Description
Ceratophrys calcarata is a charismatic, terrestrial, burrowing frog first described by the British naturalist G.A. Boulenger in 1890. Specimens in this species have been recorded to have a snout-vent length that ranges from about 60 mm to 70 mm, with females skewing larger (Boulenger 1890, Murphy 1976, Schalk et al. 2014). Its head is large and contains a visible paired cranial ridge. The nostril is closer to the eye than the snout tip. The tympanum is extremely distinct and smaller than the eye. Its interorbital space is concave. Typical of its genus, C. calcarata has a prolonged upper eyelid that extends into a “horn” shape. Its tibiotarsal articulations are can extend to touch the tympanum. The upper sections of the fingers has small, though prominent tubercles; the larger tubercles are ribbed (Boulenger 1890). Its third toe is longer than the fifth and is as long as the first phalange bone of the fourth toe (Murphy 1976). Ceratophrys calcarata has obvious webbing on its toes that reach the basal subarticular tubercles. The outer and inner toes having roughly the same amount of webbing (Lynch 1982).

DIAGNOSIS:

There are lateral folds along the inner margin of C. calcarata’s tarsus like the other frogs in its clade: C. cornuta and C. stolzmanni. The Ceratophrys that dwell farther south, C. aurita, C. cranwelli, and C. ornata, have tarsal folds in a more inset position. The indentations in the back of C. calcarata’s head look deeper due to its prominent, posterior-pointing optic crests. Ceratophrys aurita, C. cranwelli, and C. ornata have lateral and media plates instead of crests. Ceratophrys calcarata has no co-ossified vertebral shield, differentiating it from its three southern counterparts that do have shields. Its feet have webbing that is of equal length between inner and outer toes. The webbing of C. cranwelli and C. ornata is reduced in toes IV and V, and the webbing of C. aurita has more extensive webbing on its inner toes than the outer toes. Ceratophrys calcarata has extensive cone-shaped horns/tubercles near its eyes, which is in contrast to C. cranwelli’s fleshier eyelid appendages. Ceratophrys ornata has miniscule eye horns, and C. stolzmanni lacks them entirely. The throat and breast of C. calcarata is are potted and dark with markings that coalesce into a more solid color, whereas C. aurita and C. cornuta have uniformly dark throats (Lynch 1982).

COLORATION:

In alcohol, the frog is dark olive dorsally with paler green symmetrical markings. It has an arrow-headed green band on the back that widened and split between its eyes. The lower part of the frog has brown spots. Its wrists are black (Boulenger 1890).

VARIATION:

Rather than having short “horns” on its upper eyelids, some C. calcarata have large cone-shaped tubercles on the same area (Lynch 1982).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Colombia, Venezuela

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (1 records).

This frog is found in northern Colombia and Venezuela (Lynch 1982). It tends to settle in forest, savanna, shrub-land, inland wetlands, and grassland habitats. Due to urbanization, it can be found near human settlements and within artificial ditches (IUCN 2020).

Life History, Abundance, Activity, and Special Behaviors
Like other Ceratophryids, C. calcarata is fossorial and active during rainy seasons (Faivovich et al. 2014). It can bury itself in the ground and remain dormant for up to six months (IUCN 2020).

The carnivorous diet of C. calcarata consists primarily of arthropods—namely coleopterans—vertebrates, rodents, and small reptiles (Schalk 2014). Ceratophrys calcarata engages in pedal luring to entice its smaller prey. During pedal luring, it raises its hind limbs slowly and draws its foot closely to its body. Then it vibrates and undulates its toes, revealing its inner metatarsal tubercle. This motion “beckons” prey to approach C. calcarata, allowing the frog to pounce on its food (Murphy 1976).

Ceratophrys calcarata produces an antimicrobial peptide called waprin utilized for amphibian innate immunity, chemical defense against predators, and killing microorganisms and parasites that infect its body. It secretes a ceratoxin from the waprin family of toxins, which is comparable to snake venom, from its skin. The discovery of this antimicrobial peptide indicated a potential evolutionary connection between reptile and amphibian waprins (Liu et al. 2012).

Larva
The tadpole of C. calcarata resembles other tadpoles in the genus, namely C. aurita, C. cornuta, and C. ornata. It has a bulky body, strong beaks, expanded lips with one row of long papillae, and medial vent lacking a tube (La Marca 1986).

Trends and Threats
This frog is sensitive to fluctuations in temperature. Due to the raising of minimum temperatures in South America, habitats suitable for C. calcarata will expand exponentially in approximately 60 years, therefore skyrocketing its present distribution. This makes C. calcarata—along with C. cranwelli, which has a similar reaction to oscillating temperatures—unique compared to other Ceratophryids (Vieira et al. 2018).

Relation to Humans
The genus Ceratophrys is popular in the international exotic pet trade. Ceratophrys calcarata has been found in pet shops in Taiwan (Hou et al. 2005) as well as in other countries.

Comments

PHYLOGENETIC RELATIONSHIPS:

References
Boulenger, G. A. 1890. Second report on additions to the batrachian collection in the Natural-History Museum. Proceedings of the Zoological Society of London 1890, 323–328. [link]

Faivovich, J., Nicoli, L., Blotto, B. L., Pereyra, M. O., Baldo, D., Barrionuevo, J. S., Fabrezi, M., Wild, E. R., and Haddad, C. F. B. (2014). Big, bad, and beautiful: Phylogenetic relationships of the Horned Frogs (Anura: Ceratophryidae). South American Journal of Herpetology, 9(3), 207. [link]

Gómez, R. O., and Turazzini, G. F. (2021). The fossil record and phylogeny of South American Horned Frogs (Anura, Ceratophryidae). Journal of Systematic Palaeontology, 19(2), 91–130. [link]

IUCN SSC Amphibian Specialist Group. 2020. Ceratophrys calcarata. The IUCN Red List of Threatened Species 2020: e.T56336A85857371. https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T56336A85857371.en. Accessed in September 2024

Hou, P.-C. L., Shiau, T.-W., Tu, M.-C., Chen, Chen, T.-Y., Tsai, Y.-F., Lin, C.-F., and Wu, S.-H. (2006). Exotic Amphibians in the Pet Shops of Taiwan. Taiwania, 51(2), 87–92. [link]

Liu, D., Wang, Y., Wei, L., Ye, H., Liu, H., Wang, L., Liu, R., Li, D., and Lai, R. (2013). Snake venom-like waprin from the frog of Ceratophrys calcarata contains antimicrobial function. Gene, 514(2), 99–104. [link]

La Marca, E. (1986). Description of the tadpole of Ceratophrys calcarata. Journal of Herpetology, 20(3), 459. [link]

Lynch, J. D. (1982). Relationships of the frogs of the genus Ceratophrys (Leptodactylidae) and their bearing on hypotheses of Pleistocene forest refugia in South America and punctuated equilibria. Systematic Zoology, 31(2), 166. [link]

Murphy, J. (1976). Pedal luring in the Leptodactylid Frog, Ceratophrys calcarata Boulenger. Herpetologica, 32(3), 339–341. [link]

Schalk, C. M., Montaña, C. G., Klemish, J. L., and Wild, E. R. (2014). On the diet of the frogs of the ceratophryidae: synopsis and new contributions. South American Journal of Herpetology, 9(2), 90–105. [link]

Vieira, K. S., Montenegro, P. F., Santana, G. G., and Vieira, W. L. (2018). Effect of climate change on distribution of species of common horned frogs in South America. PLOS ONE, 13(9). [link]

Species Account Citation: AmphibiaWeb 2024 Ceratophrys calcarata: Venezuelan Horned Frog <https://amphibiaweb.org/species/5719> University of California, Berkeley, CA, USA. Accessed Feb 7, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 7 Feb 2025.

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