gecko

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This attractive little creature is sometimes on sale at Melbourne assorted reptile pet shops. They are fairly low in cost and are rather unpopular. The reason for this disparity is because these little reptiles are strictly nocturnal and the store enclosures always look empty. This is because they are hiding! They are pathologically shy of light and will only emerge from their shelter when it is nearly dark to hunt. They will live up to five years and do not appear to stop growing. Color and skin markings differ from allmost completely black to a light brown, sometimes with distinctive orange bands. The camoflage pattern is superb, they are allmost invisible against coarse tree bark. The eyes have a beautiful golden metallic sheen.

Housing the gecko.
The geckos' foot pad is a miracle of nano molecular materials engineering. The laminae on the pads terminate in monomolecular filaments and are attractive to nearly all surfaces by molecular van-der-vaals forces. The attractive power of a gecko footpad, if all micro hairs were engaged to the surface has an attractive force estimated at over 10000kgs per square centimetre. This is better than super glue. The gecko foot pad is the reason that your enclosure must be fully enclosed. It is an amazing thing to watch a gecko run up a shear piece of polished glass and even hunt when suspended upside down against glass. (watch...the footpad will not stick to teflon, we have tried this at home!) The ventilation holes must be numerous and if there is any hole larger than 5mm they WILL escape.

The southern marbled gecko ranges into southern Victoria and seems to be able to cope with the cold weather. In the wild it inhabits rock creavices and tree bark where it coexists with very substantial size spiders . At sun down they emerge to hunt, warming themselves on the absorbed heat of the rock or tree surface that has been facing the sun. They will hunt, get cold, return to a basking position and continue hunting until the basking spot cools. In Melbourne this mean on a typical day they have about an hour to get a meal before they return to hide out the night. Your enclosure should be facing sun, but behind shade cloth, else they will get cooked on a hot sunny day. Put large rocks in the enclosure and this will help stabilise the temperature and make them feel at home. One cubic foot of volume will happily house up to 6 adult geckos without rancor.

The enclosure should be glass, to help you keep it clean, as they will foul the sides during their nocturnal hunt. The floor should be perspex for safety and resilience. The lid should be heavy or firmly attached and must be well ventilated. The gecko is very shy and must have good hiding places or it will become distressed and not thrive. Bind together layers of tree bark, they love this as it mimics their true habitat. The floor of the enclosure should be a mixture of coarse sand and small stones. They will lay their eggs into the sand during breeding season. Include small rocks for visual appeal and temperature stability. During the winter months it is good to gently heat the enclosure. I biult into a die cast box a ten watt resistor and it gets powered from a plug pack to provide an average power of ten to fifteen watts. The geckos will bask on this to warm up during their evening hunt. This is not needed in summer months, but they do appreciate it when it gets cold.

When you change the sand in the enclosure be on the carefully lookout for eggs which the female will bury one centimeter below the surface. The eggs are about 1.5cm long and pure white. The eggs will hatch in about ten weeks. A live egg will be slightly opaque and heavy, a dead egg will bleach and be very light to the touch as its insides evaporate. Return the eggs to the same aspect where you found them, the female has selected the spot for its average temperature. The female does not appear to form a long term attachment to the egg site.

Feeding the gecko.
I am note sure what they actually eat in the wild. I suspect it is mainly small spiders. They have ignored most garden insects I have offered them. The one insect they will eat are the small crickets sold by reptile shops. If they are really hungry and dont see you watching them they will actively hunt them in diffuse daylight. The right diet seems to be about one cricket per day but this does depend on the season and the temperature. I am not sure about meal worms, I have tried them but I have not actually seen them being eaten. You also need to look after your crickets, they are living creatures too. Like most other reptiles, their appetite declines in the cold season, so dont worry if they seem to have gone off their food.

I was not sure how to feed hatchlings. They have been uninterested in the smallest crickets they were offered. After two weeks we returned them to a pile of bricks from where their parents were captured. We found them grown up six months later. They had to deal with hungry birds, ravenous spiders and other challenges. They were able to find their own dinner, which I think could have been small spiders and springtails, small shrimp like creatures that live under decaying vegetation. Now , we do know. They will not eat for about two weeks after hatching, after that they will accept "small crickets".

I have observed with a microscope the dung of the wild woodpile geckos. Their natural diet appears to consist of spiders (fangs), small beetles (wing cases)...probably cockroach nymphs and some evidence of flys (fly wings).

Our latest hatchlings have now taught us how to feed them. Do nothing, leave them in their own private enclosure where they can learn to hunt small crickets. They appear to show no interest in hunting for about 2 weeks, but naturally they must have fresh water. They must have a private enclosure as the adults will deprive them of food. They will grow very rapidly with a private food supply. Leave a teaspoon of rolled oats in their private enclosure, this will keep the small crickets alive until eaten.

It is natural to assume the gecko gets its water requirement from its prey but even so, always provide them with a shallow container of fresh water. I have now seen a gecko deliberately drink , they will lick the surface of the water with their long tongues. It is very rare to see this and I have only seen it once in the last 3 years.

The academic paper from "Greer, A.E. 2006. Encyclopedia of Australian Reptiles. Australian Museum Online", suggests that they take fruit flies and small house flies but I have yet to see this. My problem with this is capturing and then introducing flying insects into a practical gecko enclosure. There are certainly less flies around Melbournes' suburbia compared when I was young and actually finding a fly to capture cannot be done "on demand".

handling the gecko.
This Gecko is a very shy creature. Avoid handling it to avoid distress. A distressed gecko will shed its tail quite readily. When you do need to handle it have a darkened container to transport it or to temporarily store it while you muck out its enclosure. I have had some geckos actually become finger tame but that is exceptional. A gecko that has shed its tail will regenerate it in about 8 months. Most geckos that I have observed outside have regenerated tails so it appears to happen often in their little lives. If your gecko does shed its tail, leave it with the animal. It is said they will eat it, allthough I have never observed this. I have found the most effective way to capture a gecko is to goad it into a black painted container which it will happily enter. If you must pick it up , cup your hands to make a dark cavity and do not apply pressure. Put it in a darkened container immediately. It will remain calm in the dark.

Some geckos are very aggressive and will rear up and strike you as would a snake. These more aggressive specimens generally dont have regenerated tails ! Our favorite gecko "Grump" is a girl, very large for a Christinus marmoratus, and pretends it is a deadly snake ! The gecko will move with great speed and agility and will dive into the air to escape you. Recapturing an escaped gecko is extremely difficult, they are not afraid of heights, sheer walls or the dark. Dont loose it, you will probably never see it again.

Observing your gecko.
Now that is hard, they are pathologically shy, dark seeking, agile and strickly noctural. having gone to the trouble of feeding, housing and warming them it is only natural that you want to show them off and perhaps even watch them hunt. I have had to resort to setting up a security camera with infra red illuminators (they are not sensitive to IR light). If they are warm they are very active, hunting, contesting for territory or just hanging about on the glass. But all this in the dark. They are like fairies, if they see you watching , or sense your movement, the performance is over.

Gecko social behaviour.
They are notionally solitary animals. They do abide their own company and when they are cold they will huddle together in some favoured hiding place in bark or under a rock. In the breeding season they will contest for loosely held territory, the females for good spots to lay their clutch of two surprisingly large eggs. My enclosure contains a small succulent pot plant with sandy soil and the females really like this. I believe that it is safe to leave the hatchlings with the adults, I have seen no evidence of cannibalism. ^{yes, now I have seen cannibalism} The hatchlings are surprisingly large. It seems hard to accept that so much gecko can be contained in their little eggs. Geckoes caught wild can range in behaviour from rather passive to extremely aggressive. The aggressive ones will strike an "enemy" finger offered to them like a snake. They curl into a S curve and lunge forward with surprising force, perhaps enough force to frighten off a blackbird and the snake like behaviour could be an evolved defensive mimicry. Some geckos will become sufficiently finger tame that they may be removed from their enclosure and exhibited. Have your guests pull up their sleeves as a gecko that may panic will dash into the nearest dark space, which would be a guests sleeve! Most of the worlds geckos vocalise. Sometimes we think we hear a high pitched chirp, but these animals are regarded as silent. It is possible that their vocalization could be supersonic. One day I shall set up a microphone and oscilloscope to test this idea. It is rare to see overt aggression, recently however we observed two geckos in a life-n-death struggle, followed by the active tracking and persuit of one by its constestant. Was this mating behaviour ? It did not look very friendly. We still really havenet learned to distinguish male from female, except when gravid.
Canibalism.
After some 6 years of observation I can state that cannibalism does occur. It is extremely rare. Two hatchlings were partially eaten by a mature, large and aggressive female. She was ejected, (in disgrace!) back to the woodpile where she was first found.

finding geckos in Melbourne.
The southern marbled gecko is actually common, your house may have geckos living under eaves and biulding crevices. Look for the droppings, the dung looks like sparrow droppings, black,thinner than mouse droppings but capped in a white crystalline excressence in impossible situations, like upside down under an eave. You could have geckos for years but never see one due to their survival behaviour as described. The pressence of geckos could be indicated by an absence of brown house spiders in places and crevices where they might otherwise be found. If you have a pile of house bricks that face the afternoon sun, take the pile apart carefully, you might be rewarded. Our favourite gecko "Grump" appeared to have been trapped in the small concave cavity in a house brick that was resting against the flat surface of its neighbour. She had grown very large in this cavity and I dont believe would have been able to leave it. This possibly explains her bad temper! If you have an outdoor wood pile of parallel boards that gets afternoon sunlight, again look carefully, there may be a gecko in the space between planks. There will be an absence of small spiders, only some very large ones that the gecko cannot tackle. Late afternoon sun exposure seems to be the key for finding gecko habitats, and I would guess in Southern Victoria's "cold" climate, late afternoon sun exposure is mandatory.

Look behind tree bark, I have not actually found any on the eucalypt trees in my neighbourhood, the spiders to be found there suggest that no other life forms are possible and are welcomed only as dinner! The premier place where I can guarantee finding one is in front to trunk cavity of palm trees, in particular the large palm trees of the Kocos Palm variety that have a very large flat area of dead frond, thats enclosed at the bottom so it collects water, dirt and insect detritus and many spiders. Geckoes love this habitat. If you have one of these larger palm trees in your neighbourhood you will have geckos. In this habitat they are totally protected from birds. If you have this tree in your garden do not remove all the dead fronds, by all means trim off the dead frond but leave in place the bit that wraps around the trunk, this will attract, breed and maintain the gecko.

Melbourne reptile shops sell these animals for about $40 each. They are not very popular because of their pathological shyness and their propensity to escape. They will also sell you a good fully sealed enclosure. I have recently noted the local reptile shop selling the so called "Horned Gecko" which make better display animals. These are not frightened by light and will hang about on the glass of their enclosure.

More work colleagues are telling me that they find this gecko whilst doing building work that exposes their retreats. They appear to be fond of weather-board construction, which makes perfect sense. These anecdotes are pointing to the eastern suburbs.

finding a lost gecko
Sometime about half a year ago, Grump-the-gecko managed to escape. We dont quite know how, but Grump was a powerfull little animal and may have succeeded in lifting the lid on the enclosure. We could not find it in the house, that did not come a a surprise, because unlike a lost pin, a gecko does not WANT to be found. At least a pin, once lost in the haystack, will not actively seek out an even darker corner to hide in! A gecko hiding in the corner basically just looks like more corner ! I was demolishing part of an external wall, and had seperated a large sunward facing board from the house. There was Grump ! who had been living quite happily, it would seem, in this narrow crevice , eating house spiders. Grump was not happy to see me again but has rejoined her cousins in the enclosure. Grump confirmed one suspicion of mine. The only real food available here were small brown house spiders and juvenile white-tailed spiders of which we have more than our fair share. In this particular area there was a noticeable absence of smaller spiders, only fully grown mature specimens. The gecko had even left its droppings in a totally dark and invisible space. It was easy to loose site of the fact that Grump was a wild animal and quite capable of looking after herself, something one tends to forget after years of care. She is still just as bad tempered and still lunges at and bites your finger, sometimes emitting a little hiss. She still has her original tail, so outright aggression/bluff looks like a usefull behaviour for this little animal.

legalities
The Southern Marbled Gecko is currently not protected by law, no license is required to acquire and keep them.
The Museum of Victoria lists this animal as "common" especially in the Eastern side of Melbourne.

frequently asked questions

This paragraph was added to address the many frequently asked questions that I get at my email address , below. I am currently recieving about one enquiry a day from people that have encountered this little lizard for the first time in the greater Melbourne and now Geelong area. The range of this animal is expanding and this is being reflected in the increasing volume of email enquiries.

will you answere email questions?
Yes, the email address is valid, I will endevour to answere all questions. Never feel shy about asking.

I found this little lizard on the wall, what should I do with it ?
Unless you are serious about keeping it, and it is one that you can legally keep, return it outside where it belongs. It is perfectly capable of looking after itself. In keeping this little reptile you accept responsiblity for feeding it, which, believe me, is expensive.

Is this lizard safe to leave in the house?
Yes, you and your house are safe from this gecko. However, this little gecko is not safe from you or your house ! The gecko entered your house through a ventilator, external crack or under the door. Its instinct is to seek out crevices where its insect prey can be found. Most houses and kitchens simply do not have sufficient insects or freely accesible water around to keep the gecko alive. Unlike Asiatic and tropical geckos, it will not gather around light bulbs catching flies; it is too shy. Gently return it outside. Geckos are not venomous. If you cannot bear the thought of touching it, goad it into a dark cardboard box and put it outside.

Does it carry diseases ?
Reptiles are not generally known for harboring pathogenic organisms dangerous to humans. It is safe to touch and handle but the usual rule about handling animals applies, allways wash hands after handling. They will not foul your food, or enter a pantry except in the persuit of insect pests! Given that the main diet of tropical house geckos are flies, baby cockroaches and mosquitoes they have probably prevented more deaths from malaria, in the households that tolerate them, than any other artificial solution.

Can I keep it ?
Yes, The Southern Marbled Gecko is not protected, no DSE licence is required. Think carefully about the responsibility that comes with keeping an expensive to feed wild animal.

I want to let my captured gecko go, where is the best place ?
Palm tree if you have one, tree with loose sheetlike bark, woodpile, brickpile or "just outside in the garden". Anywhere that they can hide. Birds and cats find them attractive (for dinner!).

Best site that I have yet found for reference material related to all Australian Reptiles ,The Australian Museum, Sydney

http://www.amonline.net.au/herpetology/research/

The following is a literal extract from the excellent work of A E Greer.
Follow the link to the Australian Museum. The entire set of documents contains all you could possibly want to know about Australian Reptiles presented as formal academic papers.

The citation as requested by the author follows:

Greer, A.E. 2006. Encyclopedia of Australian Reptiles. Australian Museum Online
http://www.amonline.net.au/herpetology/research/encyclopedia.pdf Version date: 7 August 2006.

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Christinus marmoratus
Distribution. The species ranges along the southern parts of the mainland from northeastern
New South Wales to southwestern Western Australia. It occurs on a number of small off-
shore islands including in South Australia, Greenly I. (King and Rofe, 1976), Hopkins I.
(Hudson, 1981), Kangaroo Island (King and Rofe, 1976) and Pearson I. (King and Rofe,
1976) and in many islands in Western Australia, (Storr, 1987).
In the Western Australia, the species extends further north along the coast than it does inland
(Storr, 1987: fig. 3), presumably in response to the cooler temperatures due to the proximity
to the sea.
The species' distribution in New South Wales based on voucher specimens in the collections
                                                                          of the Australian Museum is shown
                                                                          in the accompanying map.
                                                                          Habitats. The species occurs in a
                                                                          variety of habitats including open
                                                                          shrubland (Kearney, 2002),
                                                                           sclerophyll forest (Daniels et al.,
                                                                          1986) and riverine woodland (King
                                                                          and Rofe, 1976).
                                                                            Daily activity. The species is
                                                                          nocturnal in its activity in the open.
                                                                            During the day it shelters under rocks
                                                                           on rock (Ehmann, 1976; King and
                                                                          Rofe, 1976; Kearney and Predavec,
                                                                          2000; Kearney, 2001, 2002), rock on
gravel or soil (R. Hughes, in Bustard, 1965c), or under the exfoliating bark of tree trunks
(Ehmann, 1976; King and Rofe, 1976; Doughty and Thompson, 1998; Thompson and
Russell, 1999). When it occurs in areas of both rocks and trees, it generally shelters under
rock by day and forages in trees by night (Kearney and Predavec, 2000; Kearney, 2002).
Density. In an Acacia shrubland in rocky country, the species may reach densities of 150 per
hectare (Kearney and Predavec, 2000; Kearney, 2002).
Aggregations. The species sometimes occurs in aggregations, which may number up to ten
individuals (Kearney et al., 2001). These seem to be more common in spring (Kearney,
2002).
Thermal relations. Although the species stays under cover during the day, it probably
thermo regulates by taking advantage of the thermal mosaic in its shelter (Kearney and
Predavec, 2000; Kearney, 2002).
The geckos also seem to go though seasonal shifts in their shelter sites, presumably as part of
their attempt to regulate their body temperatures (Kearney, 2002). In a population in central
Victoria, the geckos tended to shelter under rocks in spring but then move to crevices in
summer (Kearney and Predavec, 2000; Kearney, 2002). In this population, the lowest body
temperature at which an individual was observed foraging was 7.9º C and the highest body
temperature recorded was 34º C (Kearney and Predavec, 2000).
In the field in southwestern Australia, mean body temperature during the day was 19.6º C (n
= 5) and during the night 14.1º C (n = 7)(Froudist, 1970, as reported in Angilletta and
Werner, 1998).
In the laboratory, the geckos shelter between rock slabs, and if the upper slab is suitably
warm, they will raise their heads and backs to contact the slab and presumably gain heat
through conduction (Kearney, 2001). Prior to raising their backs against the overlying slab,
the geckos often contact the underside of the slab with their snouts as if testing the
temperature (Kearney, 2001).
In artificial thermal environments, the geckos have mean body temperatures that range 23.6 –
27.8º C (Licht, Dawson, Shoemaker and Main, 1966; Daniels, 1984; Kearney and Predavec,
2000; Kearney, 2001; Angilletta and Werner, 1998). The highest body temperature that the
gecko voluntarily tolerates is 31º C (Kearney and Predavec, 2000). The lowest body
temperature it can not survive is 43.5º C (Licht, Dawson and Shoemaker, 1966).
In a laboratory thermal gradient, there was no significant difference between the diurnal
(27.6º C) and nocturnal (27.8º C) preferred body temperatures, the overall mean being 27.7º
C (Angilletta and Werner, 1998).
Vocalisation. Although most other Australian gekkonine geckos vocalise, observers who are
familiar with the species note that it apparently does not vocalise (Annable, 1983).
Diet. In captivity, the geckos can be maintained on crickets (Kearney and Predavec, 2000),
fruit flies (Daniels, 1983; Daniels et al., 1986) and domestic flies (Bustard, 1965c).
When the geckos are maintained at 10º C with no food but unlimited water, they die after
losing about 22-23 percent of their total mass if they have tails (complete or regenerated) or
after losing about 17.5 percent if they lack tails. Under these same conditions, geckos with
tails live significantly longer than geckos without tails, about 112 days (n = 12) vs 49.2 days
(n = 10). This shows the importance of the energy, probably mostly as fat, stored in the tail
(Daniels, 1984).
In response to a standard “pull”, freshly-caught geckos lose their tails more quickly than
starved geckos in captivity (Daniels, 1984). Assuming that starvation is the critical
difference (and not some other condition of captivity, such as fear), it would appear that
geckos that are losing condition hang onto their remaining energy stores longer than do those
in better condition.
Fat storage. The percent of the dry body weight represented by fat increases in both the body
and the tail with snout-vent length, and the rate of increase is faster in the tail than in the
body (Daniels, 1984:fig. 3). At hatching, the young have fat in the body but none in the tail
(Daniels, 1984). Consequently, fat as a proportion dry tail mass is significantly less in
juveniles than in adults (Daniels et al., 1986).

Courtship and mating. Based on analysis of reproductive state of preserved specimens, it
appears as if there are two different mating seasons, depending on location. In at least one
River Murray population, mating probably occurs between late spring and early autumn
(November-April), and females store the sperm until they ovulate the following spring (King,
1977). However, in the eastern part of the disjunct distribution in western Australia, mating
probably occurs in spring, about the time of ovulation in females (How et al., 1987 as
reanalysed by Donnellan et al., 2000). These two populations also have different karyotypes.
The eastern population has a female sex chromosome, but the western population lacks such
a chromosome.
In sperm storing populations, the sperm pass the winter in longitudinal lamellae in the
posterior part of the oviduct (King, 1977).
Reproduction. In southwestern Western Australia, females are mature at a snout-vent length
of at least 45 mm (Bustard, 1965c).
Along the River Murray in South Australia, gravid females occur between early and late
spring (early October-mid-December) (King, 1977; Thompson and Russell, 1999) and have a
mean snout-vent length of 54.7 mm (n = 40) (Doughty and Thompson, 1998).
In South Australia, the species may lay as early as early spring (16 September).
In central Victoria, the species lays in spring (Kearney, 2002). At this time, as many as 90
percent of mature female are gravid (Kearney and Predavec, 2000).
Once the eggs are ovulated into the oviduct, it probably takes 2-3 days for the shell to be laid
down (King, 1977). In the laboratory at 23º C, the shelled eggs are held in the oviduct for
about 12 days (King, 1977).
Frequency of reproduction. It has been asserted by an experienced researcher on the species
that the it lays only one clutch per season (Daniels, 1983), however no further details are
available.
Clutch size. This is one of the few species of gecko that frequently lay either one or two eggs
in a clutch, instead of almost always laying either one or two (Bustard, 1965c; Doughty and
Thompson, 1998). Among 40 females from South Australia, 27.5 percent laid one egg and
72.5 percent laid two eggs (Doughty and Thompson, 1998; see also Thompson and Russell,
1999). One female laid two eggs and 26 days later laid a single egg (Doughty and Thompson,
1998). What determines the clutch size either within or among individuals is unclear.
Relative clutch mass. The relative clutch mass for eggs from clutches with one egg averages
0.185 and for eggs from clutches with two eggs averages 0.341 (Doughty and Thompson,
1998).
Communal nesting. The species lays communally, with as many as 30 found in a single nest
(Ehmann, 1976). The same nest is probably used over more than one season (Hudson, 1981).
Nest sites. The nests are on the ground (Hudson, 1981), often under rocks (Kearney, 2002).

Eggs. Measurements and masses of freshly laid eggs are summarised below.
                             Width (mm)               Mass (g)              Reference
   Length (mm)
                         Range      Mean N      Range      Mean    N
Range        Mean
N
11.0-13.7 -          -   9.0-10.0    -      -   -          -      -     King, 1977
-            -       -   -           -     -    0.50-0.77 0.63   74    Thompson and
                                                                        Russell, 1999
-            -       -   -           -     -    -          0.63   40    Doughty and
                                                                        Thompson, 1998
12.5-14.0    13.4    4   9.5-10.0    7.3    4   0.67-0.69 0.68   4     Bustard, 1965c
There is no significant difference in mean egg mass between eggs from clutches of one or
two (Doughty and Thompson, 1998).
There is a significant positive correlation between mean egg mass and female post-laying
mass, both within a clutch size of one or two and among all clutch sizes (Doughty and
Thompson, 1998). In other words, heavier females produce heavier eggs.
Freshly laid eggs contain embryos at Dufaure and Hubert (1961) stage 26/27-29 with most
being at stage 27 or 27/28 (Thompson and Russell, 1999).
The water content of the freshly laid egg (not including shell) has a mean of 77.9 percent (n =
10). This seems to be higher than the few species of lizards for which there are comparable
data (Thompson and Russell, 1999) but could be another distinctive feature of the hard-
shelled eggs of gekkonine geckos.
Relative clutch mass. The relative clutch mass for two females laying two eggs each ranged
0.31-0.34 (mean = 0.325) (Bustard, 1965c, 1967).
Incubation. Incubation periods are different temperatures are summarised below.
Incubation               Incubation Period (days)
                       Range               Mean       N             Reference
Temp (° C)
-                   207                  207       2 or 4? Waite, 1929
“room”              70-87                -         -       King, 1977
25                  79-84                81.4      18      Thompson and Russell, 1999
25                  85-92                88.3      3       Bustard, 1965c
Eggs collected from a communal nest in the wild hatched in six weeks (Ehmann, 1976),
although the incubation conditions were not specified.
During incubation, the eggs loose very little water as expressed by only a slight decrease in
mass (Thompson and Russell, 1999). This is contrast to most lizards eggs and probably
shows the degree to which the hard-shelled eggs of this and probably other gekkonine geckos
(e.g., Gehyra, Heteronotia and Lepidodactylus in Australia) can conserve water.

Development. During development, embryos put on mass exponentially, but the upturn in the
curve does not occur until about day 50 in a 79-84 incubation period, that is, not until about
59-63 percent of the total incubation period (Thompson and Russell, 1999; fig. 2).
During development, the water content of embryos falls exponentially but the downturn in
the curve starts at about day 60 (Thompson and Russell, 1999; fig. 3). At hatching, the water
content as a proportion of wet total mass of the young ranges 65.4-77.4 percent (mean = 70.6
percent, n = 14)( Thompson and Russell, 1999).
The metabolic rate of developing embryos is a very gentle sigmoid curve, the final rate being
about 9 µL/h (Thompson and Russell, 1999).
Hatchlings. Measurements for hatchlings are summarised below.
Snout-vent Length       Total Length            Mass (g)
       (mm)                  (mm)
Range Mean N           Range Mean N         Range      Mean   N           Reference
26       26.0    2     52-53     52.3 3 0.45-0.48       0.46   3     Bustard, 19675c
-        -       -       -       -       - 0.36-0.57    0.47   14    Thompson and
                                                                     Russell, 1999
There is a significant positive correlation between hatchling mass and egg mass (Doughty
and Thompson, 1998). In other words, larger eggs produce larger hatchlings.
Hatchlings have brightly coloured tails featuring orange-red markings (Bustard, 1965c). The
function of this bright tail colour is unknown (Bustard, 1965c).
Sex ratio. The number of mature males and females was not significantly different in a
population in central Victoria (74:63) or on Sandy Hook Island in Western Australia
(42:41)(Kearney et al., 2001).
Sexual dimorphism. There is significant sexual dimorphism in snout-vent length in two well-
studied populations at the opposite ends of the species’ range. On both Sandy Hook Island
off the south coast of Western Australia and in central Victoria, mean snout-vent length is
larger in females than males (Kearney et al., 2001).
Chromosomes. Large sections of the wide distribution of this gecko are characterised by
distinctive karyotypes. In the southeastern part of the country, the diploid chromosome
number is 36 with no sex chromosomes. However, along the River Murray there is a
population that has chromosome pair four heteromorphic in females; that is, females have a
sex chromosome. In the southwestern part of the country there are three different karyotypes.
Roughly from north to south and from larger to smaller overall areas, these are a diploid
chromosome number of 36 (similar to that in the east), 34 and 32, none with sex
chromosomes (King and Rofe, 1976; King, and King, 1977; Donnellan et al., 2000). The
diploid 36 with sex chromosomes appears to be ecologically distinct in only occurring in
riverine woodland and not occurring under rocks (King and Rofe, 1976).

Predators.

Defence. In captivity, when a gecko is approached by a small mammalian predator, it may
respond in one of several ways: remain motionless, vibrate the tail laterally against the
substrate, vocalise, defecate or run (Daniels et al., 1986).
The ability to drop the tail, or tail autotomy, is probably one of the most important responses
in escaping predators (Daniels et al., 1986). In this regard it is interesting to note that in
response to a standard “pull” at temperatures between 5 and 20 C, juveniles loose their tails
more quickly than do adults. This may be due to the lesser relative amount of fat in the tails
of younger animals than in older animals and hence the loss of resources can be more readily
endured. At temperatures between 25 and 35 C, there is no significant difference between the
two age groups (Daniels, 1984).
Locomotion. Geckos that have lost their tails run nearly twice as fast on average than geckos
with tails, either original or regenerated between which there was no significant difference
(Daniels, 1983). Mean running speed for adult geckos with tails (both original and
regenerated)(n = 39) was 0.93 m/s (3.35 km/h) and mean running speed for geckos with
recently autotomised tails (n = 20) was 1.75 m/s (6.3 km/h)(Daniels, 1983). The tail probably
plays no important role in locomotion. Indeed, it may simply add to the load from the point
of view of locomotion, as it comprises a mean 21.2 percent (regenerated) or 23.92 percent
(original) of total weight (Daniels, 1983).
Parasites. The species' recorded parasites include cestodes (tapeworms)(Angel and Mawson,
1968), nematodes (round worms) (Angel and Mawson, 1968; Mawson, 1971) and trematodes
(flukes)(Mawson, 1971).
Literature. Gray, 1845; Waite, 1929; Bustard, 1963 (as Phyllodactylus porphyreus); Bustard,
1965c; Licht, Dawson and Shoemaker, 1966; Licht, Dawson, Shoemaker and Main, 1966;
Bustard, 1967; Angel and Mawson, 1968; Mawson, 1971; Ehmann, 1976; King and Rofe,
1976; King, 1977; King and King, 1977; Daniels, 1981; Hudson, 1981; Daniels, 1983;
Daniels, 1984; Daniels, Flaherty and Simbotwe, 1986; How, Dell and Gordon, 1987;
Annable, 1995a; Angilletta and Werner, 1998; Doughty and Thompson, 1998; Thompson and
Russell, 1999; Donnellan, Aplin and Dempsey, 2000; Kearney and Predavec, 2000; Kearney,
2001; Kearney, Shine, Comber and Pearson, 2001; Kearney, 2002.

(apologies for mangling the format from the original pdf. The distribution map didnt make it but its shows the known distribution from SA, southern NSW through to central Victoria. It does not mention Melbourne, this could be news!) The range of this little animal is now increasing through out the Melbourne area. They were non existent when I was young and would have noticed them. Now forty years on they are becoming very common.

Everybody loves a blue-tongue !

Nanna K and "Fatso" the blotched blue tongue

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Tue May 26 14:07:35 EST 2009
added images, email sig
Thu Dec 10 17:58:19 EST 2009
added remarks about cannibalism and cricket care.
Mon Feb 22 18:03:31 EST 2010
added FAQ section


visible here is their wooden wedge habitat	just visible here is the homemade 10W heater in a die cast box


mucking out the enclosure	geckos can be found behind the dead fronds along the main trunk in parlour palms	mucking out time