I came across quite a few tegus – large lizards – when visiting Iguazu National Park in northern Argentina. As far as I can tell, they are all the Argentine black and white tegu (Salvator merianae), also called the Argentine giant tegu (1). They wander round quite happily, despite the presence of large numbers of people coming to see the waterfalls.

Tegus seem to eat just about everything! That is why are called omnivores: omni means ‘all’ or ‘every’. They will apparently consume invertebrates (millipedes, arachnids, insects and molluscs), vertebrates (birds, fishes, amphibians, lizards and small mammals), bird and turtle eggs, fruits, carrion and mushrooms (2). It’s not surprising given this diet that they grow so large! Over four feet long.

Tegus look a lot like monitor lizards (an Old World group) but they are not closely related, so must be assumed to have evolved to fill a similar niche (convergent evolution). There are 7 species of tegus, which were originally placed in a single genus, Tupinambis. But tegu taxonomy seems to have gone through some changes recently and the Argentine black and white, or giant tegu, was recently reclassified as Salvator merianae (3). For the record, the genus Salvator now consists of three species: S. duseni (The Yellow tegu), S. merianae and S. rufescens (The Red tegu), which mainly occur in open ecosystems (4). The genus Tupinambis now contains four species: T. longilineus (The Rondonia tegu), T. palustris (The Swamp tegu), T. quadrilineatus (The Striped or Four-lined tegu) and T. teguixin (The Golden tegu); and these tegus are mainly to be found in forest ecosystems (4).

Some of the tegus I photographed, like the individuals shown above and below, had a more yellow or golden colour and I wondered if these could have been Golden tegus (Tupinambis teguixin). Tegus are separated on the basis of a large number of characters, one of which is the number of loreal scales they have (3, 4). These are the large scales between the eyes and nostrils. All of the individuals shown here seem to have two large scales, so they cannot be T. teguixin, as that species only has one large loreal scale (4).

Surprisingly, tegus make good pets! Apparently, they are quite docile and can be house trained; they also get quite attached to their owners and get aggressive if they are not handled regularly! (1, 2). There are a number of Facebook sites (e.g. ‘The Tegu-phile’ and ‘Tegus from Around the World’) for people who love tegus! Unfortunately, not everyone appreciates their good nature and many are hunted for food and skins (5). Despite this fact, their numbers seem to be holding up.

There were also some very nice waterfalls as well as lizards!

1. http://www.inaturalist.org/taxa/318758-Salvator-merianae
2. http://carnivoraforum.com/topic/9508642/1/
3. Harvey, M.B., G.N. Ugueto and R.L. Gutberlet Jr. 2012. Review of Teiid Morphology with a Revised Taxonomy and Phylogeny of the Teiidae (Lepidosauria: Squamata). Zootaxa 3459: 1-156.
4. Passos, D. C., Lima-Araujo, F., Melo, A. C. B., & Borges-Nojosa, D. M. (2013). New state record and distribution extension of the golden tegu Tupinambis teguixin (Linnaeus, 1758)(Squamata: Teiidae) to the Caatinga biome, northeastern Brazil. Check List, 9(6), 1524-1526.
5. Embert, D., Fitzgerald, L. & Waldez, F. 2010. Salvator merianae. The IUCN Red List of Threatened Species 2010:e.T178340A7526681. http://www.iucnredlist.org/details/178340/0