Firebelly Facts Professional Opinion on the Fire Belly Morph of the Argentine Black and White Tegu (Tupinambis merianae) in Extreme Southern Mainland Florida

The following opinion is based upon current scientific data from peer-reviewed papers and the combined professional opinion of several experts in the field, including Florida Wildlife Commission personnel, University of Florida researchers and professors, USGS invasive species research group, and FKAA water quality specialist.

Also in agreement are well-known reptile breeders in Florida, Tom Crutchfield, Bob Freer, and Rachel Pikstein. Ms. Pikstein is a professional biologist with an M.S. degree in ecology and 25 years of experience in reptile husbandry. She is currently finishing a three-year genetic and ecological assessment of the Argentine Black and White Tegu that compares wild imported animals to both established exotic populations in Florida and to captive-bred individuals. Her sample size for this study is in excess of 600 lizards.

The aforementioned sources and current literature support the opinion that the lizards fitting the characteristics of a look that was coined as ‘fire belly’ by Rodney Irwin most likely represent a morph of unknown derivation whose intensity may or may not be influenced by environmental factors other than sunlight intensity.

The thick hide of a tegu has not been documented to absorb pigments from soil or leaf litter. Lizards with thick hides, such as teiids and varanids, are not known to be able to influence their body coloration by diet. Although some of the species have chromatophores, lizards of the genus Tupinambus are not known to have the ability to actively change color.

From combined observations of more than 3,000 tegus from the above mentioned sources, what is known is that juvenile characteristics fade away (green head/blue tail), and their natural colors brighten or darken during sexual maturity regardless of habitats and captive circumstances and subject to a variety of water sources, diets, and range of natural light or UVB bulb exposure.

The red coloration fades in the absence of natural sunlight in captivity or during brumation at breeding facilities when intense natural sunlight is removed. The fire belly is a morph whose intensity increases with exposure to natural sunlight.

Fire belly appears in <30% of the Homestead, Florida, population, where it is evident in males, females adults and juveniles. This morph also appears in captive-bred collections but with a lesser intensity of color. Less than 5% of animals showed red coloration in four breeding facilities examined by Pikstein. Fire belly is a heritable trait and occurs in approximately one-third of the small six-mile-radius introduced population in Homestead. Whether fire belly in its native range is a naturally-occurring morph or a regionally-distinct trait remains to be seen.

In captivity, however, the fire belly morph can be line-bred to select for the most intense trait or traits, as in the ‘blue tegu’ (Ron St. Pierre), ‘Chacoan tegu’ (Bobby Hill), ‘Bruiser’ and ‘Purple’ tegus (Rian Gitman of Underground Reptiles).

Hobbyists/breeders identify a unique trait and confirm it to be heritable through selective breeding and then coin the term to produce sales of that desirable morph within the species.

Regardless of hobbyist interest in its selective breeding, the fire belly is a morph.

In Homestead, that morph is present and maintained at its frequency through natural selection. In captivity, its fate will be determined by artificial selection.