Argentine black and white tegu

The Argentine black and white tegu ("Salvator merianae"), also called the Argentine giant tegu, the black and white tegu, the huge tegu, and the lagarto overo in Spanish is a species of lizard in the family Teiidae. The species is the largest of the "tegu lizards". It is an omnivorous species which inhabits the tropical rain forests, savannas and semi-deserts of eastern and central South America.
Tegus are sometimes kept as pets. They are notable for their unusually high intelligence and can also be housebroken. Like other reptiles, tegus go into brumation in autumn when the temperature drops. They exhibit a high level of activity during their wakeful period of the year.
Tegus fill ecological niches similar to those of monitor lizards, but are only distantly related to them; the similarities are an example of convergent evolution.
Etymology.
The specific name, "merianae", is in honor of German-born naturalist Maria Sibylla Merian.
Description.
As a hatchling, "Salvator merianae" has an emerald green color from the tip of its snout to midway down its neck, with black markings. The emerald green becomes black several months after shedding. As a young tegu, the tail is banded yellow and black; as it ages, the solid yellow bands nearest to the body change to areas of weak speckling. Fewer solid bands indicates an older animal. A tegu can drop a section of its tail as a distraction if attacked. The tail is also used as a weapon to swipe at an aggressor; even a half-hearted swipe can leave a bruise.
Tegus are capable of running at high speeds and can run bipedally for short distances. They often use this method in territorial defense, with the mouth open and front legs held wide to look more threatening.
Adult males are much larger than the females and can reach 3 ft (92 cm) in length at maturity. They may continue to grow to lengths of 4.0–4.5 ft (120–140 cm).
The females are much smaller, but may grow up to 3 ft in length from nose to tail. They have beaded skin and stripes running down their bodies. Adult females can reach a weight of 2.5–7.0 kg (5.5–15.4 lb).
The skull is heavily built with a large facial process of the maxilla, a single premaxilla, paired nasals, a single frontal bone and a single parietal bone. Biomechanical analyses suggest the posterior processes of the parietal might be important for dealing with torsional loads due to posterior biting on one side. In the large adults, the posterior teeth are larger and more rounded than the anterior teeth.
Sex.
When a tegu reaches the age of 8 months, the beginning of their juvenile age, their sex can easily be determined visually; their vent at the base of the tail will bulge when it is a male and lie flat when it is a female. Breeders generally inform the buyer on the sex of the animal before the purchase. In adults, the main difference is in the jowls; adult males have substantially developed jowls (a result of hypertrophic lateral pterygoideus muscles), while females' jawlines are more streamlined.
Blue tegu.
The blue tegu is a variant known for its light blue coloration, which is most intense and vivid in the adult males. Even immature animals can be easily distinguished from other mostly black and white tegus by the "singe mark" on their nose. They are among the more suitable tegus for pets and can be easily tamed but, in the wild, will either try to run away or react aggressively if provoked. There is much controversy about the correct scientific classification of this animal. Large-scale taxon sampling of the teiids has not led to any strong resolutions based on morphological and genetic data; the majority of data about the blue tegu comes from hobbyists. Some believe it is a mutation of the Argentine black and white tegu, while others, including the original importer, believe it is sufficiently different to have its own classification. The first blue tegu to be exported from South America was in a wholesale shipment of tegus from Colombia.
The coloring of a blue tegu can range from a simple black and white color to albino to powder blue to even "platinum", which is basically a high white color morph. The colouration does not tend to appear until the animal reaches sexual maturity around the age of 18 months or it reaches 2 feet or more in size. Just like the Argentine black and white tegu, the blue tegu has a very quick growth rate, almost reaching 75% of its full length in 1 year. Their adult length can vary from 2.5 feet in adult females to sometimes even longer than 4 feet in adult males. Unlike other lizards, these are very heavily built animals, ranging from 7 to 12 pounds or more when fully grown. Size is relative to genetics as well as husbandry and diet.
Meat characteristics.
"S. merianae" - like a lot of animals used for bushmeat - is a common food source for humans in its native rangeand could be an economically and dietarily beneficial meat source if used more widely.
Epidemiology.
Almost all "S. merianae" at a captive breeding field station at the State University of Santa Cruz, Ilhéus, Bahia state, Brazil have salmonella, suggesting that it is common throughout Brazil.
Warm-bloodedness.
"Salvator merianae" has recently been shown to be one of the few partially warm-blooded lizards, having a temperature up to higher than the ambient temperature at nighttime;however, unlike true endotherms such as mammals and birds, these lizards only display temperature control during their reproductive season (September to December), so are said to possess seasonal reproductive endothermy. Because convergent evolution is one of the strongest lines of evidence for the adaptive significance of a trait, the discovery of reproductive endothermy in this lizard not only complements the long known reproductive endothermy observed in some species of pythons,but also supports the hypothesis that the initial selective benefit for endothermy in birds and mammals was reproductive.
Diet.
Tegus are omnivorous. Juvenile tegus in the wild have been observed to eat a wide range of invertebrates including insects, spiders and snails. They also eat fruits and seeds. As they grow, they become more predatory and the protein content of their diet rises. They may seek out eggs from other reptiles' and from birds' nests and will eat small birds and other vertebrates. In adulthood, tegus continue to eat insects and wild fruits and it is assumed that such components include desirable or essential nutrients.
In captivity, tegus commonly are fed high protein diets that include raw or cooked flesh such as ground turkey, canned and dry dog food, commercial crocodile diet, chicken, eggs, insects and small rodents. The inclusion of fruit in the diet is recommended. Though some captive tegus do not readily eat fruit, others enjoy bananas, grapes, mangoes and papayas. However, there is evidence that, as in most husbandry of carnivores, it is good practice to cook most of the egg in the diet, so as to denature the protein avidin that occurs in the albumen. Raw avidin immobilises biotin, so excessive feeding of raw eggs may cause fatal biotin deficiency.
As adults, they have blunted teeth and exaggerated lateral pterygoidal muscles which allow them to be generalist feeders. In captivity, they have been observed eating various feeder insects like mealworms, superworms, earthworms, silkworms, crickets and cockroaches, as well as vertebrate prey like mice, rats, fish, turkey (offered in a ground form), rabbit, quail and chicks. Crustaceans such as crayfish are also readily consumed. Like all lizards, blue tegus need a properly balanced diet; incomplete prey items such as insects or ground meat require dusting with a mineral/multi-vitamin supplement. Vitamin deficiencies can lead to trouble shedding skin, lethargy and weight loss; a calcium deficiency can lead to metabolic bone disease, which can be fatal.
Predators of tegus include cougars, jaguars, otters, snakes and birds of prey.
As household pets.
Tegus make amenable pets, as they tend to become acclimated to their owners and are generally quite docile as adults. They are intelligent and can even be housebroken. A healthy tegu can live for 15 to 20 years in the wild and possibly even longer in captivity. However, as with most reptiles, if they are not handled regularly, they show more aggressive behaviour; their bite can be painful and damaging due to strong jaws (1000 N bite force, stronger than a dwarf caiman, partly due to the short, deep skull) and sharp incisor teeth in the upper jaw. Tegus do not produce venom.
Tegus will perform a threat display if they are upset or stressed. The first stage is huffing, or very heavy breathing, which means "be careful". Further interference causes the animal to start lashing its tail, somewhat like a moving snake. In wild animals, a third stage of stamping the front feet or "dancing" is seen. If these hints are ignored, then the tegu can charge and may bite, which will require hospital or veterinary attention.
Captive husbandry.
To accommodate their size, a lone adult should be housed in nothing smaller than a 6'x3'x2' size cage, with the largest floor size possible. A pair of adults need double that size. They must have a lot of floor space. About six inches of substrate should be used to allow for burrowing, as well as a substrate that holds humidity well. Most owners use cypress mulch mixed with coconut fiber, as it retains humidity extremely well and is commercially available. Use only organic substrates, as anything with pesticides or additives, much like what you would commonly find at a hardware store, will cause many health issues with your tegu, including death. A good UVA and UVB bulb is imperative to keeping a tegu in good health. They need UVB to produce Vitamin D in their bodies, as well as metabolizing calcium. If they are not allowed exposure to UVB on a daily basis, they can experience severe pain and/or deformities from diseases such as metabolic bone disease. Along with UVB, a blue tegu also needs a temperature gradient. This means that one side of the cage must be cooler, while the other is much warmer and provides a basking spot. This is so they can regulate their body temperature by going to whatever temperature works for them at the moment. Ambient temperatures on the cooler side should be around 75 degrees Fahrenheit (23C) and the warmer side should be about 90 degrees Fahrenheit (32C). They also need the surface of their basking spot to meet specific temperature requirements. For juveniles and younger tegus, they need it around 100F (37C), though, as they get older, it can go up to 110F-120F (43C-48C). For healthy shedding, a humidity of 60-80% is preferred.
Like most lizards, fresh water should be provided daily. Like other tegu species, you should make sure your Argentine black and white tegu has enough water to soak in if they wish. Some tegu species are also known to enjoy swimming and, since they grow to about 1 meter long or more, a medium-sized to large cat litter box can be used as an appropriately sized water dish. Never allow the water level to be above shoulder height for a tegu, as many tegus commonly drown when left without supervision.
Distribution.
As the name would suggest, this tegu is native to Argentina, but also to Brazil, Paraguay and Uruguay.
Invasive distribution.
Argentine black and white tegus have also escaped from the pet trade in Florida and are now an invasive species in Florida, Georgia and South Carolina. The first sighting of "S. merianae" in Berkeley County, South Carolina was on September 10, 2020. Eight total sightings in South Carolina have been recorded as of September 10th, 2020.
Breeding.
Blue tegus, like other tegus, may breed up to twice a year. They only lay between 18 and 25 eggs in a clutch, sometimes more dependent upon animal size and husbandry as well as the individual health of the gravid female.
Taxonomy.
In 1839, this species of tegu was originally described as "Salvator merianae". However, beginning in 1845 and continuing for 154 years, it was confused with "Tupinambis teguixin" and was considered a synonym of that species. In 1995, it was again given species status as "Tupinambis merianae" because subsequent studies had shown that the gold tegu ("Tupinambis teguixin") was distinct from it. In 2012, the Argentine black and white tegu was reassigned to the resurrected genus "Salvator" as "Salvator merianae".
"S. merianae" is called the "Argentine black and white tegu" to distinguish it from the "Colombian black and white tegu", which is another name for the gold tegu. Unscrupulous or incompetent pet dealers sometimes pass off gold tegus as Columbian black and white tegus.
"S. merianae" and "T. teguixin" can be distinguished by skin texture and scale count:
In the ecotone between the arid Chaco and the Espinal of central Argentina, they are known to naturally hybridise with the red tegu ("Salvator rufescens") with a stable hybrid zone.