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Quito Whorltail-Iguana (Stenocercus guentheri)
Reptiles of Ecuador | Sauria | Tropiduridae | Stenocercus | Stenocercus guentheri
English common names: Quito Whorltail-Iguana, Günther’s Whorltail Iguana.
Spanish common names: Guagsa de Quito, guagsa de Günther.
Recognition: ♂♂ 22.5 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=9.6 cm. ♀♀ 18.8 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=7.3 cm..1,2 The Quito Whorltail-Iguana (Stenocercus guentheri) differs from other lizards in its area of distribution (small, fossorial species in the genera Pholidobolus and Riama) by being larger and having keeled dorsal scales with pointed ends.3 The most similar whorltail-iguanas occurring nearby S. guentheri are S. angel and S. cadlei. However, these species occur north and south, respectively, of the known distribution of S. guentheri, and the males of these other lizards lack a black gular patch (patch present in most males of S. guentheri).4 The Quito Whorltail-Iguana can be differentiated from S. chota because males of the latter species lack a black gular patch and females have black blotches on the throat.2 Males of S. guentheri differ from females by being larger, more robust, and by generally having a more vivid color that includes a black throat patch.2

Figure 1: Individuals of Stenocercus guentheri from Tambopaxi Lodge, Cotopaxi pronvince (), and Tabacundo, Pichincha province (), Ecuador. sa=subadult.
Natural history: Locally extremely commonLikely to be seen every day, usually in large numbers.. Stenocercus guentheri inhabits dry and humid ecosystems in areas of evergreen montane forest, highland shrubland, and paramo. The species also occurs in human-modified environments such as rural gardens, plantations, pastures, and along roads.5,6 Quito Whorltail-Iguanas are diurnal and terrestrial. They forage on exposed soil, grass, and leaf-litter, and use stone walls, rocks, Agave plants, and shrubs less than 50 cm above the ground mainly for basking.5,7 These lizards are usually only active between 9:00 am and 3:30 pm during strongly sunny days,7 but they can also remain active during cloudy days.5,6 At night, individuals hide inside holes, crevices, or under rocks, but may also roost on shrubs or herbaceous vegetation up to 60 cm above the ground.7 Males occupy rocks and other elevated positions for basking and feeding while females tend to occupy the ground level.8 The diet of S. guentheri is composed primarily of arthropods, especially ants and beetles,9,10 but cannibalism has also been reported.9 Quito Whorltail-Iguanas are preyed upon by snakes (Erythrolamprus albiventris and Mastigodryas pulchriceps),11 the Andean Fox,12 and raptors such as the Carunculated Caracara (Phalcoboenus carunculatus)13 and hawks of the genus Parabuteo.7 When threatened, individuals seek refuge in holes, crevices, under rocks, or at the base of Agave and Stipa plants.8 If captured, they can bite or shed the tail.5 There is a record of a specimen with scoliosis, a malformation characterized by a sideways curvature of the spine.14 Stenocercus guentheri breeds throughout the year. Females lay clutches of two eggs per clutch2,8 and males defend territories by performing push-up displays and fighting with intruders.5
Conservation: Vulnerable Considered to be facing a high risk of extinction in the mid-term future..15 Stenocercus guentheri is listed in this category instead of Least Concern,16 because although it is a common species that tolerates a moderate degree of habitat disturbance, it meets IUCN Red List criteria17 to be included in the threatened category: the species’ extent of occurrence is estimated to be less than 5,000 km2, its habitat is severely fragmented, and there is continuing decline in the extent and quality of the ecosystems where it occurs. Based on maps of Ecuador’s vegetation cover published in 2012,18 no more than ~35% of the potential area of distribution of the species still holds native vegetation. Although S. guentheri is found in several protected areas (including Cotopaxi National Park, Cayambe-Coca National Park, Pululahua Geobotanical Reserve, Antisana Ecological Reserve, and Jerusalém Recreational Park), only 5.9% of the species’ total potential area of distribution is inside these areas. Since S. guentheri has a narrow thermal tolerance, it is expected that, as a result of rising ambient temperatures, 26.7% of populations will have a high risk of extinction by 2050.6
Distribution: Stenocercus guentheri is endemic to an estimated 4,266 km2 area in the inter-Andean valleys and paramos of northern Ecuador. The species has been recorded at elevations between 2098 and 4012 m (Fig. 2).

Figure 2: Distribution of Stenocercus guentheri in Ecuador. The star corresponds to the type locality: San Antonio de Pichincha. 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 (meaning “narrow”) and kerkos (meaning “tail”), refers to the laterally-compressed tail in some members of this genus, which contrasts with the dorsally flattened tail of other Tropiduridae.19 The specific epithet guentheri honors Albert Günther (1830–1914), a German-born British zoologist, ichthyologist, and herpetologist, best known for his role as Keeper of Zoology at the Natural History Museum in London.
See it in the wild: Quito Whorltail-Iguanas can be seen with almost complete certainty in protected areas such as Cotopaxi National Park and Pululahua Geobotanical Reserve. The lizards are most easily observed during sunny days along rock walls and living fences in semi-open areas nearby remnants of native vegetation.
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 Alejandro ArteagacAffiliation: Khamai Foundation, Quito, Ecuador.
How to cite? Quezada A (2021) Quito Whorltail-Iguana (Stenocercus guentheri). In: Arteaga A, Bustamante L, Vieira J, Guayasamin JM (Eds) Reptiles of Ecuador: Life in the middle of the world. Available from: www.reptilesofecuador.com. DOI: 10.47051/VIQX3499
Literature cited:
- 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
- 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
- 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.
- Torres-Carvajal O, Mafla-Endara P (2013) A new cryptic species of Stenocercus (Squamata: Iguanidae) from the Andes of Ecuador. Journal of Herpetology 47: 184–190. DOI: 10.1670/11-211
- Field notes, Reptiles of Ecuador book project.
- Guerra-Correa ES, Merino-Viteri A, Andrango MB, Torres-Carvajal O (2020) Thermal biology of two tropical lizards from the Ecuadorian Andes and their vulnerability to climate change. PLoS ONE 15: e0228043. DOI: 10.1371/journal.pone.0228043
- Ramírez-Jaramillo SM, Bejarano-Muñoz P, Rodríguez-Badillo M, Yánez-Muñoz M (2015) Uso de perchas nocturnas por Stenocercus guentheri (Iguanidae: Tropidurinae) en dos ecosistemas del distrito metropolitano de Quito (Ecuador). Boletín de la Asociación Herpetológica Española 26: 29–32.
- 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.
- Carvajal-Campos A (2009) Reproducción y dieta de la lagartija andina Stenocercus guentheri (Squamata: Iguania) en el Bosque Protector Jersualém. BSc thesis, Pontificia Universidad Católica del Ecuador, 97 pp.
- Photo by Juan Carlos Ríos.
- Cadena-Ortiz H, Barahona A, Bahamonde-Vinueza D, Brito J (2017) Anecdotal predation events of some snakes in Ecuador. Herpetozoa 30: 93–96.
- Reina Moreno DS (2019) Componentes alimentarios en la dieta del lobo de páramo Lycalopex culpaeus en la plataforma del aeropuerto Mariscal Sucre, parroquia Tababela, Cantón Quito, Pichincha, Ecuador. Avances en Ciencias e Ingeniería 11: 444–451. DOI: 10.18272/aci.v11i2.828
- de Vries T (2008) Historia natural del curiquingue (Phalcoboenus carunculatus) en los páramos del Antisana y Cotopaxi del Ecuador. Ediciones de la Universidad Católica, Quito, 83 pp.
- Ramírez-Jaramillo SM (2018) Primer reporte de cifoescoliosis en Stenocercus guentheri (Iguania: Tropiduridae), Andes Norte de Ecuador. Cuadernos de Herpetología 32: 55–57. DOI: 10.31017/CdH.2018.(2017-33)
- Reyes-Puig C (2015) Un método integrativo para evaluar el estado de conservación de las especies y su aplicación a los reptiles del Ecuador. MSc thesis, Pontificia Universidad Católica del Ecuador, 73 pp.
- Cisneros-Heredia DF, Yánez-Muñoz M, Brito J, Reyes-Puig C (2017) Stenocercus guentheri. The IUCN red list of threatened species. Available from: www.iucnredlist.org. DOI: 10.2305/IUCN.UK.2017-2.RLTS.T44579900A44579911.en
- IUCN (2001) IUCN Red List categories and criteria: Version 3.1. IUCN Species Survival Commission, Gland and Cambridge, 30 pp.
- MAE (2012) Línea base de deforestación del Ecuador continental. Ministerio del Ambiente del Ecuador, Quito, 30 pp.
- 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
Appendix 1: Locality data used to create the distribution map of Stenocercus guentheri in Ecuador (Fig. 2). Go to the section on symbols and abbreviations for a list of acronyms used. Asterisk (*) indicates type locality.
Country | Province | Locality | Source |
Ecuador | Cotopaxi | Cotopaxi National Park | iNaturalist |
Ecuador | Cotopaxi | Entrance to Cotopaxi National Park | iNaturalist |
Ecuador | Cotopaxi | Quebrada Agualongo | iNaturalist |
Ecuador | Cotopaxi | Tambopaxi Lodge | This work |
Ecuador | Cotopaxi | Volcán Rumiñahui | iNaturalist |
Ecuador | Imbabura | Atuntaqui | Torres-Carvajal 2007 |
Ecuador | Imbabura | Atuntaqui, 2 km NW of | iNaturalist |
Ecuador | Imbabura | Cerro Imbabura | iNaturalist |
Ecuador | Imbabura | Cotacachi | This work |
Ecuador | Imbabura | Cotacachi, 2.5 km W of | iNaturalist |
Ecuador | Imbabura | Hidroeléctrica Antigua | Ayerbe et al. 2007 |
Ecuador | Imbabura | Ibarra, 5 km S of | KU 134562 |
Ecuador | Imbabura | Ibarra, El Tejar | iNaturalist |
Ecuador | Imbabura | Ibarra, La Merced | MCZ R-8069 |
Ecuador | Imbabura | Laguna de Cuicocha | iNaturalist |
Ecuador | Imbabura | Lagunas de Mojanda | Torres-Carvajal 2007 |
Ecuador | Imbabura | Otavalo | KU 134555 |
Ecuador | Imbabura | Otavalo, 7.5 km N of | Torres-Carvajal 2007 |
Ecuador | Imbabura | San Juan de Ilumán, 2 km E of | iNaturalist |
Ecuador | Imbabura | San Pablo del Lago | Andrango et al. 2016 |
Ecuador | Imbabura | San Roque | iNaturalist |
Ecuador | Imbabura | Terreno familia Morales | This work |
Ecuador | Imbabura | Urcuquí, 6.8 km W of | iNaturalist |
Ecuador | Imbabura | Yachay Tech University | iNaturalist |
Ecuador | Imbabura | Zuleta | Guijarro Fuertes 2010 |
Ecuador | Napo | Laguna de la Mica, 2 km N of | iNaturalist |
Ecuador | Pichincha | Alangasí | iNaturalist |
Ecuador | Pichincha | Alangasí, 1.5 km S of | iNaturalist |
Ecuador | Pichincha | Bosque Protector Jerusalem | iNaturalist |
Ecuador | Pichincha | Bosque Protector Jerusalem, 2 km W of | Torres-Carvajal 2007 |
Ecuador | Pichincha | Calacalí | Guerra-Correa et al. 2020 |
Ecuador | Pichincha | Calacalí, 1 km NE of | iNaturalist |
Ecuador | Pichincha | Calacalí, 2.7 km NE of | iNaturalist |
Ecuador | Pichincha | Cangahua | MCZ R-80964 |
Ecuador | Pichincha | Casitagua | Andrango et al. 2016 |
Ecuador | Pichincha | Cayambe volcano slopes | Torres-Carvajal 2007 |
Ecuador | Pichincha | Cayambe, 7.7 km NW of | iNaturalist |
Ecuador | Pichincha | Central Hidroeléctrica Pasochoa | Ramírez-Jaramillo et al. 2015 |
Ecuador | Pichincha | Cerro Casitagua | iNaturalist |
Ecuador | Pichincha | Cerro La Marca, San Antonio de Pichincha | KU 134652 |
Ecuador | Pichincha | Ciudad Mitad del Mundo | iNaturalist |
Ecuador | Pichincha | Conocoto | MECN 4142 |
Ecuador | Pichincha | Conocoto, av. Ponce Enríquez | iNaturalist |
Ecuador | Pichincha | Cotopaxi Pungo | iNaturalist |
Ecuador | Pichincha | Cráter del Pulhulahua | iNaturalist |
Ecuador | Pichincha | Cuendina | Ramírez-Jaramillo et al. 2015 |
Ecuador | Pichincha | Cusubamba | PDOT Cusubamba 2015 |
Ecuador | Pichincha | Escuela Superior Militar Eloy Alfaro | Torres-Carvajal 2007 |
Ecuador | Pichincha | Granja Urkuwayku | iNaturalist |
Ecuador | Pichincha | Guayllabamba | MCZ R-8407 |
Ecuador | Pichincha | Guayllabamba, calle El Placer | MECN 4270 |
Ecuador | Pichincha | Guayllabamba, calle Ideyo | Torres-Carvajal 2007 |
Ecuador | Pichincha | Hacienda Criadora Miranda | MECN 464 |
Ecuador | Pichincha | Ilaló, northern slope | iNaturalist |
Ecuador | Pichincha | Ilaló, southern slope | iNaturalist |
Ecuador | Pichincha | Laguna de Limpiopungo | iNaturalist |
Ecuador | Pichincha | Lloa | Torres-Carvajal 2007 |
Ecuador | Pichincha | Machachi | MCZ R-8420 |
Ecuador | Pichincha | Machachi, planta de Tesalia | Torres-Carvajal 2007 |
Ecuador | Pichincha | Mirador del Isco | This work |
Ecuador | Pichincha | Mirador del Pulhulahua | iNaturalist |
Ecuador | Pichincha | Molinuco Ecological Refuge | iNaturalist |
Ecuador | Pichincha | Monumento Mitad del Mundo | CAS 152053 |
Ecuador | Pichincha | Nono, 1.75 km W of | This work |
Ecuador | Pichincha | Nono, 4 km N of | iNaturalist |
Ecuador | Pichincha | Olmedo, 8 km NE of | iNaturalist |
Ecuador | Pichincha | Parque Arqueológico Rumipamba | iNaturalist |
Ecuador | Pichincha | Parque de Guápulo | Photo by Lorena Benítez |
Ecuador | Pichincha | Parque Itchimbía | iNaturalist |
Ecuador | Pichincha | Pasochoa Volcano Forest | MCZ R-175060 |
Ecuador | Pichincha | Pifo | This work |
Ecuador | Pichincha | Pintag–Antisana road | Torres-Carvajal 2007 |
Ecuador | Pichincha | Pintag, 2 km S of | iNaturalist |
Ecuador | Pichincha | Pucará de Rumicucho | iNaturalist |
Ecuador | Pichincha | Puembo | MCZ R-164422 |
Ecuador | Pichincha | Pululahua Geobotanical Reserve 1 | iNaturalist |
Ecuador | Pichincha | Pululahua Geobotanical Reserve 2 | iNaturalist |
Ecuador | Pichincha | Pululahua, 6.1 km NW of | iNaturalist |
Ecuador | Pichincha | Quito, Bellavista | iNaturalist |
Ecuador | Pichincha | Quito, Calderón | iNaturalist |
Ecuador | Pichincha | Quito, calle Jorge Juan | Torres-Carvajal 2007 |
Ecuador | Pichincha | Quito, Carcelén | iNaturalist |
Ecuador | Pichincha | Quito, Guápulo | iNaturalist |
Ecuador | Pichincha | Quito, La Tola | iNaturalist |
Ecuador | Pichincha | Quito, Parque La Carolina | iNaturalist |
Ecuador | Pichincha | Quito, Parque Metropolitano del Sur | iNaturalist |
Ecuador | Pichincha | Quito, San Miguel de Amagasi | iNaturalist |
Ecuador | Pichincha | Quito, San Vicente | iNaturalist |
Ecuador | Pichincha | Quito, Tréboles del Sur | iNaturalist |
Ecuador | Pichincha | Quito, valle Valparaíso | USNM 201235 |
Ecuador | Pichincha | Reserva Chakana | iNaturalist |
Ecuador | Pichincha | Río Chiche, 3.5 km E of | KU 152172 |
Ecuador | Pichincha | San Antonio de Pichincha, calle Moraspungo | iNaturalist |
Ecuador | Pichincha | San Antonio de Pichincha, Caspigasi | iNaturalist |
Ecuador | Pichincha | San Antonio de Pichincha* | Fritts 1974 |
Ecuador | Pichincha | San Rafael, Los Cedros | iNaturalist |
Ecuador | Pichincha | Santa Marianita de Pingulmi | LACM 58808 |
Ecuador | Pichincha | Santa Rosais Farm | MCZ R-8435 |
Ecuador | Pichincha | Slopes of Cotopaxi volcano | This work |
Ecuador | Pichincha | Tababela | Ramírez-Jaramillo et al. 2015 |
Ecuador | Pichincha | Tababela, Aeropuerto | Cadena-Ortiz et al. 2017 |
Ecuador | Pichincha | Tabacundo, 4.8 km N of | This work |
Ecuador | Pichincha | Tanlahua | iNaturalist |
Ecuador | Pichincha | Tumbaco | iNaturalist |
Ecuador | Pichincha | Uyumbicho | Torres-Carvajal 2007 |
Ecuador | Pichincha | Valle de los Chillos, Calle Río Pastaza | MECN 504 |
Ecuador | Pichincha | Yaruquí, 2 km E of | iNaturalist |