Published August 9, 2021. Updated January 29, 2024. Open access.

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Red-Black Whorltail-Iguana (Stenocercus rhodomelas)

Reptiles of Ecuador | Sauria | Tropiduridae | Stenocercus rhodomelas

English common name: Red-Black Whorltail-Iguana.

Spanish common name: Guagsa ventrirroja.

Recognition: ♂♂ 23.5 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=9.3 cm. ♀♀ 23.6 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=7.3 cm..1,2 Stenocercus rhodomelas differs from other lizards in the valley of the Río Jubones by being larger and having keeled dorsal scales with pointed ends.3 This species can be differentiated from S. festae by having a black V-shaped dorsal stripe between the shoulders and a black-pink pattern on the belly in males (Fig. 1). Another similar species is S. ornatus, which lacks an extensive black patch on the gular region in adult males.2 Stenocercus rhodomelas is easily differentiated from S. simonsii by lacking a strongly spiny tail.2 Males of S. rhodomelas differ from females by having a black throat patch, a wide mid-ventral black patch, and pink belly margins (patter absent in females).2,4

Figure showing variation among individuals of Stenocercus rhodomelas

Figure 1: Individuals of Stenocercus rhodomelas from Azuay province, Ecuador: Oña (); Poetate (); Yunguilla (). j=juvenile.

Natural history: Stenocercus rhodomelas is a diurnal and terrestrial lizard that inhabits the dry highland shrubland ecosystem.1,5 The species occurs in secondary vegetation, open areas dominated by grasses and shrubs,2 and desert areas along roads.6 Red-Black Whorltail-Iguanas need prolonged periods of direct sunlight to become active. They bask on large rocks, stone walls, at the base of cacti, or on the sand during hot sunny hours.6,7 The only known predator of this species is the Burrowing Owl (Athene cunicularia).8 Males defend their territories by performing push-up displays and fighting with other males.6 If threatened, these lizards usually flee into the vegetation; if captured, they may shed the tail and bite.6

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Conservation: Endangered Considered to be facing a high risk of extinction in the near future.. Stenocercus rhodomelas is proposed to be included in this category, instead of Vulnerable,9 because the species’ extent of occurrence is very small (estimated to be around 1,133 km2) and its habitat is under pressure due to increased human activities such as infrastructure expansion, agriculture, and livestock grazing.9 Burning and mining are also a prevalent threat in the region.9 Based on maps of Ecuador’s vegetation cover published in 2012,10 an estimated ~57% of the native habitat of S. rhodomelas has already been destroyed. Where these lizards are abundant, they are killed by people9 or preyed upon by domestic animals such as cats and chickens.6 Additionally, most populations are outside protected areas, except for those in the Yunguilla Biological Reserve.

Distribution: Stenocercus rhodomelas is endemic to an area of approximately 1,133 km2 in the xeric inter-Andean valley of the Río Jubones in southern Ecuador (Fig. 2).

Distribution of Stenocercus rhodomelas in Ecuador

Figure 2: Distribution of Stenocercus rhodomelas in Ecuador. The star corresponds to the type locality: Oña, Azuay province. See Appendix 1 for a complete list of the presence localities included in the map.

Etymology: The generic name Stenocercus, which comes from the Greek words stenos (=narrow) and kerkos (=tail), refers to the laterally-compressed tail in some members of this genus, which contrasts with the dorsally flattened tail of other Tropiduridae.11 The specific epithet rhodomelas comes from the Greek words rhodo (=pink) and melas (=black),12 and refers to the ventral coloration of the males.

See it in the wild: Red-Black Whorltail-Iguanas can be seen with almost complete certainty during strongly sunny days at specific desert sites in the valley of the Río Jubones. The best time to look for these lizards is during the first hours after sunrise or just before sunset, when individuals are easier to approach.

Author: Amanda QuezadaaAffiliation: Tropical Herping (TH), Quito, Ecuador.,bAffiliation: Laboratorio de Herpetología, Universidad del Azuay, Cuenca, Ecuador.

Editor: Alejandro ArteagacAffiliation: Khamai Foundation, Quito, Ecuador.

Photographers: Jose VieiraaAffiliation: Tropical Herping (TH), Quito, Ecuador.,dAffiliation: ExSitu, Quito, Ecuador. and Frank PichardoaAffiliation: Tropical Herping (TH), Quito, Ecuador.

How to cite? Quezada A (2024) Red-Black Whorltail-Iguana (Stenocercus rhodomelas). In: Arteaga A, Bustamante L, Vieira J (Eds) Reptiles of Ecuador: Life in the middle of the world. Available from: DOI: 10.47051/CAKV5435

Literature cited:

  1. Torres-Carvajal O (2000) Ecuadorian lizards of the genus Stenocercus (Squamata: Tropiduridae). Scientific Papers Natural History Museum, The University of Kansas 15: 1–38. DOI: 10.5962/bhl.title.16286
  2. Torres-Carvajal O (2007) A taxonomic revision of South American Stenocercus (Squamata: iguania) lizards. Herpetological Monographs 21: 76–178. DOI: 10.1655/06-001.1
  3. Peters JA, Donoso-Barros R (1970) Catalogue of the Neotropical Squamata: part II, lizards and amphisbaenians. Bulletin of the United States National Museum, Washington, D.C., 293 pp.
  4. Boulenger GA (1899) Descriptions of new reptiles and batrachians collected by Mr. P.O. Simons in the Andes of Ecuador. Annals and Magazine of Natural History 7: 454–457.
  5. Torres-Carvajal O, Pazmiño-Otamendi G, Salazar-Valenzuela D (2019) Reptiles of Ecuador: a resource-rich online portal, with dynamic checklists and photographic guides. Amphibian & Reptile Conservation 13: 209–229.
  6. Field notes, Reptiles of Ecuador book project.
  7. Fritts TH (1974) A multivariate and evolutionary analysis of the Andean iguanid lizards of the genus Stenocercus. Memoirs of the San Diego Society of Natural History 7: 1–89.
  8. Cadena-Ortíz H, Garzón C, Villamarín-Cortéz S, Pozo-Zamora GM, Echeverría-Vaca G, Yánez J, Brito J (2016) Diet of the Burrowing Owl Athene cunicularia, in two locations of the inter-Andean valley Ecuador. Revista Brasileira de Ornitologia 24: 122–128. DOI: 10.1007/BF03544340
  9. Cisneros-Heredia DF (2019) Stenocercus rhodomelas. The IUCN Red List of threatened species. Available from: DOI: 10.2305/IUCN.UK.2019-3.RLTS.T50950708A50950717.en
  10. MAE (2012) Línea base de deforestación del Ecuador continental. Ministerio del Ambiente del Ecuador, Quito, 30 pp.
  11. Duméril AMC, Bibron G (1837) Erpétologie générale ou Histoire Naturelle complète des Reptiles. Librairie Encyclopédique de Roret, Paris, 571 pp. doi:10.5962/bhl.title.45973
  12. Brown RW (1956) Composition of scientific words. Smithsonian Books, Washington D.C., 882 pp.

Appendix 1: Locality data used to create the distribution map of Stenocercus rhodomelas in Ecuador (Fig. 2). Go to the section on symbols and abbreviations for a list of acronyms used. Asterisk (*) indicates type locality.

EcuadorAzuay5 km vía Nabón-San IsidroTorres-Carvajal 2007
EcuadorAzuayAbdón CalderonTorres-Carvajal 2007
EcuadorAzuayBuenos Aires, 11.8 km N ofTorres-Carvajal 2007
EcuadorAzuayCataviñaTorres-Carvajal 2007
EcuadorAzuayCuenca–Machala roadTorres-Carvajal 2007
EcuadorAzuayGirónTorres-Carvajal 2007
EcuadorAzuayGirón, 12 km SW ofTorres-Carvajal 2007
EcuadorAzuayGirón, 7–8 km W ofTorres-Carvajal 2007
EcuadorAzuayJubones, 2.5 km NE ofiNaturalist; photo examined
EcuadorAzuayLa UniónReptiles of Ecuador book database
EcuadorAzuayMine near Río RircayReptiles of Ecuador book database
EcuadorAzuayOña*Boulenger 1899
EcuadorAzuayOña, 2 km N ofTorres-Carvajal 2007
EcuadorAzuayOña, 2 km S ofReptiles of Ecuador book database
EcuadorAzuayPoetateThis work; Fig. 1
EcuadorAzuayRío JubonesReptiles of Ecuador book database
EcuadorAzuayRío MinasTorres-Carvajal 2007
EcuadorAzuayRoad to PasajeTorres-Carvajal 2007
EcuadorAzuaySan Sebastián de Yuluc, 6 km E ofTorres-Carvajal et al. 2019
EcuadorAzuaySanta IsabelTorres-Carvajal 2007
EcuadorAzuaySanta Isabel, 1.4 km NE ofReptiles of Ecuador book database
EcuadorAzuaySanta Isabel, 11 km W ofTorres-Carvajal 2007
EcuadorAzuaySulupali GrandeiNaturalist; photo examined
EcuadorAzuaySusudel–Poetate roadReptiles of Ecuador book database
EcuadorAzuayValle de YunguillaTorres-Carvajal 2007
EcuadorAzuayVía a Laguna de ZhograJosé Manuel Falcón, pers. comm.
EcuadorAzuayYunguillaThis work; Fig. 1
EcuadorAzuayYunguilla Biological ReserveYánez-Muñoz 2010
EcuadorAzuayYunguillapambaTorres-Carvajal 2007
EcuadorEl OroAbañínPhoto by Sebastián Valverde
EcuadorLojaChamical, 800 m W ofTorres-Carvajal et al. 2019
EcuadorLojaPiedra LabradaCadena-Ortíz et al. 2016
EcuadorLojaSan JoséTorres-Carvajal 2007
EcuadorLojaSan Sebastián de Yuluc, 9 km E ofiNaturalist; photo examined
EcuadorLojaSumaipamba, 5 km S ofiNaturalist; photo examined
EcuadorLojaSumaipamba, 6 km S ofiNaturalist; photo examined
EcuadorLojaVía Güeledel–ChamicalTorres-Carvajal et al. 2019