Notes fromtheEditor

Page 1: The diverse lizards of OzPage 2: What makes lizards tick?House guests; Frills in the firePage 3: CrocodilesPages 4&5: Lizards in thesavannaPage 6: Questions & answersFacts and stats; Tourist TalkPage 7: Out and aboutPage 8: Bookshelf

Contents:Contents:Contents:Contents:Contents:

No.78No.78No.78No.78No.78June 2003June 2003June 2003June 2003June 2003

Australia has a great diversity of lizards – as many as 47 different species havebeen found living in a single sand dune. Conditions which mammals find soharsh are apparently not such a disadvantage for reptiles.

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Next to Antarctica, Australia is thedriest continent on earth – 75 percentof it is arid or semi-arid. The climate iserratic, with long, irregular dry and wetcycles determined by the effects of ElNino and La Nina. Successful animalsmust cope with unreliable rainfall andprolonged periods of shortages, buttake advantage of unpredictable timesof plenty. In addition, Australia’s soilsare also nutrient-poor with lowproductivity, and fires are frequent.

Energy efficiency is thus the key tolong-term survival. Mammals and birdsgenerate their own heat from food,using up to 90 percent of their energyintake for this purpose. Reptiles,however, tap into the abundant solarenergy to fuel their activities. They arealso much more water efficient (seep. 2). When times are lean, since theydo not need to eat to maintain bodyheat, reptiles can reduce theirmetabolism and go into a state ofsuspended animation for prolongedperiods.

The combination of poor soils and dryclimate is believed to have led to theevolution of plants with tough, thick,chemical-laden leaves and relativelyfew plant-eaters. Instead, thevegetation is broken down by termites,which thrive in Australia, providing anabundant food source for reptiles. Justas mangroves don’t need salt but havedeveloped strategies for living whereno other plants cancompete, so too

have reptiles exploited an environmentlargely uninhabitable for other animals.

The great diversity of reptile speciesmay be due to the long-term stability,and great size, of the Australiancontinent. Those animals which copewell with harsh conditions have hadplenty of time to evolve into differentspecies exploiting different ecologicalniches. This diversity may even befostered by shortages, favouring largenumbers of specialist species whichhave adapted to localised conditionsover fewer, more widely distributedspecies which might have evolved in amore benign environment.

Reptiles have fared much better thanmammals and birds following thearrival of Europeans in Australia.Over 12 percent of mammals havebecome extinct and over 17 percenthave declined, compared with justone possible reptile extinction.Medium-sized mammals weighingbetween 35g and 5.5kg have beenworst affected. During droughts,larger mammals and birds can oftenmove to wetter areas. Smallermammals, however, have probablyalways lived a boom/bust existence –those lucky enough to retreat towetter refuges eventually able torecolonise areas where less fortunateanimals died out. Nowadays, theserefuges attract cattle which competefor the same resources. In addition,rabbits have severely reducedground cover and foxes and feral catsare serious predators. Changed fireregimes also make life difficult formany mammals and birds. Reptilesseem more resilient to the samepressures.

I would like to thank Russell Best,Queensland Parks and WildlifeService, and Tony Griffiths, KeyCentre for Tropical WildlifeManagement, Northern TerritoryUniversity, for their help with thisissue.

Next to birds, lizards are amongthe most commonly encounteredvertebrate animals in thesavannas. Indeed, the diversity oflizards in the tropical savannas isparticularly rich, exploitingnumerous habitats fromwoodlands to sandstoneescarpments, rainforests andsemi-arid zones, many endemic tojust small areas. This TropicalTopics looks at some of the morewidespread and common species.

This issue also looks atcrocodiles. Although not lizards,they are lizard-like in manyrespects and are importantreptiles of the savannawaterways. Visitors to tropicalAustralia must always be aware –and beware – of these fascinatingbut potentially dangerousanimals.

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Lizards are efficient creatures. Instead of consuming food togenerate energy, most use solar power, basking in sunshine orsleeping in a warm spot to power up their ‘batteries’ for theday’s (or night’s) activities. Some lizards, such as dragons, areable to raise their ribs and angle their bodies to increase thebody surface exposed and can become darker to absorb moreheat. This strategy, known as active thermoregulating, is notan option for some lizards which live in closed forests.Instead, they thermoregulate passively, or ‘thermoconform’,their body temperature simply conforming to that of the airaround them.

Lizards are also efficient users of water. Their dry scaly skinreduces moisture loss, those living in the hottest areastending to have compact bodies to minimise loss and/orrestricting most activities to hours of darkness. In addition,reptiles do not use water to flush nitrogenous wastes from thebody as urine, like mammals do, but convert them to a formwhich can be dumped as solid dung.

Fires are common in savanna woodlands so how do theyaffect the frilled lizards which live there? Researchers foundthat, on the whole, fires benefited these lizards, mainly byremoving ground cover and allowing them a better view ofpotential prey. However, different types of fires have differenteffects. Fires occurring early in the dry season are less intenseand do not seem to threaten the frilled lizards, which avoidthem by staying in tree canopies. Late dry season fires, on theother hand, are much more dangerous killing up to 30 percentof the lizards. Many of those studied chose to leave theirtreetop retreats and seek shelter in termite mounds – asuccessful strategy which saved their lives. Many, however,stayed in the trees which was much more hazardous.

Nonetheless, areas burnt by late dry season fires seem toprovide more food for frilled lizards. Generally, abundance ofinvertebrates in the lizards’ stomachs decreases – termites bymore than 40 percent – but there is an increase in numbers ofants, which seem more active and abundant in burnt areas.Importantly, however, the lack of vegetation cover means thatthe lizards can find more, and larger, prey.

When compared, frilled lizards from areas unburnt for manyyears were not in as good condition as those from regularlyburnt areas; areas unburnt for prolonged periods tended tohave low populations of frilled lizards. On the whole, areaswhich are burnt regularly in the early dry season are mostlikely to benefit these lizards byincreasing food supplies but notthreatening the animals’ lives.Although late season fires seemto provide more food, they alsokill off such a large proportion ofthe lizards that the population isunlikely to be sustainable ifsuch fires are too frequent.Only if increased foodsupplies attract sufficientnumbers of lizards fromneighbouring unburntareas would the populationremain viable.

Geckos are among themost familiar oftropical animals,living in our houses,scuttling around our ceilings, swarming around our outsidelights to pounce on dazzled insects and conducting theiraffairs behind our picture frames.

Several species of geckos qualify as ‘house’ geckos, havingadopted humans as co-habiters. The dubious dtella (Gehyradubia) is found widely in Queensland and northern NewSouth Wales. Varying in colour from pale pinkish to brownwith darker markings, it can also be found in the wild on treesand in rock crevices.

Another species, the house gecko (Hemidactylus frenatus) isan import from Asia which has hitched a lift with travellinghumans. It is now found at the tip of Cape York Peninsula, inurban areas like Cairns and in the Northern Territory where itis spreading from Darwin to settlements along the road southtowards Alice Springs. It seems to be dependent on humanhabitation. This gecko can change colour, becoming pale atnight and dark during the day. Although similar in appearanceto the dubious dtella it can be distinguished by its slightlyspiny tail. It also has a distinctive loud scolding call; nativehouse geckos make only a soft chattering call.

The nocturnal lifestyle of geckos prevents them from baskingin the sun as most lizards do to raise their body temperatures.Instead, they choose daytime retreats which are warmed bythe sun, particularly in the afternoon, so that they are full of

energy by sunset.Competition forsuitable spots canbe fierce, leadingto fights betweenopponents duringwhich they graspeach others’ tailsin their mouths.

Geckos, legless lizards and skinks will readily drop their tailswhen threatened, the wriggling appendage serving as adistraction while the owner makes its getaway. Fracture planesbetween certain vertebrae at the top of the tail allow it todetach easily when pulled apart by special muscles. Thissacrificial offering is easily regrown. Tails of dragons andgoannas can also break off, but do not do so as readily andtend not to regrow.

All dragons, goannas and Australian geckos lay eggs butsome skinks give birth to live young. Viviparity, as this isknown, is more common in cool-climate reptiles, perhapsbecause the warmer temperatures inside the mother’s bodylead to better development of the young.

Most lizards are silent, but geckos chatter and squawk, somespecies making the characteristic and sometimes startling‘gecko’ call which has given them their name. Legless lizardsmay make a high-pitched squeak and some skinks produce asoft squeak.

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Medical researchers are intrigued byhow a gecko is able to grow a new tailwithout the fluid retention and swelling(lymphoedema) frequently associatedwith radical human surgery. The keyseems to be a potent protein growthfactor, discovered in geckos, whichenables them to regenerate theirlymphatic systems. It is hoped a similarproduct can be developed for humans.

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CrocodilesCrocodilesCrocodilesCrocodilesCrocodiles

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Croc origins

All vertebrates evolved from reptiles, which in turn developedfrom amphibians. However, the branch on the evolutionarytree which was to become lizards and snakes diverged fromthe branch which would give rise to birds, dinosaurs andcrocodiles more than 300 million years ago. Interestingly,birds, dinosaurs and crocodiles all developed the samearrangement for the joining leg and foot at the ankle. Thisconnection in lizard legs is quite different.

Nonetheless, crocodiles share many characteristics withlizards. For example, they bask in the sun to raise their bodytemperature, lying sideways to give maximum exposure to theblood-rich bumpy scales which act as solar panels on theirbacks.

As with lizards, crocodiles can go without food for longperiods. If a crocodile’s body temperature drops too much,

Big-hearted crocsCrocodiles have four-chambered hearts, like mammals andbirds, whereas all other reptile hearts have three chambers.This difference in structure ensures that the blood flowsystem in crocodiles is more efficient. In addition,crocodiles can control the flow of blood throughout theirbodies by increasing or decreasing the heart rate or by‘shunting’ the blood flow to areas of importance such asthe heart, brain and muscles and restricting the flow to non-essential areas like the intestines. However, some reptilianfeatures allow oxygenated and deoxygenated blood to mix,an advantage for a crocodile when diving.

digestive enzymes cannot work and food rots in the stomachinstead. Both species decrease their food intake during thecooler months, and in more southern locations crocodiles maycease feeding altogether during winter. The growth ofcrocodiles during the cooler months decreases.

Be croc wise in croc countryDon’t make a croc an offer it can’t resist.• Obey crocodile warning signs, even if you can’t see crocodiles.• Don’t go swimming or paddling in areas where crocodiles live.• Keep well away from the water’s edge.• Don’t gut fish, discard food scraps or wash dishes at the water’s edge.• Don’t camp within 50m of water.• Be careful in boats; don’t hang a foot over the edge.• Don’t sit in branches above the water – crocs can jump.• Supervise children and be moderate with alcohol intake in croc country – many victims of crocodile attacks had become careless when intoxicated.

Estuarine crocodile (Crocodylus porosus)

This crocodile isfound not just in Australia but also inSouth-east Asia, India and around western Pacific islands. Itis sometimes called the saltwater crocodile, but this is adeceptive name because these animals are found not just onthe coast (and occasionally in the open sea) but also farupstream and in many freshwater swamps and billabongs.Almost any body of water in tropical Australia must besuspected of harbouring crocodiles of at least one species.

Young estuarine crocodiles feed on insects, crabs, prawnsand shrimps, but as they grow in size the amount of vertebratematerial in the diet increases. Larger animals attack sea turtles,goannas, wallabies, pigs and even cattle; estuarine crocodilesover 3m in length are a danger to people. Very strong musclesare employed for closing the jaws, which can easily crush apig’s skull – but a rubber band around the snout of a 2mcrocodile is enough to keep it from using its weak ‘opening’muscles. Prey, grabbed in the jaws, is usually drowned.Contrary to popular myth, crocodiles do not store uneatenfood and most certainly do not prefer rotten food.

Adult maleestuarinecrocodiles areusually between3.3m and 4.5m, butlarger individualsover 6m have beenrecorded.Females grow toabout 3 to 3.5mlong.

There are about 23 species of crocodilians in the world, two of them in Australia.

Freshwater crocodile (Crocodylus johnstoni)

This species is found only in Australia. It inhabitsfreshwater rivers, swamps and billabongs throughoutnorthern tropical Australia from Broome in Western Australiato Princess Charlotte Bay in Queensland – but no furthersouth on the east coast except where it has been introducedartificially. It does occur in tidal estuaries, but tends to avoidareas inhabited by estuarine crocodiles, which sometimes eatfreshies. This species is much smaller than the estuarinecrocodile, males growing to about 2m in length – although a3m male has been caught – and females to about 1.8m.

Freshwater crocodiles feed on fish, insects, crustaceans, smallbirds, reptiles and frogs, often grasping them with the tip ofthe jaw and manoeuvring them further into the mouth. Theydo not prey on people but will bite in self-defence. Since somelarge freshies take wallabies, children should always besupervised near freshwater crocodiles.

Telling the differenceThe best way to tell the two Australiancrocodile species apart is to lookat the skull and jaws.The skull of anestuarine crocodile(above) is broad andthe jawline is irregular, whereas the skullof a freshie (right) isnarrower and thejawline straighter.

Croc typesCroc typesCroc typesCroc typesCroc types

Although they look similar, crocodiles and lizards have a very different ancestry.

Dragons (Family Agamidae)There are about 60 species of dragon lizards in Australia (330 worldwide). They are active during the day, although some in hotarid zones may come out at night. With well-developed limbs they are good runners, climbers and, in some cases, swimmers.Dragons are able to change colour, becoming dark when absorbing heat and lighter when trying to cool down. Males becomemore colourful at mating time.

The frilled lizard (Chlamydosaurus kingii), found throughout the forests andwoodlands of northern Australia, is the only lizard in the world with a frill – a thinbut wide, scaly ruff. When not in use, it is folded loosely over the lizard’s upperbody, but when the animal is called upon to defend itself, it opens its mouth tounfurl the frill into a circular ruff which would have been the pride of an Elizabethancourtier. Although the frilled lizard is coloured with muted tones of browns andblack which camouflage it well in its dry woodland home, the frill, when erect, isbrightly coloured with patches of yellow and orange. Its owner is now aiming to beseen and with mouth gaping, it lashes its wiry tail at the enemy. If bluff fails, thelizard takes off, running along the ground on its hind legs to the nearest tree.Although probably primarily used in defence, the frill, which has numerous bloodvessels, may also help with temperature regulation.

The frilled lizard spends 90 percent of its time in the trees. It is a ‘sit-and-wait’predator which surveys the ground, leaping on food such as ants, termites and

other invertebrates when they show themselves.Studies have shown that in the dry season whenfood is scarce, a frilled lizard will climb up into thecanopy of a tree and stay there for up to threemonths as its metabolism drops by as much as 70

percent. The lizard is aestivating – the equivalent, ina hot climate, of hibernation. By dropping its energy

requirements, it can thus survive a period of foodshortage. To lower its metabolism rates the lizardmust also keep cool so, instead of basking inthe sun it keeps in the shade, shifting around

the trunk of the tree if necessary to avoid thesun.

This impressive lizard is one of Australia’slargest dragons, growing to 95cm in total

length.

Gilbert’sdragon orGilbert’slashtail(Lophognathusgilberti) is acommon andrelatively largelizard (52cmtotal length) with a long thin tail almostthree times the length of the head andbody combined. It is found across thesavannas, except in eastern Cape YorkPeninsula. Often seen in pairs, somemales have a white streak on the side ofthe head. It likes to perch on anyelevated object – trees, termite mounds,posts and so on – especially near water.It feeds on ants and any other lizardwhich it can subdue.

Two-lined dragons live on the ground orin low vegetation. They are named forthe two pale lines along their backs.There are several species, but thenorthern two-lined dragon (Diporiphorabilineata) is one of the mostwidespread, found across northernQueensland and the Northern Territory.It lives in savanna woodland,sclerophyll forests and sandy country.Well camouflaged, it perches on lowbranches, looking out for insects toambush.

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Goannas (Family Varanidae)Goannas tend to be large lizards (although the pygmy goanna of the central deserts is, at 25cm total length, the smallest goannain the world). They are also among the oldest; early versions were around to see the dinosaurs and even the modern versionsdating back 15-20 million years. Although found elsewhere, Australia has the lion’s share of goanna species with about 25 ofthe world’s 30. Thought to be the most intelligent of lizards, they eat a variety of other animals, both living and dead, includingother reptiles, insects, baby birds and mammals, including possums. At home on the ground and in trees, they constantly flicktheir forked tongues, picking up scent particles from the air and transferring them to a structure known as the Jacobson’s organ,on the roof of the mouth, where they are interpreted.

The spotted tree monitor (Varanus scalaris) is found acrossthe northern tropics almost anywhere there are trees, darkerindividuals inhabiting rainforest and lighter ones in drierareas. The varied patterns of this species tend to match localtree trunk colours but most have spots of some sort, usuallypale with a dark centre. This lizard hunts on the ground as wellas in the trees, but if disturbed on the ground, will beat ahasty and noisy retreat up the nearest tree, disappearing intoa hollow or keeping on the opposite side to its pursuer. It

feeds on insects,smaller lizards

and babybirds and may

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to prey.

Gould’s goanna (Varanus gouldii) is found in most parts ofcontinental Australia, although it tends to prefer sandy areasand avoids rainforest. Reaching 1.5m in total length, andweighing several kilos, Gould’s goanna is black with varyingamounts of yellow. It is at home on the ground, rarely climbingtrees, as it seeks prey of many types – insects, lizards andtheir eggs, and smallmammals – andscavenges for carrion.It digs holes or usestree logs or other animals’burrows as retreats. Eggs are laidin a deep burrow which is thenclosed and concealed by thefemale.

Spotted tree monitor illustration by Eleanor Torr644444

Bynoe’s gecko (Heteronotia binoei) isvery common throughout most of theAustralian mainland. Also known as theprickly gecko because of its bumpy skin,it thrives in all types of habitat fromforests and woodlands to arid areas. Itshelters in crevices, under logs and inrocks, but at night searches openground for insects – and other geckos.These geckos sometimes lay eggs incommunal nests which may contain upto 150 eggs.

Geckos (Family Gekkonidae)There are more than 90 gecko species in Australia, most of them under 20cm in total length. These are nocturnal lizards althoughthey may be active in dark places during the day. They feed only on prey which moves, such as insects and smaller geckos. Agecko’s eyes are permanently covered with a transparent eyelid, perhaps to reduce evaporation. Unable to clean its eyes withtears, the gecko licks them with its tongue. Some gecko species are parthenogenic, meaning that the females can produceoffspring without male input.

The major skink (Egernia frerei) is found along the eastcoast of Queensland to the New South Wales border and inArnhem Land, patterns and colouring varying according tolocation. It is a large skink, up to 39cm in total body length,thickset and generally glossy brown, and can be seen sunningitself at the edge of open forest or rainforest. It eats insects,snails, other lizards and vegetable material and lives in small

communities in complex burrow systems.

The related and similar, butconfusingly namedEgernia major iscommonly knownas the land mullet.It is found in

south-eastQueensland and

northern New South Wales.

Skinks (Family Scincidae)These are the most numerous of lizards with 1300 species in the world and about 300 species in Australia, found in allenvironments. They tend to be smooth and usually glossy. Most eat insects, some eat other lizards and others eat fruits,flowers, leaves and fungi.

More than 30 of thegecko speciesfound in Australiabelong to theDiplodactylus genus. The fat-taileddiplodactylus (Diplodactylusconspicillatus) is found only on theground in stony and grassy areasacross much of the top of Australia, itscolour varying to match the habitat inwhich it lives. About 10cm in totallength, it has a bulbous tail which actsas a fat storage organ, and feeds ontermites and other insects.

The fat-tailed diplodactylus spends itsdays in underground holes such asabandoned burrows of trap-doorspiders, blocking the entrance with itsfat tail to keep out predators and keep inmoisture. It is sometimes called theburrow-plug gecko. Most adults havelost their original tails which arereplaced with more rounded ones whichmake even better burrow-plugs.

The spiny-tailed gecko (Diplodactylusciliaris) is found in woodlands andgrasslands, westwards from westernQueensland, living in trees or othervegetation. It is also frequently seen onroads. This is one of 10 ‘tail-squirting’species. It can eject an offensive andsticky liquid from the spines of its tail.By lifting its tail it can aim the fluidaccurately up to a distance of 30cm. Thisgecko is also particularly good atchanging colour from dark to very pale.

Legless lizards (Family Pygopodidae)Legless lizards are quite closely related to geckos, sharing many characteristics.They occur only in Australasia with 33 of the 35 species restricted to Australia andtwo found also in New Guinea.They are sometimes called flap-footed lizardsbecause, while they lack forelimbs entirely, they still have a scaly flap where thehind legs once were. Their loss would probably have enabled these lizards to fitbetter into small spaces in vegetation and rock crevices and to burrow in soil. Theyare also called snake-lizards due to their obvious resemblance. However, they havebroad, flat tongues, not forked ones, and move with more regular curvingmovements. They stay out of sight most of the time, basking in upper layers of leaflitter and soil and moving in the open only at night if possible.

Burton’s snake-lizard (Lialis burtonis) is the most widely distributed of the leglesslizards, living in most habitats except for rainforest. It can grow to 62cm in totallength. It has a long, pointed head, quite unlike any snake’s, and is very variable incolour, even within populations in small areas. Although most legless lizards eatinsects, this species feeds almost exclusively on otherlizards, ambushing them when they come close.It can swallow a lizard with a girth greaterthan its own. It is active by day andnight, but prefers to keep out ofsight by day and tends to benocturnal in hotter regions.

Major skink

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The common bluetongue lizard (Tiliqua scincoides) at 56cmtotal length, is one of the world’s largest skinks. It is foundacross the northern tropics (but not in rainforest) and alongthe eastern and south-eastern part of the continent. It is athickset lizard with small legs and a more-or-less banded backwhich varies according to location. It can be active on warmnights as well as during the day, and eats insects, snails andvegetable material such as fruits. When alarmed this skinkopens its pink mouth, hisses, and sticks out a dark bluetongue inwarning. Ifthis isignored, it can deliver apainful bite. Generally slow-moving, it can move rapidly ifnecessary. There are severalspecies of bluetongues, all ofwhich give birth to live young.

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FFFFFacacacacacts and stats and stats and stats and stats and statststststsQ Is it true that predator birds, suchas crows and hawks, will carry a liveember from burnt bush to start newfires elsewhere, so increasing theirhunting opportunities?

A Black kites are sometimes called ‘firehawks’ because they collect in largenumbers above fires, looking forinsects, small mammals and reptilesfleeing from the blaze. The idea thatthey also actively spread fires is oftenrepeated. I have been unable to findanyone who has actually seen this butam assured that it has been observedby reliable naturalists in the NorthernTerritory and that it has also beenreported from Africa – black kites are awidespread species.

Dr Penny Olsen of the AustralianNational University wrote in responseto this query: “I have heard it butimagine it’s likely that the kite grabssome poor creature fleeing the flamesand in doing so gets a fistful ofburning grass or whatever, which itthen drops. However, black kites havelearnt to drop chips into water to ‘fish’,so who knows?”

If any readers have personally seenthis behaviour, I would be glad toknow about it (editor).

Crows are very clever birds, thoughwhether they too are arsonists isthought unlikely. Certainly they areadept at using and even creating tools,though. A captive New Caledoniancrow was observed bending a piece ofwire to make a hook to retrieve food,repeating this many times. For moredetails about this see the website://news.nationalgeographic.com/news/2002/08/0808_020808_crow.html

Q How many species of Eucalyptusare now Corymbia and is there a list ofthem with descriptions? Why werethey changed? Can you suggest whereto get scientific names?

A In 1995, all bloodwoods and ghostgums were given their own genus,Corymbia. A genus is a category forgrouping together species which havedescended from one ancestor and, as aresult, are closely related. However,differences in the DNA as well as otherstructural differences, such as leafanatomy and flower structure, showedthat there were actually two groupswithin Eucalyptus, which is why thechange was made.

Nevertheless, Corymbia are still giventhe common name eucalypt. Initially113 species were included, but a fewmore have since been added so thetotal is currently about 130. Thisnumber will change as more species aredescribed.

The decision to separate Corymbiawas published by botanists LaurieJohnson and Ken Hill in Telopea 6(2-3), a journal issued by the RoyalBotanic Gardens, Sydney. Ian Brooker,author of Eucalypts of Australia (threevolumes) does not agree and does notinclude the name Corymbia in hisbooks. Appendix 4 of Hill andJohnson’s paper gives a table whichshows how the names used by Brookercorrespond to Corymbia. However, itmay no longer be in print. A list ofQueensland Corymbia species can befound in Names and Distribution ofQueensland Plants, Algae andLichens, a Queensland Herbariumpublication.Acknowledgements to John Clarkson,Queensland Parks and Wildlife Service.

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There are about 6400 reptiles in the worldwith roughly 700 in Australia. These includesnakes, lizards, turtles and crocodiles.

Goannas are also known as monitor lizards.Varanus, their scientific family name, comesfrom the Arabic word for monitor becausethese lizards had a reputation for warningof the approach of a crocodile – they weremonitoring the situation. The word‘goanna’, used only in Australia, is derivedfrom the Spanish word ‘iguana’, originallyused for large American lizards.

A 5.5m long Megalania, a goanna withancient origins, was present in easternAustralia as recently as 30,000 years agoand would have crossed paths withAboriginal settlers.

Largest Australian skink status is claimedfor both the land mullet at 58cm total lengthand the common bluetongue at 56cm totallength. Largest dragons are the easternwater dragon and the frilled lizard, bothgrowing to about 95cm total length.

The largest Australian goanna is thedesert-dwelling perentie which can growto 2.5m in total length but it is dwarfed bythe massive Indonesian Komodo dragon,another goanna which reaches lengths of3m and can weigh as much as 250kg.

Some geckos are able to perform gravity-defying feats, walking on ceilings and onpanes of glass, thanks to numerous littlehooked bristles on the soles of their feetwhich give them an astonishing grip.Scientists in California are hoping toproduce synthetic versions which couldbe used to improve shoes for athletes andtyres – and perhaps make ceiling-paintingeasier!

No Australian lizards are venomous. Theonly venomous lizards in the world are theGila monster and bearded lizard of northAmerica.

Geckos must be on guard againstinadvertently sharing their hidey-holeswith predatory snakes but tests withLesueur’s velvet gecko, found in south-east Queensland and coastal New SouthWales, have shown they are able to notonly detect the odour of a snake, butdistinguish potential predators fromharmless snake species.

The smallest lizards in the world grow tojust 16mm from snout to vent – scarcelylong enough to stretch across a 10 centcoin. Two related species of geckos, theylive on islands in the Dominican Republicand the British Virgin Islands.

Out and aboutOut and aboutOut and aboutOut and aboutOut and aboutLook out forfreshwater jellyfish.Although not exactlywell-known, thesecreatures have beenfound in most parts of the world and inevery Australian state except Tasmania.James Cook University researcher, Lisa-ann Gershwin, is keen to find out howwidespread they are. They are likely tobe found across the tropics, in any calmwater bodies such as dams, fish ponds,shallow pools and slow-flowingwaterways.

Restricted to fresh water, the jellyfishare white or colourless, delicate and lacyand about the size of a 5 or 10 cent coin.They are probably found all year intropical areas often appearing in largenumbers when they can look like driftingsnowflakes in the water. They then tendto disappear within months or justweeks, not appearing again for maybe5–10 years. It is possible they aretransported on the feet of waterbirds.

These jellyfish eat small aquaticinvertebrates, including mosquito larvaeand are thus a potentially importantmosquito control.They may have a mildsting, but this isthought to only affectpeople with verysensitive skin.

If you come acrossthese animals,Lisa-ann Gershwin would love to hearfrom you. You can contact her byphone: 4781 6446, or email:lisa.gershwin@jcu.edu.au There is anAmerican website on freshwater jellies:nsm1.nsm.iup.edu/tpeard/thing.htm

Caesalpinia bonduc is a prickly vineknown as nicker nut and also as wait-a-while, although it is quite different fromthe scrambling, thorny rainforest palm ofthat name. It grows in monsoon vinethickets mainly near the coast, althoughit can also be found quite far inland,possibly where seeds have beenaccidentally carried. Because the seedscan float, and remain viable in salt waterfor several years, these plants are foundin coastal regions throughout thePacific, Asia and even America.

Scrambling or climbing to a height of 3mor more, this legume has yellowpeaflowers which are followed duringthe dry season by oval, slightly heart-shaped, brown, woody seed capsuleswhich are covered in dense spines.These open to drop rounded dull, olive-green seeds which resemble animaldroppings or balls of plasticine ratherthan seeds. They are collected by greatbowerbirds.

Brilliant red flowers appear on coraltrees (Erythrina variegata) during thedry season, usually sprouting from barebranches, the tree having temporarilylost its leaves. Rich in nectar, thesepeaflowers are popular with birds suchas honeyeaters. The stems andbranches are covered with small blackprickles which tend to become longerwhen the tree is subjected to waterstress but dropping off as the stemsenlarge.

This tree is found in open forest andwoodland often on shallow, gravellysoils and behind the beaches. It is also anative of India, Malaysia and Burma.With seeds which can float in salt water,it has been able to spread by sea. InAsia, this tree is put to a number ofagricultural uses – leaves provide agood fodder for stock and the wood isused for fences, light packing boxes,paper pulp and fuel. Its deciduous habitis put to good use by farmers who usethe trees to support pepper, vanilla,betel and yam vines which need shadeduring the hot wet season, butappreciate sunshine in the cool, dryseason.

Male great bowerbirds are busy aroundtheir bowers from April until Novemberor December, emitting harsh, raspingcalls and hoping to attract females.Found throughout the northernsavannas, these birds can be verynumerous in the denser woodlands,particularly near water. The male’sbower is a dense avenue of uprighttwigs arranged in parallel, curving walls.It is decorated with white stones andshells and green fruits, glass and so on.The male tends to rebuild his bowereach year, often next to the old one.After mating the female goes off to nestand raise the young on her own whilethe male continues to attend the bower,hoping to attract more partners.

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inRecently a ranger in Cape Tribulation,in north Queensland, discovered atourist bus stopped on the road in thevicinity of Noah Creek with its hazardlights flashing. Passengers hadalighted and were standing around asub-adult cassowary. Cassowaries arelarge, unpredictable and potentiallydangerous birds – people should notapproach them. In this case the touroperator did not seem concerned thathe was putting his passengers at risk.More vehicles stopped and soon theroad was blocked in both directions aspeople wandered around a veryconfused cassowary.

We all love to see a cassowary but thechances are strong that this particularbird will be next seen dead on the road.For the safety of both cassowaries andpeople, these animals should not beapproached and should never beencouraged near roads.

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Woodswallowsare among themany nomadicbirds of the savannaswhich moveaccording to foodsupplies.White-browedwoodswallowsmayappear in flocks of 100 or more,following locust swarms. They tend tomove north in winter, returning south inspring and summer and nesting whenconditions are good, thus takingadvantage of the unpredictableAustralian conditions.

White-breasted woodswallows alsotend to move north in winter, arriving inlarge numbers to feed on grasshoppersand other insects. They are usually seenhigh in the sky around sunset catchingmoths in flight. These birds are seldomfound far from water and have anendearing habit of sitting side by side,snuggling together in groups andpreening each other.Acknowledgements to StuartTraynor

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Stella MartinThe EditorTropical TopicsEnvironmental Protection AgencyPO Box 2066(5B Sheridan St)CAIRNS QLD 4870Ph: (07) 4046 6674Fax: (07) 4046 6751e-mail: Stella.Martin@epa.qld.gov.au

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This newsletter was produced by the Environmental Protection AgencyThis newsletter was produced by the Environmental Protection AgencyThis newsletter was produced by the Environmental Protection AgencyThis newsletter was produced by the Environmental Protection AgencyThis newsletter was produced by the Environmental Protection Agency with funding from the Cooperative Research Centre (CRC) for Tropical Savannas with funding from the Cooperative Research Centre (CRC) for Tropical Savannas with funding from the Cooperative Research Centre (CRC) for Tropical Savannas with funding from the Cooperative Research Centre (CRC) for Tropical Savannas with funding from the Cooperative Research Centre (CRC) for Tropical SavannasManagement.Management.Management.Management.Management.

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Opinions expressed in TropicalTopics are not necessarily thoseof the Environmental ProtectionAgency.While all efforts have been madeto verify facts, the EnvironmentalProtection Agency takes noresponsibility for the accuracy ofinformation supplied in TropicalTopics.© The State of Queensland.Environmental Protection Agency2003.

Tropical Savannas CRCNorthern Territory UniversityDARWIN NT 0909Ph: (08) 8946 6834

Orange (savanna) issues of TropicalTopics (nos. 64, 68, 71, 73 & 75) can befound on the CRC for TropicalSavannas Management website:savanna.ntu.edu.au/publications/tropical_topics.html

Reptiles and Amphibians of AustraliaHarold G. CoggerReed New Holland, Sydney (2000)

This is the standard reference book forAustralian reptiles.

Encyclopedia of Australian Animals:ReptilesHarald EhmannAngus & Robertson, Pymble (1992)

Each species has a brief descriptionplus interesting information on specialfeatures and behaviour. There are alsophotos and distribution maps as wellas a good introduction.

Australian Tropical Reptiles andFrogsClifford and Dawn FrithFrith and Frith Books, Malanda (1991)

Australian Crocodiles: A NaturalHistoryGrahame Webb and Charlie ManolisReed New Holland, Sydney (1998)

This extremely informative book looksat all aspects of crocodiles.

Lizards of AustraliaStephen SwansonAngus & Robertson, North Ryde(1990)

Forty Queensland LizardsFloyd D. DaleQueensland Museum, Brisbane (1973)

Nature Australia Vol 27 No 6 Spring2002Goannas, first-class monitorsSteve van Dyck

Australian Journal of Ecology (1996)21, 386-398The effects of fire on the frillnecklizard (Chlamydosaurus kingii) innorthern AustraliaA.D.Griffiths and K.A. Christian

The Future EatersTim FlanneryReed New Holland, Sydney (1997)

Tim Flannery’s famous book looks atdiversity and extinctions, among manyother things.

Nature Australia Vol 26 No 5 Winter1999Home GeckonomicsSharon Downes

This article is about Lesueur’s velvetgecko.