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Gary Ferguson
Professor Emeritus
Program Affiliations
Education
- 1963 B.S., Tulane University
- 1965 M.S., Texas Tech University
- 1969 Ph.D., University of Michigan
Areas of Focus
- Evolution of Life history traits of reptiles, particularly egg and clutch size of
females
Vitamin D deficiency and treatment of captive reptiles
Ultraviolet B radiation exposure, vitamin D photo-biosynthesis and behavioral regulation of vitamin D status by reptiles
As a herpetologist and behavioral ecologist mentored by Donald Tinkle, a leading reptile
ecologist of the mid-20th Century, I began research by investigating how nutritional
and predatory environmental pressures on lizard populations shape the evolutionary
trajectory of traits such as the age of maturity, offspring number, and offspring
size during reproduction. My colleagues, students, and I monitored birth, growth,
and survival within free-living lizard populations for multiple generations using
mark-recapture techniques. We also manipulated nutrition and predation within these
populations. We concluded that high predation favors early maturity, a shorter generation
time of the population, and the production of more but smaller offspring. Lower predation
favors more crowding, greater food competition, delayed maturity, and producing fewer
but larger, more competitive offspring.
My lifelong fascination with Old-World Chameleons, and close collaboration with colleagues from the world-class captive reptile collections at the Dallas and Fort Worth Zoos, resulted in a mid-career change of focus to a long-standing Question among Zoo herpetologists, “Why are Old-World Chameleons so difficult to keep in captivity”?
After 30 years of research on chameleons both in the field and in captivity, we conclude that: 1) many chameleon species are naturally short-lived and (2) most species require exposure to sunlight, specifically, to the natural exposure to Ultraviolet B radiation, to grow and reproduce successfully. UVB exposure is difficult to deliver to captive reptiles maintained indoors in terrariums. Therefore, many captive reptiles have suffered from calcium deficiency, skeletal growth deformities, reproductive failure, and premature death. Studies on humans with similar health disorders have shown that calcium deficiency results from vitamin D deficiency, which reduces calcium uptake from the diet. Our research has documented that panther chameleons and other diurnally active lizard species perceive UV radiation and behaviorally regulate their exposure, depending on their circulating vitamin D status. Supplementary dietary vitamin D causes the lizards to expose themselves less to UVB. Conversely, dietary vitamin D deficiency causes them to prolong exposure to UVB. These findings have resulted in substantial advances in herpetocultural technology and success in captive propagation. New programs requiring the successful propagation of reptiles and amphibians and with educational and conservation objectives have benefitted.
My recent research focus has been documenting the natural UV exposure of various reptiles and developing field monitoring techniques. Results from these studies provide a valuable guide to appropriate light environments in captivity. TCU’s mascot, the Texas horned lizard, has been the subject of two recent studies in collaboration with the Texas Parks and Wildlife Department and Dallas Zoo.
My lifelong fascination with Old-World Chameleons, and close collaboration with colleagues from the world-class captive reptile collections at the Dallas and Fort Worth Zoos, resulted in a mid-career change of focus to a long-standing Question among Zoo herpetologists, “Why are Old-World Chameleons so difficult to keep in captivity”?
After 30 years of research on chameleons both in the field and in captivity, we conclude that: 1) many chameleon species are naturally short-lived and (2) most species require exposure to sunlight, specifically, to the natural exposure to Ultraviolet B radiation, to grow and reproduce successfully. UVB exposure is difficult to deliver to captive reptiles maintained indoors in terrariums. Therefore, many captive reptiles have suffered from calcium deficiency, skeletal growth deformities, reproductive failure, and premature death. Studies on humans with similar health disorders have shown that calcium deficiency results from vitamin D deficiency, which reduces calcium uptake from the diet. Our research has documented that panther chameleons and other diurnally active lizard species perceive UV radiation and behaviorally regulate their exposure, depending on their circulating vitamin D status. Supplementary dietary vitamin D causes the lizards to expose themselves less to UVB. Conversely, dietary vitamin D deficiency causes them to prolong exposure to UVB. These findings have resulted in substantial advances in herpetocultural technology and success in captive propagation. New programs requiring the successful propagation of reptiles and amphibians and with educational and conservation objectives have benefitted.
My recent research focus has been documenting the natural UV exposure of various reptiles and developing field monitoring techniques. Results from these studies provide a valuable guide to appropriate light environments in captivity. TCU’s mascot, the Texas horned lizard, has been the subject of two recent studies in collaboration with the Texas Parks and Wildlife Department and Dallas Zoo.
- Ferguson, G.W. and S.F. Fox. 1984. Annual variation of survival advantage of large juvenile side-blotched lizards, Uta stansburiana: its causes and evolutionary significance. Evolution 38:342-349.
- Ferguson, G. W., J.R. Jones, W.H. Gehrmann, S.H. Hammack, L.G. Talent, R.D. Hudson, E.S. Dierenfeld, M.P. Fitzpatrick, F.L. Frye, M.F. Holick, T.C. Chen, Z. Lu, T.S. Gross, J.J. Vogel. 1996. Indoor husbandry of the panther chameleon Chamaeleo (Furcifer) pardalis: effects of dietary vitamins A and D and ultraviolet irradiation on pathology and life-history traits. Zoo Biology 15:279-299.
- Ferguson, G.W., W.H. Gehrmann, K.B. Karsten, S.H. Hammack, M.McCrae, T.C. Chen, N.P. Lung, M.F. Holick. 2003. Do panther chameleons bask to regulate endogenous vitamin D3 production? Physiological and Biochemical Zoology 76:52-59.
- Karsten, K.B., G.W. Ferguson, T.C. Chen, M.F. Holick. 2009. Panther chameleons, Furcifer pardalis, behaviorally regulate optimal exposure to UV depending on dietary vitamin D3 status. Physiological and Biochemical Zoology 82:218-225.
- Ferguson, G.W., W. H. Gehrmann, A.M. Brinker, G.C. Kroh, D.C. Ruthven III. (2015) Natural UVB exposure of the Texas horned lizard at a north Texas wildlife refuge. Southwestern Naturalist 60(2-3):231-239.
- Ferguson, G.W., W.H Gehrmann, M.Vaughan, G.C.Kroh. D.Chase, K.Slaets, M.F.Holick.2021. Is the natural UV zone important for successful captive propagation of the Panther Chameleon: (Furcifer pardalis); are different UVB irradiance exposures that generate a similar dose equally successful? Zoo Biology. 40:150-159.
- Ferguson, G.W., B. Lawrence, R. Hartdegen. (2023) Annual, seasonal, time of day, age, sexual, and gestational variation of Ultraviolet-B exposure of free-living Texas Horned Lizards Phrynosoma cornutum in Central Texas: a 10-year study. Herpetological Review. 54:27-31.
- NSF Predoctoral trainee (1965)
- NIH Predoctoral Fellow (1964-66)
- Naval Medical Research Institute Fellow (1962)
- Smithsonian Institution Postdoctoral Fellow (alternate) (1974)
- Nominee, President-elect, Society for the Study of Reptiles and Amphibians (1976)
- Summer Research Fellow, Savannah River Ecology Laboratory (1977)
- President Texas Herpetological Society (1985)
- Invited Banquet Speaker - Northern California Herpetological Society
- Mortar Board Preferred Professor (1993-94, 2003)
- Deans research award, TCU (2006)
- Keynote speaker, Advancing Herpetological Husbandry (2019), Zoo Med, Inc., (January 2020)
- Texas Herpetological Society, President 1985
- American Institute of Biological Science
- Ecological Society of America
- American Society of Ichthyologists and Herpetologists, Board of governors, Time and Place Committee
- Society for the Study of Reptiles and Amphibians*
- Society for the Study of Evolution
- Herpetologists League, Board of Councilors
- Sigma Xi
- Southwestern Association of Naturalists*
- Chicago Herpetological Society*
- *current affiliations
Last Updated: November 19, 2024