Published May 17, 2022. Open access.

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Amazon Toad-headed Turtle (Mesoclemmys raniceps)

Reptiles of Ecuador | Testudines | Chelidae | Mesoclemmys raniceps

English common name: Amazon Toad-headed Turtle.

Spanish common names: Tortuga cabeza de sapo, cabezón, huele feo.

Recognition: ♂♂ 33.4 cmMaximum straight length of the carapace. ♀♀ 37.2 cmMaximum straight length of the carapace..1,2 The Amazon Toad-headed Turtle (Mesoclemmys raniceps) can be identified from other Amazonian freshwater turtles by having a laterally retracting neck, a conspicuously wide head covered by small scales, and a broad smooth carapace.3 In Amazonian Ecuador, M. raniceps is most likely to be confused with M. gibba, from which it differs by having a broader (greater than 23% of carapace length) head with wide areas of light pigmentation.4,5 It may also be confused with Phrynops geoffroanus, a turtle characterized by having a narrower head with a distinct black postocular stripe.3,6 Turtles of the genus Podocnemis differ from those of the genus Mesoclemmys by having the dorsum of the head covered by large broad scales.3 Juveniles of the Amazon Toad-headed Turtle have a black head with or without broad yellow dorsolateral bands, but these markings become faint after 6–8 years.25,7 Males of this species are smaller than females and have longer and thicker tails.4

Figure showing variation among individuals of Mesoclemmys raniceps

Figure 1: Individuals of Mesoclemmys raniceps from Anguilla, Loreto department, Perú. j=juvenile.

Natural history: RareTotal average number of reported observations per locality less than ten. and often overlooked due to the species’ bottom-dwelling habits and preference for pristine habitats.810 Mesoclemmys raniceps is an aquatic turtle that inhabits slow-moving bodies of water in well-preserved lowland rainforests.10 Amazon Toad-headed Turtles are nocturnal2 and spend almost the entirety of their life in streams, rivers, lagoons, temporary ponds,7 oxbow lakes, drainage ditches,11 marshes and swamps.3,10,12 Occasionally, individuals may be seen crossing forest trails.13 During the rainy season, these turtles dwell further inland when large Amazonian rivers overflow the forest.3 The diet in this species is composed primarily (~70%) on gastropod mollusks,14 but also includes fish, frogs, tadpoles, earthworms, insects, crustaceans, and fruits.2,3,14 When threatened, individuals of M. raniceps produce a fetid smell; hence the local name tortuga hedionda (=stinking turtle) in Spanish.2,3 In Brazil, the breeding season in this species takes place between May and August.4 Females lay clutches of 2–11 (usually 4–7) eggs that measure 39.8􏰀–43.6 x 29.6􏰀–37.0 mm and weigh 26.5􏰀–35.9 g.4,7 These are laid in embankments of streams and watercourses3 and hatch after an incubation period of 211–249 days (~7–8 months).4 Hatchlings measure 49.2–60.1 mm in straight carapace length.4 In captivity, one individual lived for at least 19 years.15

Conservation: Least Concern Believed to be safe from extinction given current circumstances.. Mesoclemmys raniceps has not been formally included in any IUCN Red List category.1 Here, it is proposed to be assigned to the LC category given its wide distribution throughout the Amazon basin, especially over areas that have not been heavily affected by deforestation. Therefore, the species is considered to be facing no major immediate extinction threats. Adults of M. raniceps are under no widespread pressure from harvesting, probably due to their rarity and undesirable smell.2,3 Juveniles, though beautifully colored, are not common in the international trade of exotic species.3 However, it seems like M. raniceps requires pristine forests to survive; thus, some populations might be declining due to habitat loss and degradation.10

Distribution: Mesoclemmys raniceps is native to an estimated 3,547,705 km2 area in the Amazon basin of Bolivia, Brazil, Colombia, Ecuador, Perú, and Venezuela.1,10 In Ecuador, the species has been recorded at elevations between 150 and 348 m (Fig. 2).

Distribution of Mesoclemmys raniceps in Ecuador

Figure 2: Distribution of Mesoclemmys raniceps in Ecuador. See Appendix 1 for a complete list of the presence localities included in the map.

Etymology: The generic name Mesoclemmys comes from the Greek words mesos (meaning “middle”) and klemmys (meaning “tortoise”).16 At the time of description,17 turtles of this genus were believed to be an intermediate form between Hydraspis and Platemys.18 The specific epithet raniceps, which comes from the Latin words rana (meaning “frog”) and ceps (meaning “head”),16 refers to the strikingly broad head in this turtle.

See it in the wild: Amazon Toad-headed Turtles are rarely encountered in the wild in Ecuador. Most recent observations come from black-water streams and marshes in Cuyabeno Reserve and Tiputini Biodiversity Station. In these areas, the turtles are most easily found by walking along slow-moving bodies of water right after sunset or by setting up baited fyke nets, funnel traps, and fishing nets.3,4,10

Acknowledgments: Special thanks to Jiří Moravec for providing access to the individuals of Mesoclemmys raniceps photographed in this account.

Author and photographer: Alejandro ArteagaaAffiliation: Biodiversity Field Lab, Khamai Foundation, Quito, Ecuador.

How to cite? Arteaga A (2022) Amazon Toad-headed Turtle (Mesoclemmys raniceps). In: Arteaga A, Bustamante L, Vieira J, Guayasamin JM (Eds) Reptiles of Ecuador: Life in the middle of the world. Available from: DOI: 10.47051/GIPG4789

Literature cited:

  1. Rhodin AGJ, Iverson JB, Bour R, Fritz U, Georges A, Shaffer HB, van Dijk PP (2021) Turtles of the world: annotated checklist and atlas of taxonomy, synonymy, distribution, and conservation status. Chelonian Research Monographs 8: 1–472. DOI: 10.3854/crm.8.checklist.atlas.v9.2021
  2. Ferrara CR, Fagundes CK, Morcatty TQ, Vogt RC (2017) Quelônios Amazônicos: guia de identificação e distribuição. Wildlife Conservation Society, Manaus, 180 pp.
  3. Rueda-Almonacid JV, Carr JL, Mittermeier RA, Rodríguez-Mahecha JV, Mast RB, Vogt RC, Rhodin AGJ, de la Ossa-Velásquez J, Rueda JN, Mittermeier CG (2007) Las tortugas y los cocodrilianos de los países andinos del trópico. Conservación Internacional, Bogotá, 538 pp.
  4. Cunha FAG, Fernandes T, Franco J, Vogt RC (2019) Reproductive biology and hatchling morphology of the Amazon Toad-headed Turtle (Mesoclemmys raniceps) (Testudines: Chelidae), with notes on species morphology and taxonomy of the Mesoclemmys group. Chelonian Conservation and Biology 18: 1–16. DOI: 10.2744/CCB-1271.1
  5. Molina FB, Machado FA, Zaher H (2012) Taxonomic validity of Mesoclemmys heliostemma (McCord, Joseph-Ouni & Lamar, 2001) (Testudines, Chelidae) inferred from morphological analysis. Zootaxa 3575: 63–77. DOI: 10.11646/zootaxa.3575.1.4
  6. Duellman WE (1978) The biology of an equatorial herpetofauna in Amazonian Ecuador. Publications of the Museum of Natural History, University of Kansas 65: 1–352.
  7. Moravec J (2017) First data on reproduction and hatchling morphology of Mesoclemmys heliostemma (McCord, Joseph-Ouni & Lamar, 2001). Herpetozoa 29: 205–208.
  8. Morcatty TQ (2015) Mesoclemmys raniceps (Black-lined Toad-headed Turtle): geographic distribution. Herpetological Review 46: 382.
  9. Field notes, Reptiles of Ecuador book project.
  10. Brito ES, Valadão RM, Cunha FAG, Gomes de Araújo C, Viana PF, Fernandes Médice I (2019) New records of Mesoclemmys raniceps (Testudines, Chelidae) for the states of Amazonas, Pará and Rondônia, North Brazil, including the Tocantins basin. Herpetology Notes 12: 283–289.
  11. Balensiefer DC, Vogt RC (2012) Mesoclemmys raniceps (Amazon Toad-headed Turtle): geographic distribution. Herpetological Review 43: 303.
  12. Cisneros-Heredia DF (2006) Turtles of the Tiputini Biodiversity Station with remarks on the diversity and distribution of the Testudines from Ecuador. Biota Neotropica 6: 1–16. DOI: 10.1590/S1676-06032006000100011
  13. Dixon JR, Soini P (1986) The reptiles of the upper Amazon Basin, Iquitos region, Peru. Milwaukee Public Museum, Milwaukee, 154 pp.
  14. Fachin Teran A, Vogt RC, Gomez MFS (1995) Food habits of an assemblage of turtles in the rio Guapore, Rondonia, Brazil. Journal of Herpetology 29: 536–547.
  15. Jiří Moravec, pers. comm.
  16. Brown RW (1956) Composition of scientific words. Smithsonian Books, Washington D.C., 882 pp.
  17. Gray JE (1873) Observations on chelonians, with descriptions of new genera and species. Annals and Magazine of Natural History 11: 289–308.
  18. Uetz P, Freed P, Hošek J (2021) The reptile database. Available from:

Appendix 1: Locality data used to create the distribution map of Mesoclemmys raniceps in Ecuador (Fig. 2). Go to the section on symbols and abbreviations for a list of acronyms used.

EcuadorOrellanaSendero PumañambiTorres-Carvajal et al. 2019
EcuadorOrellanaTiputini Biodiversity Station Cisneros-Heredia 2006
EcuadorPastazaJuyuintzaOrtega-Andrade 2010
EcuadorPastazaKurintzaOrtega-Andrade 2010
EcuadorPastazaMouth of Río PindoMCZ 153154
EcuadorSucumbíosMouth of Río CuyabenoMcCord et al. 2001
EcuadorSucumbíosRío CuyabenoiNaturalist
EcuadorSucumbíosShushufindiCisneros-Heredia 2006
PerúLoretoAnguillaMoravec 2017
PerúLoretoZona Reservada PucacuroMolina et al. 2012
PerúLoretoCampamento AndoasRhodin et al. 2021
PerúLoretoRío PutumayoRhodin et al. 2021