Scientific Input on Captive Management Issues: An Interview with Dr. Gary W. Ferguson

By Christopher V. Anderson & Gary W. Ferguson, PhD


Anderson, C.V. & G.W. Ferguson (2004). Scientific Input on Captive Management Issues: An Interview with Dr. Gary W. Ferguson. Chameleons! Online E-Zine, August 2004. (

Scientific research is of critical importance to a wide range of chameleon related topics. Much of the basis for captive management and breeding practices are directly developed from scientific studies. After publishing his recent book, “The Panther Chameleon: Color Variation, Natural History, Conservation, and Captive Management,” Dr. Gary W. Ferguson, a professor of biology at Texas Christian University, very graciously agreed to talk with us to expand on some of his research and the topics in his book.

Dr. Ferguson is well known for work on the ecology, behavior, evolution and nutrition of lizards. With chameleons, he is particularly known for his description of Chamaeleo (Trioceros) jacksonii xantholophus in 1988 with Eason and Hebrard and for his nutritional and behavioral studies of Malagasy reptiles, concentrating on the Panther chameleon, Furcifer pardalis. His demographic, nutritional and behavioral research on F. pardalis is of particular importance to chameleon breeders and we are pleased to have him discuss some of these topics with us.

[Anderson, Chris] Dr. Ferguson, in your research on chameleon nutrition and in breeding and raising chameleons, how have you approached the problem of providing for varying levels of nutritional need during the life cycles of your animals? Can you comment on the extent of variation in vitamin and mineral needs between reproducing females, adult males and growing juveniles and discuss your thoughts and methods for supplying sufficient nutrition?

[Ferguson, Gary W] Working over the past 15 years mostly with large numbers of individual panther chameleons at one time, I have tried to implement the most labor-saving techniques of provisioning. I keep all of my chameleons isolated in very simple open top plastic enclosures covered with a mesh lid and containing a simple climbing structure and no substrate. I normally feed all chameleons crickets and mealworms that are gut-loaded with a nutritionally formulated standard cricket diet from Zeigler Brothers Co., (Gardners PA). In addition, I try to provide them with a good fluorescernt ultraviolet B light source set up as a gradient and mist the sides of the cage daily. I maintain an overall enclosure temperature averaging about 85-88 degrees fahrenheit during the day dropping to the low 70's during the night. I try to feed them an amount of insects the equivalent of about 85% of the chameleon's body mass per week during the growing phase for both sexes and for reproducing adult females. I feed adult males about half as much. I usually feed 3 times per week. I do not usually "dust" the insects unless I have individuals beginning to show growth problems or mbd, which is rare and usually just in occasional individuals. Then I usually dust with a good mineral powder and sometimes with vitamin A (not Beta Carotene) powder about once every 2-3 weeks. This may or may not correct the problem. My approach is often known as the "minimalist approach" that is necessary when dealing with a large number of animals for research. It has proven successful for my purposes. I do not vary the diet quality significantly for juveniles gravid females etc.

I always recommend a large well ventilated and well planted terrarium for those keeping one or two singlely maintained chameleons. I do recommend substrate -free cage bottoms regardless of the complexity of the above-ground habitat. I also recommend supplementing with as big a variety of wild insects as feasible, when possible, something that can become very labor-intensive for large collections and carries some risks.

[Anderson, Chris] What are your thoughts with regard to the necessity of UVB lighting and the methods by which some chose to do without it? What would theoretically be required to provide sufficient calcium utilization in the absence of UVB lighting? Would you recommend the average keeper attempt such a method and what are your feelings with regard to the success potential of UVB absent nutrition with the majority of keepers?

[Ferguson, Gary W] Chameleons, like most vertebrates, including us, can obtain their vitamin D3 either from their diet or from UVB or a combination of the two. I prefer to keep the dietary vitamin D low and give them a gradient of UVB that is coordinated with a gradient of visible light. This is because my research over the last decade has shown that, if the UVB and visible gradients are correlated, panther chameleons have the ability to assess their own vitamin D-condition, see and respond to UVB radiation, and adjust their exposure to optimize their vitamin D condition. My currernt research focus is to demonstrate that this is something that many, if not most, diurnal basking lizards can do. There is no doubt that a "keeper" can decide that he/she will only use dietary vitamin D (dusting and/or gut-loading) and not UVB and can provide sufficient vitamin D from this source to maintain his animal in good vitamin D condition. However, there are two drawbacks to this approach. First, the decision for balancing the vitamin D provisioning shifts from the lizard to the keeper. Second, that person better know how much to provide because a dietary vitamin D overdose can cause vitamin D-intoxification that can disable or kill the animal. Alternatively, too much UVB can NOT cause vitamin D intoxification because the skin has mechanisms to shift to the production of biologically inert vitamin D-photoproducts, when necessary. Continuous strong UVB irradiance, that a lizard cannot escape, can cause skin damage and eventually malignant tumors, so that is why a gradient is important. The lizard must be allowed the opportunity to regulate its exposure.

Larry Talent at Oklahoma State University successfully raised multiple generations of panther chameleons by giving his animals carefully measured doses of vitamin D3 with no UVB and I have no doubt that other breeders have figured out effective doses with veiled and other chameleon species. Unfortunately, I do not recall the exact dose that Talent used and I haven't tried this approach extensively myself. Unless a novice has direct advice from an experienced breeder about the exact source and dose of vitamin D to use in the absence of UVB, I strongly recommend the use of one of the commercially available UVB-generating bulbs and low or no dietary vitamin D. A single (not double) 20 Watt Reptisun 5.0, or ESU desert 7%, or Sylvania 350 blacklight (not a GE or other brand blacklight which produce almost nothing but UVA) placed so the animal can get only as close as 10 inches from the bulb AND also can get away from it, will provide the proper UVB gradient for panthers Also, a 160 Watt Westron Active UV heat set up so the animal can get no closer than 30" to the bulb to prevent overheating should also work.

[Anderson, Chris] Even though your research has centered on Furcifer pardalis, have you encountered any justification for the increased occurrence of hypervitaminosis in “montane” species, such as Chamaeleo (Trioceros) jacksonii, etc., and can you mention any related nutritional practices of concern that keepers should be aware of? .

[Ferguson, Gary W] Even though I have not kept any of these in over a decade and was never successful at producing second generation captive offspring, I did formulate the opinion that the less dusting, the better for C. jacksonii and C. montium. I never got the long-term survival that many report (8+ years for c. jacksonii). I never kept them outside much nor gave them a large variety of insects, nor tried to manipulate cage humidity. I also never gave C. jacksonii very high UVB (I used Vita Lites), which could have been a problem. C. montium seemed to hide from UVB and do fine. I eventually gave them no UVB at all and got some successful reproduction of wild-caughts with low UVB and very little dusting. However, let me hasten to add that I am not a good source of information for succesfully keeping these species.

[Anderson, Chris] In your book you mention inbreeding and locality hybridization problems a number of times. While the basic theories behind the dangers of inbreeding are generally well understood, many question the true danger of such practices citing such cases as the C. jacksonii populations in Hawaii. While it would seem clear that this type of breeding should be avoided whenever possible, what are your thoughts on the true dangers of such bloodline management to the everyday keeper, to breeders and to the prospects of creating a largely self sustaining captive breeding population?

[Ferguson, Gary W]

Where to start!

Many people confuse the statements "inbreeding is bad" and "inbreeding depression is bad". Inbreeding depression is the expression of maladaptive or deleterious traits (traits that reduce evolutionary fitness and can increase the likelihood of death and or poor reproduction). If a species in the wild normally disperses and outbreeds (which is probably most species, including most chameleons), individuals of that species will contain a number of deleterious alleles that are a) in a heterozygous condition b) only expressed when in a homozygous condition. Inbreeding increases homozygosity. Therefore, inbreeding increases the expression of these bad traits.

C. jacksonii in Hawaii seems to me to be a clear case of what is called "the founder effect". With this effect the initial reproduction of a few founders represents inbreeding and random changes in the gene pool but effective population size within a few generations quickly exceeds the size where the effects of inbreeding (loss of heterozygosity and fixation of deleterious alleles) occur and natural selection of the fittest takes over. A genetic and phenotypic comparison between the Hawaiian and Mt. Kenyan C. jacksonii would probably reveal some interesting differences.

Let's say a breeder wants to develop a strain of leucistic chameleons. The leucistic allele or alleles are probably recessive AND, in terms of fitness in the wild, deleterious. The only way to get the expression of these alleles is through inbreeding. Hopefully, the alleles that result in leucistic color do not also effect survival and reproduction in a deleterious way. Probably some do and some do not. More importantly, a leucistic (or whatever) gene may prove to be hardy in combination with some overall genotypes but not with others. Breeder A ends up with a leucustic strain that is a "poor doer" and dies out. Breeder B ends up with a beautiful strain that is hardy generation after generation (a white mouse, so to speak). Both breeders start the same and may do exactly the same with breeder B just being lucky. But to increase your chances of being breeder B, you need to kind of follow what probably happened in Hawaii. Inbreed until your desired trait shows up (if it happens to be there at all). Then breed the carriers of that gene with as diverse a number of partners as possible to produce an array of genotypes in hopes that you will find the right genetic combination that may be both leucistic and "inbreeding-adapted". The key is to maintain a large breeding population so that you can "select" the hardy and "select against" the poor doer to continue your strain(s).

The bottom line is as follows. For the breeder who just wants to keep a continuing lineage of a particular chameleon and only keep a few individuals, you must make every attempt to outbreed. If you must inbreed, only do it for one or two generations max, always seeking unrelated partners each generation. If you want to develop high-dollar strains, you better have the resources to maintain a large colony (100+ breeders and several hundred offspring from which you will select AS AND AFTER THEY MATURE).Some of us have tried to have our cake and eat it too, i.e. inbreed with only a standing crop of a few breeders and few juveniles and we usually end up like breeder A.

Regarding "locality hybridization", with wide-ranging species, you may be dealing with several cryptic but full, reproductively-incompatible species. I believe this to be the case with panther chameleons and probably with F. oustaleti and F. lateralis in Madagascar and C. dilepis in Africa. The bottom line here is that the most likely best-possible result of interspecific hybridization of closely-related species is a hardy hybrid, but one that reproduces poorly or not at all (mule). So, breeders of wide-ranging species should always try to breed only individuals from the same localities, if they want multiple generations.

[Anderson, Chris] In your book, you began to present a standardized and quantitative analysis of the geographic locale variations in F. pardalis. These methods yielded an excellent comparison of male coloration in the examined localities but comparison of females proved more difficult and as you said, the findings “were not consistent enough to be diagnostic.” Determination of origin has long been a problem for keepers and breeders, especially with regard to females. Are further, similar studies currently being conducted with more locales and an effort to “decode” the female F. pardalis geographic variation? Could looking at the genetic variation over the geographical range of this and other species potentially create another, possibly more accurate method of determining a specimen's locale?

[Ferguson, Gary W] I don't know if anyone has tackled the female color/morphological variation in ernest yet. I hope someone does. Hopefully, there is some subtle scalation variation that will prove effective. Female panthers are so metachromatic that color alone may never prove very fool-proof. Genetics are definitely the way to go for accuracy but that will probably always be too labor-intensive and expensive for quick locality ID for the average breeder. If you have a couple of years, you can raise up offspring from a mother and check out the adult coloration of her sons, but that certainly isn't quick!

[Anderson, Chris] Dr. Ferguson, on behalf of myself, the rest of the Chameleons! E-Zine team and our readers, I'd like to thank you for taking the time to answer my questions. I hope that in the future you might be willing to participate in further interviews and possibly contribute as an author as well. Again, thank you for your time.

Christopher V. Anderson

Chris Anderson is a herpetologist currently working on his Ph.D. at the University of South Florida after receiving his B.S. from Cornell University. He has spent time in the jungles of South East Asia, among other areas, aiding in research for publication. He has previously traveled throughout Madagascar in search of, and conducting personal research on, the chameleons of the region. He has traveled to over 35 countries, including chameleon habitat in 6. Currently, Chris is the Editor and Webmaster of the Chameleons! Online E-Zine and is studying the kinematics and morphological basis of ballistic tongue projection and tongue retraction in chameleons for his dissertation. Chris Can be emailed at or

Gary W. Ferguson, PhD

Dr. Ferguson is a professor of Biology at Texas Christian University. He is well known for his work on the ecology, behavior, evolution and nutrition of lizards. With chameleons, he is particularly known for his description of Chamaeleo (Trioceros) jacksonii xantholophus in 1988 with Eason and Hebrard and for his nutritional and behavioral studies of Malagasy reptiles, concentrating on the Panther chameleon, Furcifer pardalis. His demographic, nutritional and behavioral research on F. pardalis is of particular importance to chameleon breeders and keepers.


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