Argentine black and white tegu

The Argentine black and white tegu (Salvator merianae), also called commonly the Argentine giant tegu, the black and white tegu, the huge tegu, and in Spanish as the lagarto overo[1] is a species of lizard in the family Teiidae. The species is the largest of the "tegu lizards".[4] It is an omnivorous species which inhabits the tropical rain forests, savannas, and semi-deserts of eastern and central South America.

Argentine black and white tegu
Male
Female

Least Concern  (IUCN 3.1)[1]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Family: Teiidae
Genus: Salvator
Species:
S. merianae
Binomial name
Salvator merianae
Synonyms[3]
  • Salvator merianae
    A.M.C. Duméril & Bibron, 1839
  • Teius teguixim
    — Gray, 1845
  • Tupinambis teguixin
    — Boulenger, 1885
  • Tupinambis merianae
    — Dirksen & De la Riva, 1999
  • Salvator merianae
    — Harvey et al., 2012

Tegus are sometimes kept as pets. They are notable for their unusually high intelligence and can also be house-broken. 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, and are an example of convergent evolution.

Etymology

The specific name, merianae, is in honor of German-born naturalist Maria Sibylla Merian.[5]

Description
A black and white tegu seen in Florianópolis, Santa Catarina, Brazil.

As hatchlings, 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 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).[6]

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.[7] In the large adult animals, the posterior teeth are larger and more rounded than the anterior teeth.[8]

Warm-bloodedness

Salvator merianae has recently been shown to be one of the few partially warm-blooded lizards, having a temperature up to 10 °C (18 °F) higher than the ambient temperature at night time.[9] 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,[10] but also supports the hypothesis that the initial selective benefit for endothermy in birds and mammals was reproductive.[11][12]

Diet

Tegus are omnivorous. Juvenile tegus in the wild have been observed to eat a wide range of invertebrates, including insects, spiders, and snails.[13] 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 & 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 really enjoy banana, grapes, mango, and papaya.[14] 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.[15]

Predators of tegus are pumas, otters, jaguars, 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 house-broken. 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/veterinary attention depending on the victim.

Taxonomy
The two prominent loreal scales between the eye and nostril of this black and white tegu, plus its round pupil, identify it as belonging to the genus Salvator.

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, is distinct from it. In 2012, the black and white tegu was reassigned to the resurrected genus Salvator as Salvator merianae.[16]

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 black and white tegus.

S. merianae and T. teguixin can be distinguished by skin texture and scale count:

  • S. merianae has two loreal scales between eye and nostril.
  • T. teguixin has only a single loreal scale between eye and nostril.
  • S. merianae has round pupils, whereas Tupinambis species have reniform pupils.
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See also

References
  1. Embert D, Fitzgerald L, Waldez F (2010). "Salvator merianae". IUCN Red List of Threatened Species. 2010. Retrieved 22 January 2015.
  2. Duméril AM, Bibron G (1839). "Le sauvegarde de Mérian, Salvator Merianæ, Nobis". Erpétologie générale ou Histoire naturelle complète des reptiles. 5. Paris: Roret. pp. 85–90.
  3. "Tupinambis merianae". The Reptile Database. www.reptile-database.org.
  4. www.wildherps.com
  5. Beolens, Bo; Watkins, Michael; Grayson, Michael (2011). "Tupinambis merianae". The Eponym Dictionary of Reptiles. Baltimore: Johns Hopkins University Press. p. 175. ISBN 978-1-4214-0135-5.
  6. http://www.uco.es/organiza/servicios/publica/az/php/img/web/17_12_32_15NotaRendimientoBasso.pdf p. 346
  7. Jones ME, Gröning F, Dutel H, Fagan MJ, Evans SE (2017). "The biomechanical role of the chondrocranium and sutures in a lizard cranium". Interface. 14: 20170637. PMID 29263126.
  8. Presch W (1974). "A survey of the dentition of the macroteiid lizards (Teiidae: Lacertilia)". Herpetologica. 30 (4): 344–349. JSTOR 3891430.
  9. Tattersall GJ, Leite CA, Sanders CE, Cadena V, Andrade D, Abe AS, Milsom WK (2016-01-22). "Seasonal reproductive endothermy in tegu lizards". Science Advances. 2 (1): e1500951. doi:10.1126/sciadv.1500951. PMC 4737272. PMID 26844295.
  10. Hutchison VH, Vinegar A (1966). "Thermoregulation in a brooding female Indian Python, Python molurus bivittatus ". Science. 11 (3711): 694–695. doi:10.1126/science.151.3711.694. PMID 5908075.
  11. Farmer CG (2000). "Parental Care: The Key to Understanding Endothermy and Other Convergent Features in Birds and Mammals". American Naturalist. 155 (3): 326–334. doi:10.1086/303323. PMID 10718729.
  12. Farmer CG (2003). "Reproduction: The Adaptive Significance of Endothermy". American Naturalist. 162 (6): 826–840. doi:10.1086/380922. PMID 14737720. S2CID 15356891.
  13. Colli GR, Péres AK Jr, da Cunha HJ (1998). "A new species of Tupinambis (Squamata: Teiidae) from Central Brazil, with an analysis of morphological and genetic variation in the genus". Herpetologica. 54 (4): 477–492. JSTOR 3893442.
  14. Kiefer, Mara C.; Sazima, Ivan (2002). "Diet of Juvenile Tegu Lizard Tupinambis meriamae (Teiidae) in Southeastern Brazil." Amphibia-Reptilia 23: 105-108. Eco Evo. Koninklijke Brill NV. Web. 9 Dec. 2013.
  15. Hoff, Gerald (6 December 2012). Diseases of Amphibians and Reptiles. Springer Science & Business Media. pp. 643–. ISBN 978-1-4615-9391-1.
  16. Harvey, Michael B.; Ugueto, Gabriel N.; Gutberlet, Ronald L., Jr. (2012). "Review of Teiid Morphology with a Revised Taxonomy and Phylogeny of the Teiidae (Lepidosauria: Squamata)". Zootaxa 3459: 1–156.
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