The Care and Husbandry of Diplodactylus Geckoes (Part 1)

By Dr Danny Brown BVSc(Hons) BSc(Hons) MACVSc(Avian Health)

Species Descriptions

The Diplodactylus genus is an endemic Australian group comprising two subgroups. Diplodactylus means literally double fingered referring to the paired apical subdigital lamella present in most (but not all) species within this group. Some confusion often exists in texts which refer to Subfamily Diplodactylinidae and Subfamily Gekkonidae. Subfamily Diplodactylinidae comprises all world wide species that lay soft parchment type eggs (whilst all Gekkonidae lay round hard shelled eggs). Most Australian species of gecko (including Diplodactylus species) fall into Subfamily Diplodactylinidae. The generally terrestrial forms are what will be covered in this article. The second group of mostly arboreal species are often separated into the genus Strophurus by some authors and most of these will be covered in another article.

Terrestrial Diplodactylus currently comprises 23-25 species (depending on your taxonomic preferences). This group comprises a broad range of gecko types ranging in size from the smallest D. occultus at 41 mm SVL to D. immaculatus at 85 mm SVL. A typical specimen of 50 mm SVL will weigh on average only 3-5 grams.

All species within this group are generally either robust bulky species with short limbs and tail or elongate species with longer limbs and tails. Most individuals of these species are shades of brown with degrees of spotting, striping and mottling which reflects their terrestrial habits and need for cryptic colouration. Even within a single species however, there is considerable colour variation depending on the origin of the animals geographically.

Despite considerable variation within each species, little effort has been made by taxonomists to split these regional variations into subspecies. Only D. granariensis (Wheat Belt Stone Gecko) has subspecies allocated . D. granariensis granariensis has a wide distribution from Hutt River, WA in the northern extremes of its range to Spencer Gulf, SA . Within this subspecies a northern colour pattern , a southern colour pattern and a West Coast colour pattern are recognised. Northern and southern colour patterns merge and mix in the Southern Wheatbelt area of W.A. D. granariensis rex is larger and more robust than the nominate, has a more prominent vertebral stripe and lacks a groove in its rostral scale. It is found in the arid southern interior of W.A.

Some species such as D.stenodactylus (Pale Snouted Gecko) has distinct geographical colour forms with significant geographical borders between them but these have not yet been classified as subspecies.

Hatchlings in this group are essentially similar to adults in colour pattern albeit somewhat brighter. Hatchling SVL’s are on average 25-30% of adult SVL.

Distribution and Habitat

This species group is spread throughout much of Australia but is restricted predominantly to arid and semi-arid areas. These species live amongst stones, organic debris, fallen timber, soil cracks and often utilise disused reptile or spider burrows. Some species are restricted in range by specific habitat requirements (e.g. D. galeatus (Helmeted Gecko) utilises primarily arid quartz outcrops ). These species forage by night in open ground and under foliage.

Dietary Requirements

For most species in this group (the exceptions being D. conspicillatus (Fat Tailed Gecko) and D. pulcher), feeding is a simple matter with both adults and juveniles accepting any small insect. The natural diet comprises small spiders, ants, cockroaches, crickets, termites and moths. In captivity they will accept crickets, cockroaches, termites, flies, maggots, moths and waxmoth larvae. For adults, these should be fed every 4-7 days in summer and every 7-10 days in winter (although they may not accept food for short periods during this time). Juveniles should be fed every 2-4 days and ideally this should be continued all year round. Termites are an ideal food for juveniles as they are easier for the young geckoes to catch although crickets are easier to supply. Ideal food item size is approximately 60% of head size. Food items should be lightly dusted with a suitable calcium and vitamin supplement every 2^nd or 3^rd feeding.

D. conspicillatus (Fat Tailed Gecko) and D. pulcher are specialist termite feeders in the wild. Attempts to convert these species onto other foods has been variable in its results. Some individuals will readily follow and strike small food items of similar size and colour to termites (small waxmoth larvae and pinhead crickets). Other will actively follow items but will fail to strike after sniffing the item. This suggests that scent may play a partial role in food selection. Initially scenting alternative items with crushed termites has resulted in better feeding responses. Weaning off scented food can then be slowly implemented. Results can certainly be frustrating at times, but captive bred individuals are faster to learn than wild caught specimens. If available, termites are certainly far superior and greedily eaten. Due to the poor storage qualities of termites (once removed from the nest) they will desiccate within 24 hours once in the lizards enclosure and should therefore be fed at least twice weekly .

Sexing

Adults may be sexed by the presence of enlarged hemipenal bulges in males. Females of this group will show some enlargement in the “hemipenal” area but these are usually a smooth enlargement without any central depression. Males of this group possess unique (for each species) “cloacal spurs” consisting of an arrangement of spines 2-3 times larger than the surrounding scales. Depending on the species, the spine cluster may involve 2-7 enlarged scales. They are positioned near the top of the hemipenal bulge near where it contacts the hind leg. If these are visible in female animals they are positioned similarly but are rarely more than 50% larger than the adjacent body scales. Some males may undergo an apparent seasonal reduction in hemipenal bulge size. Although the hemipenal bulge bulk may be reduced , the central depression and tubercles remain as indicators. In D. stenodactylus (Pale Snouted Gecko), a consistent resting colour dimorphism is apparent with females developing a paler body colour than males. This is less prominent in active , feeding individuals. I am uncertain if this is purely a captive phenomenon as I cannot recall having noticed it in wild caught active animals nor have I observed wild resting individuals. D.steindachneri (Box Patterned Gecko) also appears to show this dimorphism as hatchlings but this is not consistent with differences in gender as adults (I believe that in this species it is a feature of dominance with the darker animals being dominant). Juveniles of this group can generally be sexed once they have attained 60-70% of adult SVL (attainable with good feeding in 6-12 months).

Housing

The terrestrial nature of these species makes them relatively easy to cater for. Although most are entirely terrestrial, they are capable of climbing smooth surfaces so it is recommended that all enclosures should have lids. Enclosures should provide at least 20 cm x 20 cm per pair of floor area. Excessively large enclosures are not necessary as these species utilise only a small area of the floor space provided. This species may be housed as singles, pairs or males with multiple females (up to 3). Enclosures need only be escape proof and of suitable dimension. Plastic tubs or fish tanks with lids are easy suitable options.

No supplementary lighting is necessary. If heating is to be provided then a heat mat or self regulating heat tape is most suitable and should provide a portion of the floor with a summer temperature maximum of 28- 30 ° C. During cooling, temperatures may be allowed to drop to 15-20 ° C.

The preferred substrate should reflect the natural substrate of the species. For most species a sandy loam is suitable with additional substrate components such as bark pieces, upturned terra cotta saucers and small rock piles appreciated. A substrate depth of 1-5 cm is suitable. The substrate should be kept lightly moistened at one end or a moist hide provided (I prefer the latter). Some keepers regularly “mist” their terrestrial geckos . This is not necessary and in my experience leads to a higher incidence of parasitic and bacterial disease issues by providing a means of pathogen transfer (via microfilms of water) and better pathogen survival. I do not personally recommend it. Artificial spider burrows may be created by making a suitable sized depression in the sand with your finger or utilising small pieces of plastic pipe (such as electrical conduit) cut in half lengthwise. These are pushed into the sand with the pipe forming the roof of the burrow.

Reproductive Behaviour

These species generally breed during the early spring to early summer period (Sep-Feb). Northern species may breed more often a little later in the season (Nov - Mar). Courtship displays are rarely described for these species presumably due to their secretive nature. A male D. vittatus (Eastern Stone Gecko) has been observed biting at the neck of a female in the chase period immediately preceding mating. These species will grow rapidly and with good feeding will reach adult size at 12-18 months of age. Breeding may occur in individuals of at least 70-80% of adult SVL.

Pairs (or up to 3 females) of these species may be kept together throughout the year. Separation of sexes may be utilised and may allow for both males and females to rest prior to breeding, but it does not necessarily improve breeding outcomes. Cooling due to naturally lower ambient winter temperatures is all that is required and breeding may occur even if this is not intentionally provided. Regardless of the cooling technique used (or not used) most individuals will still breed at the same time each year. First eggs may be expected as early as 4-8 weeks after the natural ambient temperature starts to rise (usually above 25 ° C). Females will develop obvious increases in girth during early ovulation and eggs will later be visible through the abdominal wall in some species. The eggs usually number 2 per clutch but sometimes only 1 may be laid. Females of this group will often lay in shallow scrapes dug in moist sand (covered after laying), on the sand surface under a hide structure or, as is frustratingly more typical in captivity, in the open. If laid in the open, the eggs may dehydrate quickly especially if laid on dry sand. If the eggs are markedly sunken but less than 24 hours old they may recover if placed in a vermiculite tub with a piece of wet toilet tissue over them. It may take 3-5 days for these eggs to rehydrate if the embryo is still viable. Even if ideal sites are supplied, many females will repeatedly lay in unsuitable sites. My best results have been using small take away containers (with lids) placed upside down (the lid forms the floor). A 1 cm hole is cut on the upper edge and the container is filled 2/3 full with moist peat moss. The container is buried slightly so that the entrance hole is level with the soil surface. This method has been most successful with D. steindachneri (Box Patterned Gecko), D. tesselatus (Tesselated Gecko) , D. conspicillatus (Fat Tailed gecko) and D.vittatus (Eastern Stone Gecko).

Eggs should be incubated in vermiculite:water or perlite:water mixed at a 1:1 ratio by weight (or 1:10 by volume). A temperature of 27-30 ° C is preferred. Incubation at room temperature can be successful but it will increase incubation considerably and may leave the eggs more susceptible to fungal attack. The eggs of these species will expand considerably during incubation (as much as 50% increase in width and 30-40% increase in length). The eggs may develop an almost transparent shell when at peak pre-hatch expansion. Eggs usually “sweat” approximately 24 hours before hatching.

Some species will produce multiple clutches (up to 5) within a single season at intervals of 2.5 - 6 weeks apart. Prolific females should be separated from the males after 3-4 months of breeding to allow total rest. Apparent spermatozoa storage may still results in fertile clutches being laid by separated females. Excessive breeding from a single female may contribute to increased health problems in that individual.

Hatchlings are usually removed from the hatching container after 24 hours and can be placed in a container with similar substrate as the adults. Hatchlings of these species appear more settled with this substrate than when on unnatural substrates such as paper towel.

Breeding data from selected species is presented below.

SPECIES	BREEDING SEASON	INCUBATION PERIOD (at average incubation temperature)	MINIMUM INTERCLUTCH INTERVAL	EGG SIZE (Average Width x Length in mm)	SVL/TL (Average in mm)
D. conspicillatus	0ct-Mar	59-65 d	25 days	9.25 x 15.5	27/35
D. galeatus	Sep-Mar	46-55 d	18-21 days	8.5 x 16.5	---
D. granariensis	Sep-Jan	---	---	8 x 16	---
D. vittatus	Oct-Jan	---	---	8 x 15	30/45
D. tesselatus	Sep-Jan	---	---	6.5 x 14.5	---
D. stenodactylus	Oct-Jan	---	---	7 x 13	---
D. occultus	Dec-Feb	67-69 d	42 days	---	---
D. pulcher	Sep-Dec	39 d	---	8 x 16	- / 28
D. steindachneri	Sep-Feb	56-75 d	---	8 x 14	25/41

Status in Captivity

Many terrestrial Diplodactylus geckoes are held in relatively low numbers at present. This is predominantly due to difficult availability of initial captive bred stock and in many is due to their lack of size and bright colouration. These species make ideal beginners geckoes due to their relatively non demanding requirements. These species generally live for 5-8 years in captivity with an average productive period of 3-4 seasons being common.