Description
Telmatobius culeus is a large, completely aquatic frog (74.82 mm to 137.95 mm SVL). This frog has a large flat head with a round snout, a thick, well-developed dorsal disc, and prominent skin folds (Benavides et al. 2002). Lungs are greatly reduced and are less than one-third the size that would be expected for a ranid frog of the same body size (Allen 1922). T. culeus respires primarily through its skin and has many large vascularized skin folds on the dorsum, sides and hind limbs as well as a highly vascularized buccal cavity (Macedo 1960). The skin folds essentially serve as gills for these animals (Hutchison et al. 1976).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Bolivia, Peru

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (9 records).

T. culeus is distributed in a region that spans the border between Bolivia and Peru. It is found within Lake Titicaca and in rivers flowing into the lake, as well as in small ponds about 70 km away, near Lago Saracocha (Benavides et al. 2002). In addition, a single specimen has been reported from a lower-elevation locality (2,500 m asl) about 200 km east of Lake Titicaca, in warm springs near the Rio Yura (Benavides et al. 2002).

The elevation of Lake Titicaca is 3,812 m and it reaches a maximum depth of 281 m (Hutchison et al. 1976). Water temperature average is 10°C at both the surface and the bottom; surface waters fluctuate slightly but the annual fluctuation is less than 4°C (Hutchison et al. 1976). The water is saturated with oxygen because of the high winds and wave action (Hutchison et al. 1976).

Life History, Abundance, Activity, and Special Behaviors
This frog is fully aquatic (Allen 1922). Although it seems to prefer the bottom of the lake, it occurs throughout the water column and has been observed on rock ledges within two feet of the water surface (Hutchison et al. 1976). It does not surface for air if the water is well-oxygenated, although dissections have shown small amounts of gas in the lungs (Hutchison et al. 1976). T. culeus is able to effectively remove oxygen from water with its skin (Hutchison et al. 1976). Lungs are reduced and poorly vascularized; respiration appears to take place primarily through the large and highly vascularized skin folds hanging from the dorsum, sides and hind limbs (Macedo 1960). Other adaptations for aquatic life at high altitude include one of the highest red blood cell (RBC) counts reported for any anuran (see Ruiz et al. 1983 for a comparison), one of the smallest red blood cell volumes reported for any anuran (see Ruiz et al. 1983 for comparisons between species), a relatively high oxygen capacity, and a relatively high hemoglobin content (Hutchison et al. 1976). Under hypoxic conditions, the frog will surface; if it is prevented from surfacing, it does not struggle but stands on the bottom with legs and toes extended to maximize skin surface exposure to the water, and will bob up and down about once every six seconds (Hutchison et al. 1976). This acts to move the large skin flaps, which breaks up the boundary layer between the skin and the water, allowing the skin to more fully absorb the limited oxygen from the water (Hutchison et al. 1976).

This species has the lowest reported metabolic rate (14.1 microliters/gram-hour) under non-hypoxic conditions for any frog, and one of the lowest among all amphibians; only a few salamander genera have lower metabolic rates (Hutchison et al. 1976). This rate is likely to be an overestimate, as it was measured at low altitude in captive frogs and not at the elevation of the natural habitat in Lake Titicaca (Hutchison et al. 1976). An extremely low metabolic rate is likely to be the case for other species in the genus Telmatobius as well (see Ruiz et al. 1983).

Breeding takes place near the shoreline in shallow waters (Stuart et al. 2008). The clutch size is about 500 eggs (Pérez 1996).

Under the stress of being held, T. culeus secretes copious quantities of a sticky, milky secretion; Allen (1922) reports that the skin creases "become filled with it."

Diet includes amphipods, snails, aquatic insects, tadpoles, and fish; stomach contents of one T. culeus were found to include a four-inch-long fish of the genus Orestias (Allen 1922).

Trends and Threats
It was once common, but due to massive population declines (more than 80% over the past fifteen years), Telmatobius culeus is now critically endangered (Benavides et al. 2002). Captive-breeding programs have so far not been successful (Perez Bejar 2005). Although its habitat lies within the Lake Titicaca Reserve, threats include overcollection, introduced trout, lake water extraction, water pollution, and loss of breeding habitat (Stuart et al. 2008). It is not known whether T. culeus is susceptible to chytridiomycosis, but this disease also presents a potential threat (Stuart et al. 2008); it has been speculated that all three Ecuadorian species of Telmatobius have been extirpated by chytridiomycosis (Merino-Viteri et al. 2005), and chytrid infections of Peruvian T. marmoratus have been reported (Seimon et al. 2005; Seimon et al. 2007), as well as Argentinian T. pisanoi (Barrionuevo and Ponssa 2008). Telmatobius species share traits common to amphibian species with higher susceptibility to chytridiomycosis: high altitude distributions, low fecundity, strongly aquatic, and specialized habitat (Barrionuevo and Ponssa 2008).

Relation to Humans
At one time it was thought the frog's thick, sticky white secretion, which is exuded under stress, may render it unpalatable (Hutchison et al. 1976). Currently, one of the reasons for overharvesting of adults of T. culeus is for consuming as an aphrodisiac, especially on the Peruvian side of the lake (A. Catenazzi, pers.comm.).

Possible reasons for amphibian decline

General habitat alteration and loss
Drainage of habitat
Dams changing river flow and/or covering habitat
Local pesticides, fertilizers, and pollutants
Long-distance pesticides, toxins, and pollutants
Predators (natural or introduced)
Introduced competitors
Intentional mortality (over-harvesting, pet trade or collecting)
Climate change, increased UVB or increased sensitivity to it, etc.

Comments
This species was first described by Garman (1876). See Benavides et al. (2002) for a discussion of species boundaries among Lake Titicaca species of Telmatobius, using allozyme data and multivariate morphometrics; there are different morphs along a depth gradient (similar to the situation in some freshwater fish species) but all are now considered T. culeus. Sinsch et al. (1995), using multivariate morphometric assessments, had previously concluded that a number of purported subspecies were all junior synonyms of T. culeus. See also Benavides (2005); this study was not able to distinguish between T. culeus and T. marmoratus from the Lake Titicaca drainage, using mtDNA.

This species was featured as News of the Week on 13 February 2017:

Things are looking up for the Titicaca water frog, Telmatobius culeus, also known as the “scrotum frog.” In January 2017, Peruvian President Pedro Pablo Kuczynski announced that the government will build ten water treatment plants around Lake Titicaca, the largest freshwater lake in South America. For decades, the lake has experienced high levels of water contamination resulting from mining activities, agricultural runoff, and raw sewage flowing into the lake—threatening local wildlife and people. Categorized as Critically Endangered by the IUCN Red List of Threatened Species, T. culeus is an iconic species because of remarkable adaptations to aquatic life at high elevation. The species was recently included in Appendix I of CITES, the Convention of International Trade in Endangered Species of Wild Fauna and Flora, in a measure to curtail its illegal collection and trade. News about construction of water treatment plants was equally well received by locals and the conservation community, especially after massive die-offs of the frog were reported from various sites around the lake (Written by Rudy von May).

This species was featured as News of the Week on 11 November 2024:

One of the primary challenges of life at high elevation is environmental hypoxia – a reduction in available oxygen necessary for gas exchange (e.g., breathing). Like mountain climbers attempting to summit Mt. Everest with supplemental oxygen, animals also experience and suffer from acute hypoxia at high elevations. Numerous studies describe adaptive changes in proteins like hemoglobin to compensate for reduced O2 availability at high altitude. Although one might imagine that high-elevation lakes are somehow buffered from hypoxia, this is not actually the case and animals living in such low oxygen lakes also require compensatory adaptions. One of the world’s most remarkable frogs is the Lake Titicaca frog (Telmatobius culeus). This permanently aquatic frog occurs in the world’s highest navigable lake (Lake Titicaca) at an elevation of 3812 m (12,507 feet) in the Andes Mountains. Its highly vascularized skin hangs in folds on its body, increasing the surface area for cutaneous gas exchange. Padava et al. (2024) provide further experimental evidence of adaptation, specifically a derived behavioral response to particularly acute hypoxic conditions that these frogs periodically experience (especially at greater depths in the lake where O2 concentrations are extremely low). During these events, the frogs initially become motionless, but as oxygen concentrations fall below 50% of atmospheric oxygen conditions (which are already very low at 3812 m elevation!), they engage in push-up like behaviors that apparently increase cutaneous gas exchange by billowing their loose skin and possibly breaking up low-O2 boundary layers that form around their skin folds. Lake Titicaca frogs are famous for living at high elevation and having a peculiar morphology that permits a fully aquatic lifestyle. And now we can appreciate them for being highly specialized denizens of super hypoxic environments, no less spectacular than, for example, Bar-headed Geese that migrate annually over the Himalayas. (Written by Jim McGuire)

References

Allen, W. R. (1922). ''Notes on the Andean Frog, Telmatobius culeus (Garman).'' Copeia, (108), 52-54.

Barrionuevo, J. S., and Ponssa, M. L. (2008). ''Decline of three species of the genus Telmatobius (Anura: Leptodactylidae) from Tucumán Province, Argentina.'' Herpetologica, 64(1), 47-62.

Benavides, E. (2005). ''The Telmatobius species complex in Lake Titicaca: applying phylogeographic and coalescent approaches to evolutionary studies of highly polymorphic Andean frogs.'' Studies on the Andean Frogs of the Genera Telmatobius and Batrachophrynus (Anura: Leptodactylidae). Monografías de Herpetología, 7. E. O. Lavilla and I. De La Riva, eds., Asociación Herpetológica Española, Valencia.

Benavides, E., Ortiz, J. C., and Sites, J. W. (2002). ''Species boundaries among the Telmatobius (Anura: Leptodactylidae) of the Lake Titicaca Basin: allozyme and morphological evidence.'' Herpetologica, 58(1), 31-55.

Garman, S. (1876). ''Exploration of Lake Titicaca.'' Bulletin of the Museum of Comparative Zoology, 3, 273-278.

Hutchison, V. H., Haines, H. B., and Engbretson, G. (1976). ''Aquatic life at high altitude: respiratory adaptations in the Lake Titicaca frog, Telmatobius culeus.'' Respiration Physiology, 27, 115-129.

Macedo, H. (1960). ''Vergleichende Untersuchungen an Arten der Gattung Telmatobius.'' Zeitschrift für Wissenschaftliche Zoologie, 163, 355-396.

Merino-Viteri, A., Coloma, L. A., Almendáriz, A. (2005). ''Los Telmatobius (Leptodactylidae) de los Andes de Ecuador y su disminución poblacional.'' Monografías de Herpetología, 7, 9-37.

Perez Bejar, M. E. (2005). ''Cria en cautividad y uso sostenible de la rana gigante del Lago Titicaca (Telmatobius culeus).'' Mono­grafias de Herpetologia, 7, 261-271.

Pérez, M. B. (1998). Dieta y ciclo gametogénico anual de Telmatobius culeus (Anura, Leptodactylidae) en el Lago Titicaca (Huiñaimarca). Tesis de Licenciatura, Universidad Mayor de San Andrés, La Paz, Bolivia.

Ruiz, G., Rosenmann, M., and Veloso, A. (1983). ''Respiratory and hematological adaptations to high altitude in Telmatobius frogs from the Chilean Andes.'' Comparative Biochemistry and Physiology, 76A(1), 109-113.

Seimon, T. A., Hoernig, G., Sowell, P., Halloy, S., and Seimon, A. (2005). ''Identification of chytridiomycosis in Telmatobius marmoratus at 4,450 m in the Cordillera Vilcanota of southern Peru.'' Studies on the Andean Frogs of the Genera Telmatobius and Batrachophrynus, Monografías de Herpetología, 7. E. O. Lavilla and I. De La Riva, eds., Asociación Herpetológica Española, Valencia.

Seimon, T. A., Seimon, A., Daszak, P., Halloys, S. R. P., Schloegel, L. M., Aguilar, C., Sowell, P., Hyatt, A. D., Konecky, B., and Simmons, J. E. (2007). ''Upward range extension of Andean anurans and chytridiomycosis to extreme elevations in response to tropical deglaciation.'' Global Change Biology, 13, 288-299.

Sinsch, U., Salas, A. W., and Canales, V. (1995). ''Reassessment of central Peruvian Telmatobiinae (genera Batrachophrynus and Telmatobius). I. Morphometry and classification. .'' Alytes, 13, 14-44.

Stuart, S., Hoffmann, M., Chanson, J., Cox, N., Berridge, R., Ramani, P., Young, B. (eds) (2008). Threatened Amphibians of the World. Lynx Edicions, IUCN, and Conservation International, Barcelona, Spain; Gland, Switzerland; and Arlington, Virginia, USA.

Species Account Citation: AmphibiaWeb 2024 Telmatobius culeus: Titicaca Water Frog <https://amphibiaweb.org/species/2695> University of California, Berkeley, CA, USA. Accessed May 31, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 31 May 2025.

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