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Pachydactylus scutatus HEWITT 1927

 

Introduction
 
Pachydactylus scutatus is part of the north-western group of the genus Pachydactylus. The group includes nine species, namely P. scutatus, P. parascutatus, P. sansteynae, P. oreophilus, P. scherzi, P. punctatus, P. gaiasensis, P. bicolor and P. caraculicus (BAUER & LAMB 2005). The nearest relative of  P. scutatus is P. parascutatus. Both All these species show  very rough and keeled scales. Other, sympatric in the same area living, Pachydactylus species show rather  smooth scales and, more importantly, don’t have the ability to produce sounds as good as P. scutatus. 

 

male Pachydactylus scutatus
Adult male of Pachydactylus scutatus. © M. Barts
 
During two journeys to the north of Namibia, the authors found, inter-alia, Pachydactylus scutatus. On the first trip, the species was regularely found in the area  surrounding Twyfelfontein (Damaraland District) in north-central Namibia. Intensive searchs took place during daytime in a variety of biotopes: a modified habitat on a camping site, a parched river and smaller rock crevices. The same places where observed at night as well.  The  localities identify P. scutatus as an all-rounder. The geckos were found under small rocks, shrubbery, bigger limestones, bark, in knotholes as well as while walking vertical granite surfaces at an height of up to 10m. 

female Pachydactylus scutatus
Gravid female of Pachydactylus scutatus. © M. Barts
 
During our second journey, we found the gecko in similar localities in an area north of Sesfontein. Surprisingley it lived here together with Chondrodactylus fitzsimonsi and Pachydactylus bicolor. For the first time, we heared a male P. scutatus calling from a knothole near Opuwo. The call of this gecko is distinctive and still clearly noticeable from a 5 meters distance.
 
Distribution
 
Pachydactylus scutatus is endemic to north-western Namibia. The terra typica is Kowares near the Ethosa-plain (Hewitt 1927). The most southern locality the ostrich cave in the Jochmannswall at the northern Brandberg (van der Elzen 1983). In the North, the species is known to occur up to the Kunene-River, while the most eastern locality is the beginning of the Ethosa salt plain. To the west the species only occurs in the SkeletonCoast national park. During the research on this article, the distribution of this species could be extended to south-west Angola.

Habitat of Pachydactylus scutatus. Twyvelfontain, Namibia. © M. Barts
 
Sounds
 
The ability to generate sounds is known for many gecko species and some of them developed their sounds to a high level. (e.g. Ptenopus sp., Gekko sp.). In southern Africa, the geckos of the genus Ptenopus are likely to be the most talented ones in terms of generating sounds. In northern Namibia, virtually above Ptenopus sp. heads, lives a group of thick-toed geckos, which weren’t yet famous for the ability to generate sounds. Indeed, both authors know only a few published information about the sounds of Pachydactylus species (Gramentz & Barts 2004, Barts 2006).
 
In captivity, male P. scutatus are able to generate sounds in an interval of 4-5 seconds over a period of 2 to 3 hours. Sometimes the male might even start calling during daytime, but usually its concert starts one hour before the light is turned off. A call usually consists of 5-10 cawing, sounds, occasionally followed by 1-3 sharp chirr. After a short break of 4-12 seconds these sounds are repeated. These sequences can be repeated in a surprisingly fast way up to 3 hours. The not always present chirrs seam to correlate with situations of external appeals (e.g. high temperatures, hunting, presence of females). The calling period may carry on for weeks or even months.


Young male of Pachydactylus scutatus. © M. Barts

 

The sounds were only observed with mature males. Females not willing to mate only produce a release sound which sounds like a squeak with raising intensity. The calling gecko at Opuwo produced a call, which was equal to the one of another male of the population near Twyfelfontein. The latter sat on a very big tree , which the authors used as a shadow provider. It started shortly after dusk and continued calling until we finally found  and disturbed it.
 
At a place in Ugab river, the call of a P. scutatus was observed. Bauer recorded P. scutatus in an area, which is about 30km north from this place near Gaias. Therefore it is likely, that the Ugab is one of the southernmost localities. 
 
Captivity
 
Frankly speaking, Pachydactylus scutatus is easy to keep. Over three years different keeping models were tested, whereas pairs where faced totally different conditions. Humidity proved to be unimportant. High temperatures where tested over a period of one year and lead to an enhanced reproduction rate with two females. Tests regarding social behaviour resultet in the same reproduction rate no matter whether the animals were hosued together as pairs or larger groups. Special attention was paid to the tolerance regarding temperature. It turned out, that P. scutatus tolerates temperatures of more than 40°C, which would be certain death for many other Pachydactylus species from hot areas of southern Africa.
 
A tank of 20 x 20 x 30 cm (l x d x h) is adequate for housing a pair or a small group. Tanks of bigger sizes were tested, but didn’t enhance anything. In fact it turned out, that keeping and breeding of P. scutatus is easier, when it’s housed closer to eachother and to its food. However, itt needs to be taken into account that housing them in such small tanks probably causes more stress when kept in groups. Fine sand is used as substrate and is the preferred medium to lay eggs. As mentioned above, the geckos are real all-rounders, hence the hiding places can consist of almost anything. Cork, plates, plastic boxes and even concrete will be accepted. During breeding season, the animals are fed with 12-15 crickets (or other usual invertebrates) 2-3 times a week. During cooling they only get fed 1-2 times a week. 
 
Breeding
Geckos which are expected to reproduce, should be cooled down. Therefore lighting is slowly reduced from 13 to 10 hours. In parallel, temperatures are reduced to 21°C during daytime and 10-15°C at night. After 6-12 weeks, temperatures are slowly increased and lighting extended to 13 hours. The breeding season starts usually 4-6 weeks after this cool period and the males will start calling for females every evening. A female which is willing to mate will approach the male with a horizontal waving tail. The mating is gecko-typical. Corpulation lasts about 30 minutes. 

 


Copula of Pachydactylus scutatus in the terrarium. © M. Barts
 
Females will lay two oval eggs every 14-32 days, which correlates with the amount of food and temperatures . They measure 8.9 – 11.41 x 6.0-8.05mm (average of 10.145 x 7.492 mm, n=39) and are always burrowed in loose sand, mostly near vertical stone-plates. Recordings for twelve adult females over a period of three years showed a productivity of 5-13 clutches with 2 eggs per year and female.

Clutches of Pachydactylus scutatus. © M. Barts
 
Two females were kept at temperatures of 33-40°C during daytime and 23-26°C at night for a period of 28 months. They produced clutches regularly and constantly over a period of two years without showing any health problems. Both, after 40 months of captivity, are still alive and producing eggs. The fact that some of the eggs aren’t fertilised may relate to the high age of the male housed together with them.
 
Eggs are incubated at temperatures of 26-32°C and it takes 64-104 days (average of 75.84 days, n=19) for them to hatch. The eggs can be put into an incubator, but many babys hatched in the tanks of the adults. Hence, as with most Pachydactylus species, they recognise their own hatchlings due to their special colour and pattern. It’s almost certain, that this dichromatism plays a major role in survival and evolution of all the species in the Pachydactylus genus. In the wildlife, juveniles of many species would face a fast and certain death, if they weren’t tolerated in the adult’s hiding places. It’s possible, that the characteristic color of the hatchlings doesn’t cause any aggression. 

Captive born hatchling of Pachydactylus scutatus. © M. Barts
 
Hatchlings measure 17.57-19.9mm SVL(average of 18.414mm, n=9) and a tail length of 14.86-19.1mm (average of 16.951mm, n=8). The pattern of a feshly hatched P. scutatus shows an intensive gold-orange Body with an even more shiny tail. The intensity of the pattern and color is dependent on the temperature. The head is dark-brown with a white band at the neck.

Pachydactylus scutatus
Captive born hatchling of Pachydactylus scutatus. © M. Barts

 

 

Originalbeschreibung / Original description  

HEWITT, J. (1927): Further descriptions of reptiles and batrachians from South Africa. — Rec. Albany Mus., 3: 395, Pl. XXIII, fig. 2 — Terra typica: Kowaris, Namibia

 

Type, a single specimen in the collection of the South African Museum (No. 17471) collected by Mr. R. F. Lawrence at Kowaris, S.W.A. The species is related to montanus Meth. and Hwtt.,* from the KarasbergMountains (see PI. XXIII, fig. 3), but is easily distinguishable through the scaling of the dorsal surface, the large scales being contiguous in scutatus but well separated by granules in montanus.

Head rather large but flattened, snout long and pointed, about 1 3/5 times as long as the breadth of the eye which is fairly large: ear opening elliptic, oblique or nearly horizontal: rostral rectangular, about twice as broad as deep, just entering the nostril on each side: nasorostrala in long contact, two other nasals, first labial and rostral all bordering on the nostril: symphisial shield elongate, more than twice as long as broad, narrowing a little posteriorly where however it is almost as broad as the first labial: nine upper labials, seven lower ones: scales on snout flattened and more or less subequal, larger than any on the occiput: the latter scales include quite small sub-granular ones and others much larger which are somewhat keeled, elevated and almost subconical: on the temporal region slightly larger keeled scales occur and over the neck enlarged keeled scales predominate, the intervening small scales being few and scarcely noticeable: over the greater portion of the back and flanks, these imbricating enlarged and strongly keeled scales occur exclusively, the largest of them being situated dorso-laterally in the lumbar region: the much smaller smooth scales are restricted to a narrow mesial strip in the lumbar region: enlarged keeled scales also occur over the upper surfaces of thigh and leg, but on the forelimb the keeled scales of the anterior surfaces and smaller belly scales all small, smooth and imbricate, those over the throat and chin region much smaller still.

Tail lacking in the specimen, but in juvenile specimens it is cylindric and conspicuously-ringed above, each annulus having two or three row of small smooth scales, followed by a single row of four to eight much enlarged strongly keeled scales: ventrally, howered, there is no trace of annulation, the scales being smooth: reproduced portions also are not annulate, but the dorsal scales thereon are faintly keeled. 0n each side of the vent basally a pair of enlarged smooth scales. Expanded portions of digits with 6 lamellae interiorly, the terminal one being divided: in addition, the scales of the median row of each digit interiorly are all transversely elongated, the middle toe having nine such enlarged scales, and the middle six.

Head with a conspicuous colour pattern as follows—on each side a black stripe beginning in the loreal region, continued behind the eye, above the ear opening to the occiput where it curves inwards to meet its neighbour: behind the eye, this black stripe constitutes the upper border of a white strips which again is more or less distinctly bordered below with black: the main black stripe also is bordered above by a short white one just behind the eye and another along the ill-defined rostral canthus. Upper surface of body and of head with indistinct and irregular dark spots and blotches.

Length from snout to vent 42 mm., greatest breadth of head 9 mm.

Young specimens have the conspicuous head marking well developed but no black spots on the dorsal surface.