Tropical Topics A n i n t e r p r e t i v e n e w s l e t t e r f o r t h e t o u r i s m i n d u s t r y Wet tropics lizards No. 33 January 1996 Lizards tell a tale of history Notes from the A prickly forest skink from Cardwell and a prickly forest skink from Cooktown look the same but recent studies of their genetic make-up have Editor revealed hidden differences which tell a tale of history. While mammals and snakes are a The wet tropics contain the remnants Studies of birds, skinks, frogs, geckos fairly rare sight in the rainforests, of tropical rainforests which once and snails as well as some mammals lizards are one of the few types of covered much of Australia. As the revealed genetic breaks at exactly the animal we can be almost certain to climate became drier only the same location. It is thought that a dry see. mountainous regions of the north-east corridor cut through the wet tropics at coast remained constantly moist and this point for hundreds of thousands The wet tropics rainforests have an became the last refuges of Australia’s of years, preventing rainforest animals extraordinarily high number of lizard ancient tropical rainforests. on either side from mixing with each species — at least 14 — which are other at all. This affected not just found nowhere else. Some only However, the area currently occupied individual species but whole occur in very restricted areas such by rainforest has fluctuated. Several communities of plants and animals. as the summit of Bartle Frere, while times as the Earth went through glacial others can be seen throughout the periods, cool, dry conditions caused The presence of two different region. the rainforest to recede into even evolutionary lines within a species smaller and more fragmented patches. which occurs in only a small part of JCU researcher Geordie Torr has This shrinking habitat isolated the world has important implications been studying Boyd’s forest populations of rainforest plant and for the management of the rainforest. dragons in depth for several years animal species from each other. Unable The disappearance of a species, for and has discovered a great deal to mix, populations of the same example the cassowary, from one area about them. He very kindly offered species began to diverge — they may amount to much more than just a to write about them for Tropical began to develop slight differences, ‘local’ extinction. They may have been Topics and decided to share his some to such an extent that they the only representatives of that knowledge of other rainforest became separate species. The population and quite different from lizards with us too. I’d like to thank differences are not necessarily their relatives elsewhere. Their Geordie for all the hard work he has obvious — the two may be disappearance could represent a put into this issue and his mother, indistinguishable from each other from significant loss Eleanor Torr, for the magnificent the outside — but can be detected in of evolutionary illustrations she has produced to their genes. diversity. accompany his text. Researchers studying this focussed mainly on endemic species — those Please note living only in the wet tropics. They that you are welcome to began by taking samples from animals photocopy Tropical Topics. at different sites throughout the However, if the text is region. Genetic analysis of the prickly reproduced separately it must forest skink from various sites in its not be altered and must 275 kilometre range acknowledge the Department of revealed a dramatic Environment and Heritage as the difference between source. Illustrations must not be northern and southern reused without permission. populations. This break Please contact the editor (details occurred at what is termed on the back page) if in doubt. the Black Mountain Barrier, Genetic differences in north-west of Cairns (see populations of prickly Illustration of prickly forest skink by Eleanor Torr map). forest skinks. Harmless snakes of the wet tropics In Tropical Topics 31 we looked at venomous snakes but the majority of snakes encountered in the wet tropics are totally or virtually harmless to humans either because they lack venom or because it is not very toxic and/or the position and size of the fangs makes it difficult for humans to be affected. Pythons do not possess any poison glands. They kill Tree snakes are prey by trapping it with sharp teeth and squeezing it. slim, agile Each time the unfortunate victim breathes out the climbers snake increases the pressure until the prey is most often eventually suffocated. Pythons smell their food with a seen above sensitive flickering tongue and most have a series of the ground. The organs in pits along the jaw which can sense heat, maximum size is two enabling the snake to find warm-blooded animals. metres. Related pythons from overseas have been tested and found capable of detecting temperature The green, or common variations as small as one thirtieth of a degree. tree snake (Dendrelaphis Pythons feed on birds and mammals such as rats, punctulata) and the northern flying foxes, possums and wallabies. Spurs at tree snake (Dendrelaphis each side of the anus in pythons are the calligastra) are very similar and remains of legs, indicating the evolutionary very variable in colour. They are link of all snakes with a lizard-like ancestor. commonly dark above and pale yellowish below but others can be Pythons lay four to 47 eggs which the mother bright green and around Gordonvale protects and incubates by coiling herself there is a sky blue variation. They feed around them, even producing heat by shivering mainly on frogs and lizards. These tree her body. snakes have no venom glands but if cornered might bite. Before doing this Although pythons are non-venomous, if annoyed they inflate the body and neck, they can deliver a nasty bite with their very sharp exposing the startlingly bright blue teeth. skin between the scales. The amethystine python, (Morelia amethistina) also known as the scrub python The brown tree snake (Boiga (above), is Australia’s largest snake, averaging three metres in length but with irregularis) (above) has got venom occasional specimens over seven metres. (The longest recorded, at 8.5 metres, glands but these are connected to was found at Green Hill near Gordonvale.) It is patterned brown and yellow with a fangs at the back of the upper jaw hazy sheen. (‘rear-fanged’) and not considered dangerous. Its most distinctive feature Small amethystine pythons look rather like carpet pythons (Morelia spilota) and is its large amber eyes with vertical spotted (children’s) pythons (Liasis maculosus). However, the scales on the head pupils. It is largely nocturnal, feeding of the amethystine are much bigger than the small scales on the carpet snake’s on small mammals, lizards and birds head. Scales on the spotted python’s head are large at the front, above the eyes, including eggs and nestlings. It but small behind. sometimes turns up in bird cages and in roof spaces. It acts aggressively The water python (Liasis fuscus) is not blotchy like the other pythons mentioned towards humans, holding its body in and is sadly sometimes killed by people who believe it is a dangerous brown tight loops and striking repeatedly, but snake.* It is usually seen near water, where it hunts, and in good light can be is more frightening than dangerous. seen to have a beautiful iridescent sheen. The harmless, non-venomous The slaty grey snake (Stegonotus Filesnakes (Acrochordus sp.) are keelback, or freshwater snake cucullatus) normally forages on the peculiar baggy-skinned snakes with (Tropidonophis mairii) bears an ground for frogs and small mammals. very rough scales which live in water unfortunate resemblance to the Nocturnal, it is often found near water and feed on fish. They are non- dangerous rough-scaled snake and is and near houses and is particularly venomous and reluctant to bite. sometimes killed as a result.* This is active during or after rain. It is dark doubly unfortunate because it is one grey above with a pale belly. Although of the few animals which eats small it can be aggressive it is non- A note on whips cane toads without coming to grief. venomous and harmless, its most A number of whipsnakes This snake is usually some shade of effective defence being the strong (Demansia sp.) are found in the brown and averages half a metre in smell produced from its anal glands. wet tropics. They are slender with length. Each scale is keeled and these large eyes, active by day and very line up to give the skin a ridged Macleay’s water snake (Enhydris speedy. These snakes are appearance. It is often found near polylepis) is a dark brown snake venomous but, on the whole, not water. The keelback has an commonly found in creeks, rivers and considered dangerous. However, interesting ability to shed the end of waterholes, particularly in vegetation some can give a nasty bite and a its tail when under stress, the only by banks. It is a venomous rear-fanged child or someone in poor health Australian snake to perform what is snake but poses more of a threat to could be at some risk if bitten by a quite a common feat among lizards. tadpoles than to humans and is most large specimen. reluctant to bite. *Please remember that all native snakes are protected and it is illegal to kill them. To avoid trouble leave all snakes alone.