Home | Field studies and notes | Has Anyone Observed This?….. Madagascar and Standing’s Day Geckos (Phelsuma madagascariensis grandis, P. m. madagascariensis, P. standingi) maintain excellent health and reproduce without a UVB source

Has Anyone Observed This?….. Madagascar and Standing’s Day Geckos (Phelsuma madagascariensis grandis, P. m. madagascariensis, P. standingi) maintain excellent health and reproduce without a UVB source

It is well known that many species of lizard, turtle and crocodilian require ultraviolet light of a specific wavelength (290-310 nanometers) in order to synthesize Vitamin D3.  This vitamin, in turn, allows the reptiles to make use of the calcium in their diets.  Such reptiles (which generally bask in the sun in the wild) develop calcium deficiencies and a host of related problems if denied UVB in captivity.  This occurs despite their being offered a diet high in calcium.

Day geckos of the genus Phelsuma seem to require quite high levels of UVB in captivity.  Several species, and gravid females in particular, develop bulging “chalk sacs” (calcium stores) behind the head, and are quick to succumb to health problems in the absence of UVB.

Some years ago, however, I observed a situation that caused me to question what I knew, or thougMadagascar Giant Day Geckoht I knew, about this subject.  A number of Madagascar, Madagascar Giant and Standing’s Day Geckos were released into a densely-planted indoor “rainforest” in NYC’s Central Park Zoo.  The lizards thrived and reproduced, and, when last I checked, had been doing so for several generations.  Animals that are captured from time to time exhibit excellent bone density and overall good health, despite the fact that they have no access to natural or artificial UVB.

The aviary in which they live supports a wide variety of spiders, beetles, roaches, sow bugs and other invertebrates, as well as nectar and fruit producing plants.  I imagine that the lizards, amid this banquet, have found a source of calcium that is usable in the absence of UVB, or D3 that can be absorbed from the diet.  I will keep you posted as to further developments.

I have since spoken with lizard-keepers who maintain day geckos without UVB.  However, as we know little of the interaction between calcium, phosphorus and Vitamin D3 in these animals, a good deal of experimentation is needed, and the results are spotty.  The lizards at the Central Park Zoo are the most robust I’ve seen, and the population has remained so for 15 years or more at this point.

Red-eared Sliders, Chrysemys picta elegans, also suffer from calcium deficiencies if unable to bask under a UVB source – yet I know of a number of instances in which perfectly formed specimens were raised without such.  Again, I can only guess as to the explanation.

I tend to encourage dietary variety in my nutrition articles, due in part to experiences such as described above.  We really know very little about many common reptiles and amphibians, especially concerning nutrition.  I would greatly appreciate hearing about experiences you may have had – good or bad – regarding UVB light and diet.

The abstract of an article about Zoo Zurich’s “free-ranging” colony of Madagascar Giant Day Geckos is posted at:



  1. avatar

    I think Ed Kowalski(sp.) said that anoles and other lizards traditionally thought to need UVB can be kept and bred as long as they are supplied calcium with vitamin D3 added.

    This requirement for UV light has been the main reason I’ve stayed away from reptiles. I can’t out of good conscience replace expensive light bulbs every few months when they look perfectly fine to the naked eye!

  2. avatar

    Hello, Frank Indiviglio here. Thanks for your interest in our blog.

    Yes, some anole species can be kept without UVB if careful attention is paid to the diet….and you can rely completely on anything you learn from Ed Kowalski.

    I know of a pair of knight anoles that did very well and bred under conditions I would normally consider less than ideal. Their diet included, among other things, 3 species of roach and an occasional Carolina anole, along with super mealworm beetles, and a nectar-fruit mix with vitamins. They were adults when put into the situation, so UVB might have been less of a concern, but still noteworthy I believe.

    I know what you mean re discarding bulbs! One solution is to purchase a small UVB meter…output and life varies greatly even among bulbs from the same manufacturer…a meter will allow you to get the most out of the “stronger” bulbs, and to move those that weaken to situations where they can be brought in closer contact with basking sites, thereby increasing their useful life somewhat.

    Best regards, Frank Indiviglio.

  3. avatar

    Hi Frank,

    I am enjoying my tour of your Blog much.

    Though out in our home often, my Giant Day seems to suffer no ill consequences. He has learned to be difficult to catch. Will go 3 to 4 months and remain in great health! Will take worms from a set of tongues and drop down to the tops of other tanks for heat and to eat a fruit mix. Bananas being a favoured. He has been here for 7 years now, was full grown when he got here, and has likely spent a minimum of a year and a half on the walls.

    • avatar

      Hello Pat, Frank Indiviglio here. Thanks so much for your kind words and interest in our blog.

      I really appreciate your taking the time to write in with this interesting tidbit…I’ll add it to my notes on the topic. We have a great deal to learn, and your observations will be very helpful in that regard.

      The holding rooms of most zoos are occupied by day geckos of 1 species or another, and several are well-established in areas adjoining Florida importers’ facilities. They are just too fast, and do, as you say, learn how to avoid capture. Years ago a store in NYC tried renting Tokay geckos for release into roach-ridden apartments, but their agility in avoiding capture (and the males habit of calling at 4 AM) led to the project’s demise!

      Good luck and please keep me posted on other observations.

      Best regards, Frank Indiviglio.

  4. avatar

    Hi, Idon’t know if you’ll get this on time, but my hope lies here. My gecko’s butthole is prolasped,I don’t know what to do.He won’t eat, and it breaks my heart.What should I do???? Just this past week it has been very confusing and fusterating because of just that. Please any sort of helping information would be greatly appreciated, I’m not ready to just give up on him. Thank you.

    • avatar

      Hello, Frank Indiviglio here.

      Thanks for your interest in our blog.

      Please see this article: Amphibian and Reptile Emergencies for some emergency steps you can try at home; however, if the prolapse occurred more than 1-2 days ago, you’ll need to bring the lizard to a veterinarian. Please write back if you need a reference to a reptile veterinarian in your area; I’ll do my best to find someone for you.

      Good luck and please keep me posted.

      Best regards, Frank Indiviglio.

  5. avatar

    Hello Frank, apologies for posting in such an old topic but this recent thread might interest you. It regards anecdotal experience variety of turtle species(box, wood, painted, musk, etc.) raised without any exposure to UV whatsoever(and according to him, doing well, otherwise I wouldn’t report it!)

    • avatar

      Hello Joseph,

      Thanks for sending this along; important topic and a frequent source of questions. I too have run across turtle species that normally bask (sometimes called heliothermic species) but which did fine when raised without UVB…however, these are exceeded by the millions of turtles that did not survive such conditions. I’m fairly certain that it has to do with how D3 is presented in the diet; anecdotally, it seems that some turtles can utilize dietary D3 even though they generally bask in order to manufacture D3.

      Chameleons have been shown to increase their exposure to UVB when fed D3-deficient diets, so there must be more flexibility that we imagine. A varied diet, or one high in the right foods, is useful. Many of the poor results seen w/o UVB likely involve animals fed on inappropriate diets as well.

      The heliothermic turtles I’ve most often observed to do well without UVB have been red eared sliders (no surprises there!). I ran into a zoo visitor who fed her slider 2-3 “Mentos” candies every day – the turtle was over 20 yrs old and, from the photo I saw, appeared to be in good shape – so all bets are off with those guys!

      Mud, musk, snapping, pig-nosed and softshell turtles all apparently rely mainly on dietary D3, and do fine without UVB.

      As was mentioned in the post you referenced, UVB is a safety net for most species; I always suggest it, even for the largely aquatic species mentioned above, as it is surer option than relying on a varied diet, and also easier for most folks.

      Good luck and please keep me posted.

      Best regards, Frank Indiviglio.

  6. avatar

    I bred turtles and anoles without any uv… however the growth is sligthly lower.. fishy terrain here and I would be burned in most forums.


    • avatar

      Hi Pedro,

      I know what you mean! I’m always on the lookout for relevant research – but certainly there is more to D3 and its metabolism than we imagine. Overall diet, form in which D3 is ingested, etc., could all be important. Some chameleons can also utilize dietary D, although providing UVB and dietary D is the safest route to follow; this article describes how they regulate sun exposure in accordance with D3 levels, and mentions dietary as well. Best, Frank

  7. avatar

    A bit off topic but regarding your experience with that population of day geckos in a indoor habitat, that has been as well my past experince with greenhouses and many different lizards. Some of the most beautifull day geckos, anoles, basilisks, iguanas, agamids, etc, that Ive seen were raised in greenhouses. That is as well a very eco friendly way to raise these animals, even in colder climates. However even here most keepers ignore the advantages of it. Reptile greenhouses seem to be more popular in the Netherlands and Sweeden, as well as specialty made indoor-outdoor enclosures. My question would be, has the zoo world ever considered incorporated that same design of population management into some rare day geckos? I mean there are many day geckos that are very rare in captivity and some that aren´t doing that well, like I know some species have screwed gender ratios and nobody is shure why. I know that zoos have recently showned interest into day geckos and that some rarer ones were aquired from privates in Europe. I would love to see such displays becoming more popular, none the least considering how easy they are to keep.


    • avatar

      Hi Pedro,

      Some private hobbyists do well with other lizards in greenhouses here as well; regular glass is used (glass that emits UVB is available, but expensive); there have been various discussions re using botanical gardens, greenhouses in zoos as sites to rear geckos, rare amphibs, etc,, but red tape, costs etc seem to get in the way; the Bronx Zoo is building an off-exhibit amphibian building, as are some others ; (amphibs seem to take preference in such plans these days) but animals that draw crowds are given preference; most zoos cannot afford to focus on others, best, Frank

  8. avatar

    In their book, Day Geckos in Captivity, Greg and Leann Christenson write extensively about maintaining Phelsuma without UVB and using Calcium with D3 instead. Following their advice, I have maintained a P. laticauda for 8 years and a P. klemmeri for 7 years with calcium/D3 supplementation. Both are females, have large calcium cheek pouches and are in excellent health.

About Frank Indiviglio

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Being born with a deep interest in animals might seem unfortunate for a native Bronxite , but my family encouraged my interest and the menagerie that sprung from it. Jobs with pet stores and importers had me caring for a fantastic assortment of reptiles and amphibians. After a detour as a lawyer, I was hired as a Bronx Zoo animal keeper and was soon caring for gharials, goliath frogs, king cobras and everything in-between. Research has taken me in pursuit of anacondas, Orinoco crocodiles and other animals in locales ranging from Venezuela’s llanos to Tortuguero’s beaches. Now, after 20+ years with the Bronx Zoo, I am a consultant for several zoos and museums. I have spent time in Japan, and often exchange ideas with zoologists there. I have written books on salamanders, geckos and other “herps”, discussed reptile-keeping on television and presented papers at conferences. A Master’s Degree in biology has led to teaching opportunities. My work puts me in contact with thousands of hobbyists keeping an array of pets. Without fail, I have learned much from them and hope, dear readers, that you will be generous in sharing your thoughts on this blog and web site. For a complete biography of my experience click here.
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