Monday, July 28, 2008

A Chat With Dr. Gary W Ferguson

Photo courtesy of Dr. Gary W Ferguson

Dr. Gary W Ferguson is a renowned name in the world of herpetoculture. He is acknowledged for his scientific publications in the ecology, behavior, evolution and nutrition of lizards. He focuses his research on Panther Chameleons, Furcifer Pardalis. Dr. Ferguson's studies had helped many people in fine-tuning the proper environmental management for chameleons in captivity. Currently, he has just retired from teaching at Texas Christian University. But, he is still actively involved in herp-related researches.

My question in red
Dr. Ferguson's answer in blue

Interview date: February 29, 2008

1. What start your journey in chameleon studies, Dr Ferguson?
I had become fascinated by old world chameleons from books and pictures as a teenager. However, I never had a chance to see one until I was in graduate school in 1967. A student in a herpetology class I was taking brought in one that he had collected in Spain. My next contact with real chameleons came when the large pet-trade importation from Kenya began in the late 1970’s. Jim Murphy, curator of reptiles at the Dallas Zoo at that time, had purchased several for the zoo and some of the Jackson’s had babies. He donated a pair of babies to me at TCU in 1977 and the rest is history. I started my first scientific study of them in 1980 with a trip to Kenya. After another trip to Kenya in 1983 several of us published in 1988 the description of Chamaeleo jacksonii xantholophus from Mt. Kenya.

2. In your Panther book, you talk about 5-15uW/cm2 of UV-B for 12 hr/day. I've measured the levels at the basking site (Reptisun 5.0) and have kept the UV-B levels near your recommendation for my Panthers and Veiled chameleons for years with no problems. In addition, with good So Cal beach weather, they get to go outside (100-300uW/cm2) on weekends, weather permitting. Many of us are familiar with keepers/breeders who use MV UVB sources with levels 50-100uW/cm2 12hr/day that "appear" to be successful at keeping them for years at those levels and claim some visible benefits. I suspect that the chameleons are doing a decent job at regulating their exposure levels on their own. I'm sticking with your levels but I'm interested in anything you have to add to your previous conclusions!
-Q Dave Weldon-
One of the problems with measuring UVB irradiance is that different brands of meters give different readings from the same light source. The 5-15 recommendation was given at a time when we were using only Spectroline meters. The current spectroline meters (if indeed that are still available) are impractical for herpetoculture use because they read only in 10-microwatt increments, i.e. the resolution is poor for the low irradiances we are interested in. The more important recommendation was to provide a UVB source with maximum level that cause between 0.18 and 1.52 percent conversion of provitamin D to photoproducts in 2 hours in the ampules we have been using. Bill Gehrmann and I have been testing several meters to determine the relationship between readings and provitamin D conversion. The readings from the Solartech 6.2 meter that give the 0.18 to 1.52 percent conversion are about 10-50 microwatts per cm2. If the maximum source is higher and the lizards have an opportunity to photo regulate be moving in and out of the High UVB zones that is fine. That is what they do outdoors. Remember our study involved "involuntary doses" and the animals were on a low vitamin D diet. What they need will vary with diet and could vary between animals and populations.

3. We work hard to improve the CA-Ph ratio of our non-WC feeders. What research data is available on the Ca: Ph of the diet of wild chameleons?
-Q Dave Weldon-
There are no data that I am aware of regarding Ca P dietary intake in the wild. Most people assume that a 1.25-2:1 Ca: P ratio is good in the diet because that is approximately what you get in the blood of healthy animals. However, animals are probably pretty successful at regulating to those levels regardless of the intake ratio, providing the diet contains some of each compound and isn't too deficient in either. Let me hasten to add that I am not a physiologist or nutritionist, so this may not be a good explanation of things!

4. After reading your Thesis "Do Panther Chameleons Bask to Regulate Endogenous Vitamin D3 Production," I learned that chameleon in general produces its own D3 when exposed to Sunlight, what is your recommendation on supplementing vitamin D3 to chameleons in captivity- specifically to those who allows their chameleon to bask under the real sunlight for at least once a week? Is there a way to know how much do they actually need? Do chameleons have some kind of innate sense to avoid UVB when they have enough D3 in their body?
I recommend little to no dusting of insects with vitamin-mineral supplement containing Vitamin D3 unless the animals get no UVB. Even then, there is a risk of giving too much. Many of the commercial cricket feeds contain vitamin D3. I think that is ok to use those feeds regardless of the UVB environment of the chameleon. Crickets probably don’t gut-load enough from those feeds to cause vitamin D-toxicity. Unfortunately, dose-response studies for dietary vitamin D have not been systematically done like our dose-response study for UVB in the 2002 article. So, dietary requirements are mostly guesswork. However, Larry Talent successfully raised panthers to maturity without UVB and measured the dietary levels of vitamin D by injecting it directly into their mouths. I think I gave the recommended doses that he used in my book (oral solutions of Vitamin D3: 25 IU/week). I fully believe the claims of breeders who say they have raised and bred panthers with only dietary D. However, I do think that panther chameleons have a “sense” of their internal vitamin D-condition and can regulate their exposure to UVB accordingly. It makes a lot more sense to me to let the animals decide how to regulate their vitamin D-condition via exposure to UVB than us by guessing at appropriate dietary levels. If the chameleon fails to do this, I think it is because some artificial light sources confuse them. When the UVB source is in one part of the cage and visible light and heat is in another, they may have trouble judging the proper exposure. I have seen a couple of examples of this in large artificially lit zoo enclosures. While chameleons can burn their skin or their eyes with too much UVB or UVC (see Frances Baines website for info), they can’t harm themselves with overproduction of vitamin D. At some point of UVB exposure only inert photoproducts that aren’t toxic are produced in the skin.

5. As far as Chameleon's adaptation, I heard that some reptile species have pigmentation of the coelomic cavity and organs. The theory is that it helps absorb light and heat, or that it may help reflect solar radiation depending on the species. Is that also true for chameleon specifically for veiled and panther?

I have dissected a lot of panther chameleons and they do have some coelomic pigmentation but I can’t recall exactly how much and how it is distributed. Basking lizards in general do have dark pigmentation surrounding either the coelomic cavity or vital organs such as the gonads. Those that are more exposed to UV seem to have more, e.g. sun-loving vs. shade-loving anoles. In most cases that I am aware, these pigmentation layers can allow UVB penetration of the skin, which is where vitamin D synthesis takes place. There is a study of Kenyan chameleons by Al Bennett of U Cal Davis that shows that chameleons do alter their reflectivity of UVB of their skin somehow but the mechanism is not clear.

6. Since we are still in the topics of nutrition, what is your standing on the necessity of supplementing a preformed vitamin A VS beta-carotene?
I went through a period where I gut-loaded crickets with carrots but deprived them of preformed vitamin A and the chameleons developed vitamin A deficiency. This was surprising because humans can use beta-carotene for our vitamin A needs. So, I recommend using preformed vitamin A either as a direct supplement or in insect feeds.

7. Are you familiar with the reason why they cannot convert beta-carotene into Vitamin A? Also, how is it in the wild, they satisfy their need of Retinol? As a chameleon keeper, this topic seems to be controversial among people. Is there a more thorough study that addresses this matter?
I don’t know why the carotene in carrots couldn’t be converted. It could be that other carotenes in the guts of wild plant-eating insects can be. It could also be why panthers sometimes occasionally eat lizards and nestling birds, which should be a good source of retinol. I think it is a good idea to feed panthers large pinkies or small lizards, such as anoles, occasionally, if they will eat them. There indeed needs to be more study on this subject.

8. What is your recommended dosage of preformed Retinol for chameleon in captivity? Is there some kind of rules or some educated guess, for a lack of better words, to help chameleon keepers to sort out this confusion of varying degrees of nutrition requirements in an individual chameleon?
Larry Talent at Oklahoma State University gave his panthers 50 IU of retinol in corn oil solution once a week and had no A-deficiency symptoms.

9. Geophagy behaviors often found among the chameleon (Panthers and Veiled) in captivity and, unfortunately, very little is unknown of why this behavior often surface. My chameleon, regardless of all my attempts in enriching the feeder's nutrition and supplementation, is also one of the guys that practice this behavior (I sift the soil and throw away all the large lump to avoid possibility of impaction). In your opinion, what is the reason behind this behavior?
I have never witnessed geophagy or read about it, except one time. Once I witnessed a captive Parson's devour a shelf fungus that happened to be on a log in its cage. The only explanation that makes sense to me is that the animal senses some trace nutrient or mineral. A lot of lizards, e.g. geckos and Sceloporus, will lick mineral supplements out of a dish.

10. Why are there different colorations found in furcifer pardalis in different locality?
-Q Justin Carl-
The bottom line about color differences is, of course, I do not know. However, I speculate that in F. pardalis there has been a lot of population bottlenecking throughout the range and that differences among current populations in male coloration has resulted from evolution by genetic drift, i.e. I don’t think there is yet good evidence for adaptive evolutionary causes for the current differences. The more interesting color difference is the ability to rapidly change the entire head and body color during social displays in eastern populations and the more gradual seasonal changes in western populations that only allow rapid color change around the eye turrets and face. Eastern populations probably evolved in heavy rainforest habitat while the western populations probably evolved in more seasonal savannah habitat. In the east it may be more important for males to remain dark-colored most of the time to absorb heat when it is more overcast and only “brighten up” temporarily throughout their daily activity when they court or combat. Who knows? There are some interesting geographic difference in both F. oustaleti and F. lateralis. In both of these species the differences are more among the females than among the males. I think that F. pardalis, F. oustaleti and F. lateralis each represent a collage of yet-undescribed cryptic species that future taxonomists, using DNA data will discover.

11. I have always wondered about a certain behavior that chameleons display. Why do they go brighter and lighter during sleeping? In my simple reasoning, this seems to be contradictory to evolutionary behavior. Why go all the trouble camouflaging itself in the day and go bright during the night where some predators are active?
The behavior (movement, repositioning expansion etc.) of chromatophores (pigment bearing skin cells) is an energy dependent process. At night chameleons simply shut down the active process, chromatophore pigments contract, and the animal lightens. Because their natural nocturnal predators are not dependent on color vision, there has been no natural selection for them to maintain the active process while they sleep, just for them to save energy. We are new "color-vision" predators that exploit the conspicuousness that results when they are sleeping. Rest assured that should we be around long enough to exert significant natural selection, nocturnal cryptic coloration will possibly evolve in those exploited species (1000 to10, 000 generations or so down the line).

12. While we are still talking about panther colorations and locality, what are your thoughts on the practice of breeding different locality panthers?
Regarding the crossbreeding of color variants. I see no problem with herpetoculturist doing this. I have done a little of it myself. Since some of these crosses result in unsuccessful propagation, it is important in the buying, selling, trading game that it be crystal clear about which specimens are hybrids and which are not. Furthermore, if an animal is a hybrid it is important to know who the parents were, if it is a backcross etc. As genetic techniques and knowledge advances, herpetoculturists may be able to have simple genetic identity kits that allow identification of the genetic makeup of an individual of unknown history. This is still a long way off.

13. Regarding crossbreeding on panthers, many shunned the practice in defense of preserving the genetic traits and the possibility of reintroducing the specific locale species into the wild (in case the risk of extinction happened), what is your comment in regard to these thoughts?
Most of the breeding products of herpetoculture are done with the idea of the pleasures and profits of keeping herps in captivity. For this, “genetic purity” doesn’t need to be a high priority, although I think that keeping track of genetic heritage is always useful for promoting the industry and helping explain breeding anomalies. For the captivity-oriented breeders neither hybrids nor “pure” individuals should be reintroduced into wild populations because they are likely to be different genetically (i.e., more homozygous and/or possessing odd alleles or genotypes) from wild stock and could affect the natural gene pool. The idea of captive breeding with the purpose of reintroducing stock back into the wild involves different goals and dictates that breeding stock be kept as naturally pure (i.e. not hybridized with individuals from very different populations) but as heterozygous genetically as possible (i.e. not inbred). Such programs are a high priority among zoos with some involvement by universities and the private sector. Here studbooks and very rigorously controlled out breeding protocols are essential.

14. What is your advise for herp hobbyists in successful keeping of chameleon?
My advice to herp hobbyists just starting out on chameleons is to start small. Get one large juvenile or half-grown individual of a species known to be hardy in captivity from a reliable captive-breeding source. Do your homework before you purchase an animal. Make sure you are willing and able to get the proper setup before you purchase your animal. Be aware of animal's light, temperature and humidity requirements. Be prepared to devote quality time daily to your animal so you can get to know the subtle signals that all is well or not well. However, do not over-react to perceived signs of distress. Healthy chameleons are pretty tough. Bigger is not always better with regard to food, vitamin-mineral supplements, cage-size, cage-ornamentation etc. In general, plan to keep your chameleon one animal per cage. Enjoy your experience and don't be too frustrated if your first chameleon doesn't do well. Be aware that they can become addictive. You may catch the dreaded disease: Chameleophilia!

15. What next for you, Dr. Ferguson? Any new research or new books coming out?
As a new retiree from academia and having a relatively healthy 67-year old mind and body, I plan to remain active in herp research for as long as possible. My current interest is in ultraviolet light and behavioral UV-vitamin D photo regulation, i.e. increasing our understanding of how lizards and snakes perceive and utilize ultraviolet light to regulate their vitamin D-condition. I am working with the Fort Worth and Dallas Zoos and with several colleagues to focus on ultraviolet cage environments. Basically, we are collecting and using data from lizards and snakes in the wild to document the normal UV exposures in their various types of environments. From this we are establishing guidelines for setting up UV sources and gradients in larger and smaller enclosures. We are working closely with Frances Baines and Steve Makin to evaluate artificial light sources and solartech meters. We plan to establish a detailed set of guidelines for the zoo and herpetoculture community on the proper use of UVB for various species. Stay tuned for the fruits of our labors.

Thank you Dr. Ferguson for this wonderful opportunity and your insightful answers.
I wish you more success for your researches.
Cannot wait for your new books! :)
Thanks, Frans; It has been fun ! I like your blog !

3 comments:

BobMac said...

Just a great interview. Gary had told me that he was retiring but it’s wonderful to see that he is still very active in the research field and working with Frances Baines! Thank you for the work.

BobMac
RUV

Frans Kusuma said...

Hi Bob,
I am glad you like the interview. Dr. Ferguson is a very amazing and nice man. The interview went so well. I could not asked a better experience than this.

Anonymous said...

Instructive, very interesting and meaningful questions! Thank you for sharing this!