The Argentine tegu is a lizard that warms its own body when breeding
Reptiles are supposed to rely on the sun for warmth, but during the breeding season the Argentine black and white tegu generates some of its own heat. It is the only known reptile outside birds to be partly warm-blooded, and it is now spreading through Florida.
Salvator merianae is the largest of the tegus, native to Argentina, Brazil, Paraguay, Bolivia and Uruguay, where it lives in rainforest, savanna and semi-desert. Tegus fill a niche much like monitor lizards, but the two are only distant relatives, a case of convergent evolution. Keepers prize them for unusual intelligence and a fairly calm temperament. Males can top 120 cm including the tail and develop heavy jowls from enlarged jaw muscles; females are smaller and sleeker. Hatchlings start with an emerald-green head that turns black within months, and the yellow tail bands fade to speckles with age, so fewer solid bands signal an older lizard.
Growth is dramatic. A hatchling weighs about 10 g and can reach 8 kg within four or five years, a nearly 800-fold increase, maturing in its third year. Tegus are active through the hot months and brumate, a reptilian form of dormancy, when it turns cold. They eat almost anything, from snails and spiders to rodents, armadillos and mangoes, and they are notorious egg thieves. Individuals with a stronger bite tend to stand and fight rather than flee, a trade-off more typical of mammals.
Naming it caused a century and a half of muddle. Described in 1839, it was lumped with the gold tegu from 1845 for 154 years, restored as a species in 1995 and moved to the revived genus Salvator in 2012. Its species name honours the German-born naturalist and artist Maria Sibylla Merian, and some dealers still sell gold tegus under its name.
Escaped or released pets from the early 2000s have established breeding populations in Florida and Georgia, with sightings in South Carolina. Researchers tracking a Florida female to her nest mound found a fresh clutch of 21 eggs. Because tegus raid nests, they threaten sea turtles, alligators and crocodiles, and they seem able to survive well outside their native climate.
Source: Argentine black and white tegu
