Argentine Black and White Tegu

The Argentine black and white tegu is the largest of the tegu lizards, native to eastern and central South America, including south and southeastern Brazil, Uruguay, eastern Paraguay, Bolivia and Argentina. It lives in rain forests, savannas and semideserts, and appears to accept almost any habitat as long as it can burrow. Omnivorous, it eats insects, small birds, fish, frogs, rodents and fruit, and is a notorious egg predator. Adult males can exceed 120 cm in total length. Tegus enter brumation in autumn, and the species has become a problem invasive in Florida and Georgia.

About the Argentine black and white tegu

The Argentine black and white tegu is a large, omnivorous South American lizard in the family Teiidae, which also includes whiptails and racerunners. It is the largest of the tegus. It lives in forests, savannas and semideserts of Argentina, Brazil, Uruguay, Paraguay and Bolivia, and has become an invasive species in the southeastern United States.

Tegus fill a similar ecological role to monitor lizards such as the Komodo dragon, but they are only distantly related. The resemblance is a case of convergent evolution. The scientific name, Salvator merianae, honors Maria Sibylla Merian, a German-born naturalist and artist who studied insects, plants and reptiles.

Adults are heavy-bodied lizards with black and white banded and speckled patterns. Males are much bigger than females, often passing 120 cm (4 ft) and reaching 140 cm (4.5 ft) in total length. Females top out around 100 cm (3 ft). Males also develop big jowls from enlarged jaw muscles, while females keep a slimmer jawline. The skull is heavily built, and in large adults the rear teeth are bigger and more rounded than the front teeth.

Hatchlings look different. They are emerald green from the snout to midway down the neck, with black markings, and the green turns black over the next several months. Young tegus have yellow and black tail bands that fade into speckling with age, so fewer solid bands means an older lizard. The tail can be dropped as a distraction or swung at an attacker as a weapon.

Growth is fast. A hatchling weighs about 10 g (0.35 oz) and can reach 8 kg (18 lb) in four or five years, a nearly 800-fold increase. Tegus are sexually mature in their third year, at around 1.5 kg (3.3 lb), and stop growing by about their fourth.

Behavior and diet

Tegus are active by day in the warm months and spend the cold months brumating in burrows without eating. Here they do something remarkable for a reptile. During the breeding season, roughly September to December in their native range, they generate their own body heat, holding their temperature up to 10 °C (18 °F) above the surrounding air at night. It is one of the few lizards known to be partly warm-blooded, a trait also seen in some pythons during breeding, and the rest of the year tegus bask like ordinary reptiles.

The diet is broad. Young tegus eat insects, worms, crustaceans, spiders, snails, frogs, fish, small birds, other lizards, snakes, rodents and even armadillos, along with bananas, grapes, mangoes and papayas. Adults eat more plants, with vertebrate prey more common in spring and plants and invertebrates more common in summer. Tegus are notorious egg thieves, raiding the nests of birds and reptiles, including sea turtles, alligators and crocodiles.

Tegus can sprint fast and even run on their hind legs for short distances. In territorial displays they open their mouths and spread their front legs to look bigger. Lizards with stronger bites tend to stand their ground rather than flee.

Mating follows the spring emergence. Females track males by scent more intently than males track females, and males mark territory with gland secretions. Females build nests of dry grass, twigs and leaves and lay 18–25 eggs, sometimes more. Incubation averages 64 days, ranging from 40 to 75 depending on temperature, and eggs usually hatch in early spring.

Predators include cougars, jaguars, otters, snakes, caimans, birds of prey and the lesser grison, a weasel relative. Traffic is a serious threat too: it is one of the most frequently road-killed reptiles in its native range.

Range and habitat

The species is native to Argentina, south and southeastern Brazil, Uruguay, eastern Paraguay and Bolivia. It lives in tropical forest, savanna and semidesert, and also in scrub and wet habitats such as flooded savannas, canals, ponds and streams. It doesn't seem picky about habitat as long as it can dig a burrow. In central Argentina it hybridizes naturally with the red tegu.

Escaped and released pets from the early-2000s pet trade have founded invasive populations in Florida and Georgia, with sightings in South Carolina. Breeding has been confirmed in southeastern Florida, and established groups exist in Hillsborough and Polk counties. Adults can survive weather well outside their native climate, which raises concern about further spread.

The invaders threaten native birds and reptiles that nest or burrow on the ground. Nearly 3,300 tegus have been removed from Miami-Dade County alone, yet trapping and hunting have had limited effect. Florida now allows residents to kill tegus on private property with the landowner's permission and on public lands, and South Carolina has banned their import and breeding.

Argentine black and white tegu vs gold tegu

The gold tegu is sometimes sold as the "Colombian black and white tegu," and some pet dealers pass gold tegus off as Argentine tegus. For 154 years the two were even treated as a single species.

Conservation status

The Argentine black and white tegu is listed as Least Concern on the IUCN Red List. It is not endangered, even though it is one of the most heavily exploited reptiles in the world.

Tegus have long been hunted for their skins for the international leather trade, which is legal in most South American countries, and they are eaten as bushmeat in their native range. Overharvesting has not been observed. It is also one of the most frequently road-killed reptiles in its native range. Outside its range, the species is a conservation problem in its own right as an invader that eats the eggs of native wildlife, including the American alligator.