Australian Lizards

Australian lizards

Text and images by Simon Watharow and Steve Cook

 

 

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Australia has an amazingly diverse, unique and exciting range of lizards. It is a privilege to research and learn more about them. We have explored many parts of the country to study them and present a few simple facts about them here.

 

 

Lizards can be found in all states and all habitat types, even in the alpine regions. While it is true to say that there are more species the further north you go, as lizards prefer the higher temperatures and consistently warmer weather conditions, they are also frequent in the south.

 

In the southern states lizards will enter a state of inactivity after a series of cold nights in late summer or autumn, and will remain dormant during winter until the warmer weather triggers an emergence in the spring or the beginning of the wet season. The warmer months are when you are most likely to see lizards in the southern states.

 

Lizards will often be seen moving about habitats and in yards and crossing roads. They will occupy a variety of microhabitats from leaf liter, in trees hollows or exposed bark, exfoliating rocks and matted vegetation to subterranean, such as under lose sand or ant/termite mounds. In semi-arid and arid regions hummock grass is a haven for lizards, especially geckos, skinks and the legless. Australian habitats support perhaps the largest lizard density and species diversity in the world.

 

            There are no true venomous lizards in Australia, but we do know that there are advanced saliva enzymes and proteins that are very primitive forms of venom, and some lizards actually have basic venom glands. The two true venomous lizards are the Gila monster and beaded lizards found in the United States and Mexico. They have harmful venom properties. In time with research more will come to light about Australian lizard venom.

 

 

 

Lizard activity

 

While all lizards require elevated temperatures to become active, forage for food, reproduce and metabolise food, they have various strategies in how they get their heat. Some species bask in direct light, known as heliothermic behaviour. Others use the warm surfaces of rock, trees or leaf litter but do not emerge into true sunlight.

 

It may surprise you but heat stress is critical in reptiles. Caught out on hot days and exposed to 35–40 degree temperatures for longer than 40–60 minutes may be fatal. So lizards will shuttle between bushes in shade then back out in the sun, then retreat into shade then back out to prevent overheating. Some lizards will also have heat-avoidance strategies, such as colour change in dragons, to reduce heat.

 

As lizards do not respire or have water loss through sweat, which cools down mammals like people when they get hot, a few will simply open their mouths while others will use burrows or shade to help drop their internal body temperature. During the hottest part of a summer day it’s not unusual for most lizards to be sheltering to avoid the potential for heat stress. Once the days have ebbed and started to cool down they will remerge if they need to. Monitor lizards, due to their behaviour of long-distance foraging, simply cool off in the shade while others, such as Lace monitors and the water monitors, take a swim in a river or lake.

 

 

 

 

 

Wildlife secret

 

It is now accepted that some species of lizards have very mild forms of modified saliva glands that are primitive venom. They are not of the neuro-toxic kind prevalent in venomous snakes, but they can disrupt blood factors and cause mild pain.

 

 

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Agamidae: dragon lizards

 

Dragons may be seen more often in arid and semi-arid areas of Australia. There are several species, though, that are widespread across the country. They range from the ta-ta lizards to the various bearded dragons and the iconic Frilled Lizard. They are frequently seen basking on rocks, logs, woodpiles, ground crests or ridges, in shrubs or branches.

 

Dragons like the Mallee and Painted are short-living; just 8–12 months. The larger species are believed to live for 5–12 years in the wild and up to 20 years in captivity. All dragons feed on invertebrates, with some expanding their diet to include vegetation, especially flowers. Dragons like the bizarre and colourful Thorny Devil or Mallee Dragon feed primarily on ants, but most dragons are opportunistic.

 

            Larger dragons have threat displays, opening mouths and erecting bearded or frills to inflate their appearance and intimidate. While they can bite it is rarely cause for concern, except the surprise and shock. The best and most often relied upon defence they have, though, is camouflage. Their rough skin, often edged with soft spines or skies [check this work ???? Scales??], makes them look fierce. Surprisingly, dragons can be shy and retiring.

 

Some have elaborate courtship and male combat rituals, such as head bobbing and arm waving. The common ta-ta lizard, which is made up of several Lophognathus species, often waves its front leg in a slow rhythmic wave.

 

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Gekkonidae: geckos

 

Australian geckos are usually small, about 40–300 mm in size. They are often well known for their ability to climb smooth surfaces, such as glass or walls. They can achieve this because of adhesive hairs on their feet. Not all geckos have these hairs; quite a few are bound to ground level and have only clawed feet. Geckos also have a fleshy tongue that helps clean their eyes by wiping out sand or dirt.

 

Australia has two introduced species, including the widespread Asian house gecko, which is very aggressive and tends to exclude  native species like Gehyra australis.

 

Geckos are nocturnal, remaining in burrows under bark or logs or hidden in spinifex until dusk, when they start to emerge and forage for invertebrates. Some rely on speed if they forage in the open or others move slowly around trees, using camouflage to keep them safe from predators. All geckos lay one to two eggs in a burrow or under logs or inside spinifex.

 

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Pygopodidae: flap-footed or legless lizards

 

This family is quite amazing. They range in size from 60–800 mm. Typically most sightings of legless lizards are usually mistaken for snakes. The small clearly legless appearance tends to have them killed as potential dangers to the household. But legless lizards have an ear opening, remnant legs (flaps) and fleshy, not forked, tongue.

 

While they do not have the free-flowing aspect of movement that snakes do, these lizards move more erratically. Some legless lizards have even gone a step further and use mimicry to look just like a baby snake; for example, the Delma species have black heads just like baby brown snakes. Often when uncovered some species rear up and flick a fleshy tongue out rapidly, just like a surprised snake. It is difficult to identify a legless lizard from a snake so it is best to treat all such animals as venomous!

 

The most well-known legless lizard is the widespread Burton’s Legless Lizard. It is a large thick 300–450 mm long lizard that is found across the country, except in Tasmania and southern Victoria. Common scaly-foots can be seen in eastern Australia, while Hooded scaly-foots lived in semi-arid to arid Australia. Various species of Delma occur and some have the dark or patterned head.

 

            All legless lizards are invertebrate predators, although one is a lizard specialist and few may show a strong preference for spiders or scorpions or termites. They move slowly through shrubs, leaf liter or spinifex searching for prey. While largely nocturnal some, like the scaly-foots, will be active in spring at daylight hours.

 

            Like geckos and skinks legless lizards can practice tail autonomy when threatened or grabbed by a predator.

 

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Scincidae: skinks

 

This is the largest group of lizards in the world. There are skinks in just about every habitat. They are abundant in nearly all yards and range from the garden skink to the well-known blue-tongued lizard.

 

Skinks often have smooth scales, and range from the terrestrial foraging shinglebacks to tree-climbing Tree skinks and sand-swimming skinks, which survive in upper levels of sand and emerge only to grab prey. The most well known are the garden skinks, which are actually myriad species that live across the country and have adapted to life in the urban garden. They forage inside the layers of leaf litter for the many invertebrates that survive there.

 

Along waterways various species of water skinks can be seen basking and watching for tadpoles, aquatic invertebrates and larval forms. Around small shrubs and spinifex, medium-sized skinks can be seen darting from one bush to another, chasing small grasshoppers or other insects.

 

Skinks often rely on speed to avoid predators. All skinks can shed their tails in defence, and the tail re-grows but not to the original length. Skinks can also bite. These are not the deep lacerations inflicted by monitors, but they can cause a good exclamation and cause you to drop them – which is the idea. Blue-tongues can cause considerable pressure and sometimes break the skin.

 

Skinks often lay 1–7 eggs and some, like Cunningham skinks, blue-tongues and shinglebacks, give birth to 1–20 live young. Most skinks mate in spring and lay eggs in early summer or have live young in mid to late summer, sometimes in early autumn. Some skinks have communal egg-laying sites, where numerous females lay eggs in one location.

 

 

 

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Varanidae: monitor lizards or goannas

 

These are the only lizards to have forked tongues. This assists them to forage for food that is often hidden in burrows or under cover. Their sense of smell is like that of a snake, and it helps the lizard to find prey by digging out potential homes.

 

Monitor lizards vary in size from 300 mm to 3 m. They are found in all states except Tasmania. The largest is the Perentie, an arid species that defends a large rocky outcrop as their home site and will then forage around the region for food.

 

Lace monitors are very common across their eastern Australia range and are heavily reliant on large eucalypt forests, especially river red gums, and often use termite mounds in the tree in which to lay eggs.

 

A widespread species seen in rural to arid Australia is the Sand Goanna. This lizard is usually 1 m long, forages in around spinifex clumps, in dunes and around burrows digging up scorpions, lizards and small mammals.

 

All monitors that forage widely will take the opportunity to feed on carrion. This habit is harmful when they feast on road kill. Typically terrestrial monitors use burrows to shelter in, often expanding burrows from other animals. The Yellow-spotted Monitor is a top-end predator that has suffered dramatically from the Cane Toad. Smaller monitors can be found under exfoliating rock outcrops, under bark of small trees or inside hollowed old trees.

 

Lace monitors in particular often forage campgrounds and people can be bold enough to feed them, which is not a good idea. Monitors can be bite and care is essentially so do not leave any bites untreated. All monitors lay eggs usually in burrows these eggs hatch after very long periods from 90–280 days. There is no parental care of young.

 

 

 

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