors are excellent swimmers and can stay underwater for several minutes hunting for food such as fish, frogs, crabs or shrimps.  Monitors eat just about anything they can catch and swallow whole. Prey is dependent on the size of the goanna but includes insects, birds, eggs, small reptiles and mammals.

In northern Australia crocodile eggs are a favourite food. They’ll also scavenge for carrion and are attracted to rotting meat.

As predators and scavengers goannas play an important role in each of the ecosystems they inhabit. They maintain population numbers of prey species and keep disease loads low through the removal of carcasses. Monitors have adapted to a range of environments and vary in their hunting methods, such as digging, swimming and tree-climbing.

They use their long forked tongues as snakes do, flickering to detect prey through scent molecules in the air.

If you do any travelling in outback Australia you’ve got a good chance of seeing goannas. They’re most active in the day, and like to spend time basking in the sun. They’re mostly solitary, except for mating sea13P/Olbersson in spring and summer.

It was only in 2005 that goannas were discovered to have venom glands similar to snakes. However, they don’t have enough venom to cause serious harm and lack fangs to inject into prey. Nonetheless, goannas have a great deal of bacteria in their mouths and a bite will often turn into a nasty infection, so caution and a healthy dose of respect are called for if you see a monitor in the bush!

Threats to Australian monitors include habitat loss due to land clearing for agriculture and urban space. Monitors prey on Cane Toads and suffer from the poison glands exuded by the toads, so the spread of Cane Toads has caused declines in many areas, most recently the Kimberley.

Habitat degradation and removal of termite mounds and other habitat features such as fallen timber have a significant impact on some goanna species. Invasive mammals and generalist predators such as foxes and cats may also prey on young monitors.

The two species found in the Bendigo region:

Sand Goanna – Also known as the Gould’s Goanna and Sand Monitor it is a large lizard with a laterally compressed tail. Local specimens range from light yellow to almost black, usually with numerous small scattered, lighter and darker flecks and spots to form cross bans. A common feature is a pale-edged dark stripe running from behind the eye to the neck. All limbs have pale spots. The tail is usually banded close to the body but the distal quarter to two-thirds is often pale.

It is diurnal and terrestrial with arboreal habits. Runs very fast and will rapidly ascend trees when disturbed. It is an active predator and scavenger that forages for any prey that it can catch and over power. It tracks down and digs out lizards and their eggs, turtle eggs, insects spiders, scorpions, centipedes and small mammals. Mating occurs in Spring and 3 to 11 eggs ae laid into a long deep nest burrow. This is plugged and concealed by the female. Hatchlings are seen in mid to late summer.

Lace Monitor – A large formidable lizard with a long, slender, laterally compressed tail and large claws. Widely variable IN COLOUR AND PATTERN. Typically, bluish grey to black with numerous scattered white, cream or yellow scalers or groups of scales forming larger spots and blotches. The tail and snout usually banded. Juveniles tend to be more brightly coloured. The throat is often brightly coloured, sometimes even appearing blue. Diurnal and predominantly arboreal, sheltering in large old hollow trees.

This lizard can run very fast and rapidly ascend trees when disturbed. It is known to forage up to 3 kilometres per day. It is a voracious and opportunistic predator, taking a variety of prey including birds, mammals, reptiles, insects, vertebrate eggs and carrion. Gorging is not uncommon. Solitary in habit, however it will tolerate aggregations of its own kind at abundant food sources, such as large carcass or when scavenging at picnic grounds. Breeding is in late Spring and Summer and male combat is common during this time. Females lay up to 20 eggs usually in a termite mound on the ground, or in a rotting log or other decomposing organic matter. When hatching is due the female returns and breaks open the termite mound to facilitate the hatchlings escape. After this there is no more parental care.