Knobtailed gecko - Nephrurus levis
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Pilbara Pythons would like to thank our good friend and Gecko specialist John McGrath for writing up the following information exclusively for this site.
The Nephrurus levis Complex.
The Complex
The N. levis complex is generally considered to comprise 3 subspecies; N. levis levis, N. levis pilbariensis & N. levis occidentalis. Recognition of subspecies is easily confused, & this has not been aided by the fact that several on line reptile sites have published photos which are obviously incorrectly labeled or at the very least, atypical. Sometimes referred to as the Smooth Knob Tail (not to be confused with N. laevissimus) N. levis is more often called the Three Line Knob Tail.
All subspecies have very similar morphology & some characteristics ascribed to the different subspecies can be ambiguous or difficult to apply. It is important to note that markings, ground colour & shape & size of the tail can vary significantly within a subspecies. The following short descriptions are not intended as a scientific resource. They are provided as an introduction to the novice & are based on personal observation as well as published descriptions.
IDENTIFICATION
N. levis levis
The most widespread subspecies, ranging from the eastern interior of Western Australia through central Australia to western Queensland. Adult females are approximately 12cm. total length with males slightly smaller. Ground colour varies from charcoal to red to an olive yellow which is quite uncommon. Individuals may or may not have a prominent creamy stripe following the backbone on the dorsal surface, and distribution & frequency of small white tubercles varies. Specimens from Tanami region in particular display a number of thin white lateral stripes.
N. levis pilbariensis
Confined to the Pilbara region, a definitive characteristic of this subspecies appears to be the presence of large scattered granules on the throat. The tail is described as being larger & flatter than N. levis & overall size often noted as slightly larger.
I have a problem with the latter 2 criteria.. Tail size & shape is very variable; in addition, since the tail is used to store fat, relative condition of a particular specimen will help determine the size & shape of the tail.
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Knobtailed gecko - Nephrurus levis pilbarensis
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Knobtailed gecko - Nephrurus levis tanami desert
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Furthermore, SOME of the adult females I have seen are considerably larger than N. levis levis, whereas adult males tend to be similar size to N. levis or even slightly smaller.
Taking a simplified, macroscopic view, whilst ground colour varies similarly to N. levis levis, the Pilbara subspp. commonly has more prominent dark markings, perhaps best described as blackish lines or a network that is broken in many places. This patterning is absent in N. levis levis. I have also observed in a significant number of specimens that ground colour of the tail differs somewhat from that of the body.
N. levis occidentalis
Restricted to the arid & semi-arid west coast of Western Australia, this subspeciesis described as having a larger, wider & more depressed tail than other members of the complex.
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Again, this criteria is in practice very hard to judge. In appearance, occidentalis appears more uniform in colour than the other subspecies; there are less markings & the small white tubercles are less noticeable. The ground colour is often yellowish or relatively pale.
CAPTIVE MANAGEMENT
N. levis levis is well established in the hobby, whereas N. levis pilbariensis & N. levis occidentalis are not common & relatively new. I have not personally kept occidentalis, however captive management for levis & pilbariensis is identical & there is no reason to suspect that occidentalis should be different.
These are hardy animals that do well in captivity; they are relatively easy to keep & breed. The following notes are based on personal experience & that of acquaintances in the hobby.
Housing
Pairs or trios are adequately housed in a standard 2ft. aquarium. There is no requirement for a lid since the animals do not climb. Desert sand is my preferred substrate. A 2cm layer is mounded up to approximately 15cm at one end, where an upturned terracotta flowerpot saucer is used as a home site. This area is moistened by misting every couple of days so that the sand does not dry out. Substrate should be moist but not wet.
These are burrowing animals & will dig extensively in the mounded sand. A drinking bowl may be provided, however I have found that the animals prefer to lick droplets of water when the cage is misted.
My animals have good access to natural daylight but no additional lighting is provided.
Temperature/Heating
During summer months background temperature is held at approximately 26 degrees, 24 hours a day. In addition, a heat source is used to raise the temperature by about 2 degrees in the vicinity of the home site. I prefer to heat from the side of the enclosures (at or about the level of the sand) rather than from below, since this will result in the substrate drying out more quickly & rapid dessication of eggs.
Slightly higher temperatures should not be a problem; due to heating costs I tend to maintain my animals at minimum end of optimum range.
A cooling/resting period should be provided during winter months. I use a minimum of 3 months which is structured as follows:
Weeks 1-3; progressively lower temp.
Weeks 4-9; hold temp at daytime 24 degrees, nighttime 17 degrees
Weeks 10-12; progressively raise temp.
Feeding
My animals are fed exclusively on crickets. Roaches are also used extensively, however being faster than crickets they are more difficult for the animals to catch. This can be countered by maiming the roaches or by placing them in a refrigerator for a short period. Adult animals are fed 3-4 large crickets twice a week, with every second feed being dusted with Calcium & vitamin powder.
Since the tail is used for fat storage, it is a good indicator of an animal's condition. The tail will quickly reduce in size as an animal loses condition.
Sexual Dimorphism
Since males are considerably smaller than females, it is possible to guess with some accuracy the sex of clutch mates at an early age. Confirmation is made by examination of external genitalia at approximately 6 months of age. Females are quite flat around the cloaca, whereas males have a noticeable swelling.
In addition, mature males possess a small white “pimple” on each lateral surface close to the base of the tail. It is possible to view this from a dorsal aspect.
Breeding
I have successfully bred N. levis levis at approximately 7 months of age, although most individuals take a little longer. Mating will take place shortly after temperature is raised following winter cool. Gravid animals can be recognized from either the ventral or dorsal surface by the pale outlines of eggs in the abdomen.
Two eggs are laid (rarely one); these are usually laid close to the bottom of the cage in the moist sand & then covered over. It is important to remove the eggs quickly since they will rapidly dessicate (especially if laid near a heat source).
Under ideal conditions, females will lay every 17-21 days & can have up to 10 clutches per season. It is important to monitor females' condition carefully during the breeding season, & is generally agreed that the production of a large number of eggs may shorten life span.
N. levis levis will hatch at approximately 65 days if incubated at 28 degrees; N. levis pilbariensis frequently require slightly longer (commonly around 73 days).
Hatchlings
In my experience clutch mates are almost always one male & one female. Therefore it is important to keep clutches separate upon hatching since most people will prefer to obtain a pair. Hatchlings do not require any special treatment; they are kept in small containers for several months in order that they do not have trouble locating food items.
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