The Care and Breeding of the Smooth Knob-tail Gecko (Nephrurus levis levis)
by Justin Julander

    Knob-tail geckos are some of the most fascinating lizards in the world.  Their large eyes, big heads, and small tails make for an odd combination resulting in a comical appearance.  They can be hardy and characterable captives if their needs are properly met.  As they are nocturnal and fairly secretive, they may be come easily stressed from too much handling and are not a suitable pet gecko, but are fun to watch and keep.  There are few caresheets on the web, and so hopefully this page can be a help to anyone who wants to keep these awesome geckos.  I have been keeping and breeding these awesome lizards for a year and a half, so I am by no means an expert, but with the help of some great friends (thanks Casey and Jim!) I have been fairly successful in keeping these geckos and am thoroughly addicted to these little gems.  They aren't too hard to keep as long as you recognize the important elements of keeping them happy.

Important Natural History
    Smooth knobs live in sandy areas and spend much of their lives in burrows.  They will make use of burrows made by insects or small mammals.  They are also great excavators and can dig an appropriate burrow quickly.  Moisture is retained by spending the hot hours of the day inside their burrows.  This is important to keep in mind when designing an appropriate cage for your geckos.  They are also nocturnal in habit and will forage at night for insects and other geckos.  They are ravenous preditors and track and attack prey with vigor.  They may also wave their knob in anticipation of a meal.  Little is known about their natural history and much of what we know about these lizards is from their behavior in captivity.

Caging
    Knob-tails can be kept in many different styles of cages, as long as specific needs are met. These needs are appropriate thermal gradient, proper moisture retention, and recognizable substrate.  Provide a thermal gradient from mid 70's on the cool end to high 80's on the warm end, which is easily accomplished with apporpriately placed heat tape or a heating pad.  A digital thermometer or infrared temp gun can be used to monitor temperature to make sure that it is not too hot for the geckos when setting up the enclosure.  I place a heating pad or strip of heat tape on the dry end of the cage and the cool end is also the moist end.  This prevents the moist side from drying out too quickly.  A thermal gradient functions in giving the geckos usable temperatures for jobs they need to do.  I have observed my gravid females as they spend time on the hot end while their eggs are developing.  In nature they will emerge from their burrows at night and will warm themselves on the sand that has been heated during the day, so this form of heat will need to be duplicated in captivity.  If they have proper heat then they can attain natural life events.  It is imperative when keeping reptiles to provide a proper thermal gradient to suit their needs for different natural tasks the animals must perform.  Failing to do this or providing an overall ambient temp is just trying to tell your animals what to use without taking into consideration that they need many different temps at different times to perform different biological processes.
    The second important need to be met is appropriate humidty.  This is fairly easy to provide by moistening slightly the sand at one end of the cage.  Fine sand is used with great results.  I would also reccommend the use of natural sand as opposed to processed sand made from crushed rock.  Natural sand is smooth and free of jagged edges, where processed sand is like walking on glass shards.  I am luck to live in Utah and have some access to the nice red sand of southern Utah to use in the gecko cages.  The sand on the moist end must be moist enough that it will clump when squeezed in the hand and which will hold a burrow.  You may also provide an inverted potting dish with a hole cut in the side or rocks SECURELY stacked over the moist area.  If the sand is deep enough, the geckos will make their own burrows.  The entrance of the burrows or the opening provided in the inverted container or terra cotta plant drainers will be plugged with sand to retain the moisture in the burrow.  If knob-tails aren't allowed to burrow and close themselves in in this manner, they will soon dehydrate with unfortunate results.
    As mentioned above these geckos need a natural recognizable substrate.  Natural fine sand works wonderfully.  Don't keep these geckos on something they don't recognize.  If kept on newspaper, leaf litter, or other substrate, they will not know what to do with it.  It would be like us living in our swimming pools; we could live there, but it wouldn't be that great.  I like to provide my females with an extra deep layer of substrate (4-6 inches) so they can prepare for nesting.  I have used sand from nature with no problems.  Once these simple needs are met and maintained, they are easy to keep.

Feeding
    Knob-tails in captivity will eat a variety of insects including crickets, mealworms, superworms, locusts, cockroaches and other appropraitely sized bugs.  I dust the food items with an appropriate calcium or multivitamin powder.  They can eat fairly large meals when compared with other geckos of similar size, but care must be taken not to feed them too large of food items.  They hunt at night and emerge from their burrows early in the evening, so they should be fed at that time.  Don't throw insects in the cage during the day or during the day when they are sleeping or they will lose their dusting and can cause other problems.  Crickets will lay eggs in the moist end sand which will hatch in the warmth and you'll have baby crickets everywhere.  The baby crickets will annoy and stress the geckos out alot, so it is a good practice to pinch the ovipositors of the female crickets to make sure no eggs are laid before feeding.  If you notice baby crickets in the cage, replace the substrate immediately to remove all the baby crickets.  Mist the cage once every couple of days in the summer warm months and less frequently during the winter cool.  If the geckos are out, mist them as well and so they can drink, licking the droplets off their face.

Breeding
    These geckos are quite prolific and give the chance will even lay themselves to death.  This must be kept in mind when preparing to breed.  Breeding and egg production tapers off and stops as the temperatures are reduced and as cage conditions become drier.  Knob-tails, like many geckos will produce clutches of two eggs and can multiclutch, laying many clutches a season.  Six clutches are about as many as you want to get from any one female, and that only if they are healthy.  If they are cooled in the winter months and returned to warmer conditions in the spring it is hard to stop these geckos from breeding. When introducing pairs, I have noticed important signals which indicated weather the female is receptive or not.  If a male and female are placed together and the female begins to raise her tail, wave the knobbed end around, and thrust her cloaca in the face of the male, then she is NOT ready.  Non-receptive females will also vocalize and avoid males when not receptive.  I have noticed that when a female increases food intake that she may be putting on weight for egg production and may be more receptive to a male.  Receptive females are very easy to discern from non-receptive females.  They will lie still as the male approaches with their tail down and quiet and submissive in behavior.  A male will generally immediately show interest and will begin by grasping the female by the nape the tail and eventially moving up to the nape of the neck.  The female will sometimes move her tail over the tail of the male.  He will begin breeding the female and breeding will last several minutes.  The geckos are in a semi-trance state and are not easily disturbed.  I once had a female that was not in proper breeding condition that I placed in a males cage for a couple minutes for a cage cleaning.  I came back to remove the female, but the male was firmly attached and wouldn't let go for the world.  I even picked the pair up and he still refused to let go.  They sure are exhibitionists.
    I keep pairs together until the female is noticably gravid, at which time I remove the male to another cage.  The female will begin to dig and will really rearrange the sand.  Many times you will know when the female has laid by the amount of sand that has been kicked around the cage.  If the substrate is not deep enough or the female does not find a spot to her liking, she may retain the eggs longer and this may lead to problems.  Make sure that you have sufficiently deep (around 3-6 inches), slightly moistened, sandy substrate.  My females generally dig down to the bottom of the container and lay the eggs on the surface of the rubbermaid container.  They will sometimes leave air around the eggs if the substrate is too moist.  They do a good job of placing the eggs in the best environment available.  Carefully dig up the eggs and incubate them around 82-85 degrees.  Incubate on slightly moistened vermiculite.  There should be a bit of condensation on the sides of the incubation chamber.  Don't overwater, as less moisture is less harmfull than too much.  Monitor the eggs occasionally to make sure they appear healthy and that they have not died during incubation.  Healthy eggs will generally not mold, and I have even had moldy eggs hatch into healthy babies.  They will take around 60 to 70 days to hatch.  The babies are kept individually as the adults and are fed on small insects that are dusted.  This is a rewarding and fascinating species to keep.  Have fun, and get addicted!