Karsten Grießhammer 2021: A small blog-article about the history of the Seidel albinos and the keeping and breeding of Underwoodisaurus husbandi.
The Australian thick-tailed gecko is a very attractive lizard that is also very easy to keep and breed in terrariums or rack systems. The most commonly kept species are the Underwoodisaurus milii, which look cute with their large beady eyes. Therefore, they are very popular with reptile keepers worldwide.
This article is about the much more rarely kept variety Underwoodisaurus husbandi and the albinos that have only recently become available. It is addressed more to experienced keepers and general husbandry details are therefore omitted as it is more about the specific aspects of keeping U. husbandi.
This article is dedicated to Uwe Seidel, who made this beautiful colour form available.
If you are interested in getting animals of this colour form, you can contact me here: firstname.lastname@example.org
History of the morph
In the late 1990s, reptile breeder Uwe Seidel was given a pair of geckos by a friend - they were Underwoodisaurus husbandi. Not only was Uwe lucky enough to breed the geckos, but he had a particularly bright young one among them: The first known Underwoodisaurus albino.
In the following years, Uwe returned a few offspring to his friend, the rest he kept and bred on a small scale without giving away any animals. In the 2000s, Uwe decided to concentrate on breeding other species. So in 2010 he took his remaining animals to the reptile fair in Hamm. Jürgen Eckert and I went to the same show with the aim of finding unusual U. milii. When we arrived at Uwe's table, we were mindblown when we saw his great animals. Eventually we made the agreement that Jürgen and I would continue to work on this breeding project. It took us a few years to identify the optimal husbandry and breeding conditions and to build up a safe breeding stock.
Around 2015 Jürgen Eckert handed over his breeding share to Christian Horak, who from then on continued breeding the species with me. Christian even travelled to the habitat to study the natural conditions of the animals in order to validate and further optimise our husbandry experiences.
We also invested some time to verify that the colour form had no negative influence on the health of the animals. We also found the solutions to initial challenges with breeding the animals, which are described later in this article.
By the end of 2018, we were finally sure we had enough animals and knew enough about the ideal breeding conditions to release animals to few other experienced breeders who are now helping to establish the species in the hobby. Thus Christian and I were able to end our cooperation and are now breeding independently with U. husbandi.
This little description may help you to understand why it takes some time to establish a new species or colour form.
The other parts of this small article will provide more information about my experiences in keeping and breeding this beautiful variety. The Underwoodisaurus husbandi are very well suited for keeping in a terrarium and the exclusive colour form can awaken further interest to work with this beautiful species.
About the colour form
When you hear the term albino, you might immediately think of very light-coloured animals with red eyes. However, there are numerous other types of albino, and especially in reptiles one often finds so-called caramel albinos. These are usually "thyrosinase positive"/T+ forms of albinism and are manifested by the inability to complete the synthesis of melanin, but may produce other melanin-related pigments, e.g. various shades of brown-grey. While in hypos the body colours are lightened, in T+ albinos the colours are changed - dark colours then become more yellow and red, occasionally there are also brown tones. In geckos, such forms (also without red eyes) are found, for example, in amelanistic fat tails or in the albinos of Paroedura picta. As these geckos are nocturnal, this change in pigmentation does not seem to have a negative effect on the well-being or health of the geckos. In all species this colour form is inherited in a dominant-recessive manner. Unfortunately, we had problems to get guaranteed non-related animals to our line, which made test matings difficult, but the current state of knowledge indicates that the Seidel albinos also have a dominant-recessive inheritance.
In the many years we have been breeding with this colour form, we have not noticed any negative health influence. The behaviour, the age reached, the fertility and other factors were the same in our animals as in the wild type. The offspring have a wide range of variation - while some are more orange-brown, others are more reddish or yellowish. Some also have areas of translucent pigmentation. This leaves a lot of room for the breeders' creativity to establish their own lines.
The Seidel albinos can reach up to 35 grams and are thus at least as large as U. milii.
How to keep them
When you think of the habitat of Australian geckos, you probably have very dry sand dunes in mind. However, at least for the Underwoodisaurus species, this is not true. They tend to live in regions with very low vegetation such as grasses and small bushes. Here they always find moist retreats where they spend a lot of time. This can be simulated very well with a wet box, which can be filled with coconut peat, similar to the way leopard geckos are kept. Many different types of substrate can be used in the terrarium or rack system - soil, low-dust sand or even sand-peat mixtures have proven successful.
A very important point in keeping them is the temperature - U. husbandi prefer cooler temperatures. This makes keeping them very easy, as you can keep them more or less at room temperature. I keep my animals in a basement room with a window that is tilted all year round. Only in a small corner of the terrarium do I provide a hotspot with about 31°C, so the rest of the temperatures largely correspond to the room temperature and thus fluctuate from 15-28°C in the course of the year. U. husbandi do not tolerate permanently very high temperatures well. Some breeders have therefore even started to keep them in screen terrariums.
But there is no need to make it too complicated. The basic rule is: they tolerate a wide range of temperatures, but prefer the cooler ones.
U. husbandi that are under temperature-stress may continue to eat, but often stop producing eggs and the tail loses tension and becomes wizened. At this point at the latest, you should take countermeasures and keep the geckos cooler.
Underwoodisaurus milii is known to be found even in the wild in small groups in their hiding places. For U. husbandi I know of no reports on this but they too can be kept with several females or even with one male and several females. Until they have been kept with females for the first time, even males will get along with each other - but if they are sexually active, the males will bite each other aggressively. I can say, however, that I have had the best breeding results with housing them individually.
They are not very demanding when it comes to food and eat almost all insects that fit in their mouths. I feed my adult U. husbandi two to three times a week almost exclusively with medium-sized crickets and dubia cockroaches with occasional treats such as grasshoppers or other insects. For vitamin powder I use Repashy Calcium Plus* and I do not offer any loose calcium as in my experience they do not eat it.
U. husbandi do not react well to dehydration and therefore humidity is important. There is usually a little condensation in the wet box and it seems to me that the geckos mostly use that as their water source. Nevertheless, I occasionally spray the terrarium with water and they lick it up as well. Since this water supply seems to be sufficient, I have not offered a separate water bowl for years.
The geckos like to hide under and climb over pieces of cork, so I spread them around the terrarium. This species is also particularly suitable for bioactive terrariums, as many plants also thrive in the low temperature and isopods and other destruents feel very comfortable.
Underwoodisaurus husbandi do not have such a clear sexual dimophism as some Nephrurus species, but fortunately it is still easy to distinguish the sexes:
Males have very distinct hemipenis pockets that are easy to spot. Another sex distinguishing feature that I have never read about in the literature is the presence of waxy pores on the abdomen of males, which are visible at the latest when they reach sexual maturity.
I keep my U. husbandi separate and only introduce them in the mating season. In my experience, strict hibernation is necessary to prepare the geckos for breeding. For this I keep them at 10-16°C for about two months, but they can also tolerate cooler temperatures for a few days.
As soon as you put female and male together you will see if the geckos are interested in breeding because then the female will lie flat on the ground and the male will place a mating bite and they will mate. If the female is not ready, she will try to escape and the male will try to animate her by biting her body. The female will then express her displeasure with a very loud and shrill croaking noise - then you should separate the pair and try it again at another time.
If mating is successful, the developing eggs can be seen through the abdominal skin.
Watch out: The cool hibernation period seems to be necessary not only for initiating matings but also for fertilised eggs. If males don't want to breed, females don`t produce eggs, lay unfertilised eggs or the eggs turn bad during incubation, this is often due to a too warm hibernation and/or a lack of vitamins and minerals from the parents.
In very rare cases it can happen that individual eggs become too large and the females can no longer lay them. In this case, vets can aspirate the egg contents through the abdominal wall with a syringe. The females then excrete the empty egg shell after a few days. The intervention must be carried out professionally by a veterinarian, as it carries some risks. But then, as a minimally invasive method, it brings some health benefits and the female can continue to lay eggs.
The two eggs are laid in the coco peat of the wet box after a few weeks. Depending on the age and diet of the geckos, 4-6 clutches per year are possible.
I immediately transfer the eggs into an incubator. Incubation in perlite, vermiculite, seramis and "incubation above water" are suitable incubation methods. I mix perlite and vermiculite in a ratio of about 1:1 by weight with water. I incubate the Underwoodisaurus husbandi eggs between 27-28°C. At these temperatures the baby geckos hatch after 55-60 days. Temperatures above 30°C lead to many dead eggs, temperatures below 26°C extend the incubation period up to 70 days.
Already with hatching the Seidel albinos are very light - but do not have much colour yet. The pigmentation intensifies later and the colour potential of the gecko can usually only be seen when they have reached six to ten grams. The sex determination of geckos is clearly recognisable at the latest at ten grams. In some males, the hemipenises can be seen much earlier, but there are also "late bloomers" that come out much later. At 10 grams, however, it is already a very safe bet.
Taxonomic insights - is U. husbandi a valid species?
Underwoodisaurus is widespread in the southern half of Australia and I am quite sure that the genus will still have some surprises in store for us and more (sub)species will be described. In 2011, a second species besides U. milii was described as Underwoodisaurus seorsus by DOUGHTY & OLIVER.
But there is more:
Two forms of Underwoodisaurus milii are bred in the hobby, formerly called the "southern" and "eastern" forms. These forms can be distinguished fairly easily, as the southern ones have broad neck bands, a banded pattern and lighter colouration, while the eastern ones have rather fewer bands, more spots and darker colouration. Wells & Wellington described this "eastern" variant as Underwoodisaurus husbandi in 1983 in the "Australian Journal of Herpetolgy". The description does not meet the requirements of modern taxonomy and therefore this new species is still not accepted by the scientific community. But the side-by-side comparison shows clear differences between the two forms and several books* concentrating on herpetoculture also follow this logic. I have therefore decided that in order to distinguish the species/varieties well I 'm also using the names Underwoodisaurus milii and Underwoodisaurus husbandi. Hopefully, herpetologists will soon address this issue and provide scientific clarity.