Description
Lepidobatrachus laevis is a large, stout, aquatic frog with a dorsoventrally flattened body. Females of this species may reach a total body length (SVL) of 100 mm, while a sexually mature male may be only half as large. In both sexes the head is large and robust, composing approximately 1/3 of the total body length, and broad to make room for the extraordinarily wide jaws of these animals. There are large teeth on the upper jaw and two large medially placed teeth or fangs on the lower jaw. The nostrils and eyes are dorsally positioned, the pupils are rhomboidal and the tympanum is distinct. The forelimbs and hind limbs are short, and the forelimbs are held forward while swimming. The digits of the forelimbs are unwebbed, but the digits of the hind limb are fully webbed and a large, spade-like, black inner metatarsal tubercle is present. The skin is mostly smooth except for the raised dorsal glandulae of the lateral line, which are distinct and from a “V” that narrows posteriorly. The dorsal coloration of L. laevis is dark green to gray with darker blotches outlined in orange that becomes more visible laterally. The nostrils and eyes may be outlined by lighter green, perhaps providing camouflage. The ventral surface is white or cream colored and unmarked. Sexually mature males possess a dark blue-black throat (Budgett 1899; Cei 1980).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Argentina, Bolivia, Paraguay

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (5 records).

L. laevis occur in the Gran Chaco of South America, a semiarid region extending into northern Argentina, southern Paraguay, and much of Bolivia. In Argentina this species can be found in the provinces of Chaco, Cordoba, Corrientes, Salta, Santa Fe, Santiago del Estero (Faivovich 1994). Within Paraguay it is found in the departments of Alto Paraguay, Boquerón, and Presidente Hayes in Paraguay (Faivovich 1994). In Bolivia it occurs within the departments of Santa Cruz and Tarija (Aquino et al. 2004). Its altitudinal range is from 0-200 m asl (Aquino et al. 2004).

Within the chaco, L. laevis is found in ephemeral pools (pozos) that form during the summer rains from October to February. During the wet summer months these frogs feed and breed in the pozos. As the pools dry up at the end of summer the animals burrow into the soft mud using the large tubercles on their hind limbs. They remain inactive underground during the dry winter months.

Life History, Abundance, Activity, and Special Behaviors
L. laevis displays a suite of interesting adaptations to the semiarid environment of the Gran Chaco. The rhythm of activity of the adults of this species is synchronized with the extreme climate of this region of South America. During the dry winter months L. laevis remains inactive underground, encased in a hard shell composed of layers of unshed skin. This “cocoon” protects the animal from excessive water loss and allows it to persist until the rains arrive that signal the beginning of the wet summer months, which typically last from October to February. The heavy spring or summer rains flood the chaco and create many temporary pools or “pozos” which provide suitable habitat for L. laevis.

Once the pools form L. laevis emerge from their cocoons to feed and breed. These frogs appear to be nocturnal sit-and-wait ambush predators. They remain motionless while submerged in the water or soft mud with only their eyes and nostrils visible. There they wait among grasses and reeds for prey to come within grasp of their strong, powerful jaws. The large size of these frogs and the size of their jaws imply that they feed on large prey, most likely other anurans, large insects and snails. In general these are very aggressive frogs. When disturbed, they inflate themselves and stand on their outstretched limbs to appear larger. If this fails to deter a potential predator, they begin to lunge, bite, and then emit a piercing shriek. This behavior is quite impressive and provides the name for this species in Guarani - kukurú-chiní or “the toad that shrieks” (Vellard 1948).

The reproductive biology and larval ecology of L. laevis provide additional examples of the fascinating biology of this particular species of frog. A single breeding event may result in as many as 1400 fertile eggs. The embryos develop very rapidly, a characteristic of many desert anurans that often are in a race against time to metamorphose into adults before their breeding pool dries up. When the tadpoles hatch and begin feeding, however, their uniqueness becomes even more apparent. The tadpoles are carnivorous and cannibalistic and begin feeding almost immediately. Although carnivory and cannibalism are relatively rare among larval anurans, it is the morphology of the jaws of L. laevis tadpoles which sets them apart. Unlike other carnivorous anuran larvae, L. laevis possess nearly adult-like jaws. The cartilages that support the larval jaws are expanded laterally to create a wide, gaping mouth which the tadpoles of this species use to ingest their prey whole. Ruibal and Thomas (1988) illustrate this feeding apparatus in detail and coin the term “megalophagy” to describe the unique larval feeding ecology.

Trends and Threats
This species is thought to be more common in Bolivia (the northern portion of its range) and rare in Argentina (Aquino et al. 2004). In spite of the many interesting features of the ecology and morphology of L. laevis, this species remains poorly known. This is perhaps because of their secretive nature, nocturnal habits and long period of inactivity during the dry season. Also, these frogs do not appear to be particularly abundant where they occur. These factors, combined with their strict habitat requirements, make L. laevis vulnerable to habitat modification associated with agriculture and ranching where they occur. This species is also apparently susceptible to chytridiomycosis, with one death reported in a captive specimen (Une et al. 2008).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Local pesticides, fertilizers, and pollutants

References

Aquino, L., De La Riva, I., and Céspedez, J. (2004). Lepidobatrachus laevis. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.1. www.iucnredlist.org. Downloaded on 22 June 2009.

Budgett, J. S. (1899). ''Notes on the batrachians of the Paraguayan chaco, with observations upon their breeding habits and development, especially with regard to Phyllomedusa hypochondrialis, Cope. Also a description of a new genus.'' The Quarterly Journal of Microscopical Science, 42(167), 305-333.

Cei, J. M. (1980). ''Amphibians of Argentina.'' Monitore Zoologica Italiano, New Series Monografia, Firenze, 2, 1-609.

Faivovich, J. (1994). ''La distribución del género Lepidobatrachus (Budgett, 1899) (Leptodactylidae: Ceratophryinae).'' Acta Zoologica Lilloana, 43(1), 137-174.

Lavilla, E. O., and Cei, J. M. (2001). Amphibians of Argentina, A Second Update, 1987-2000. Museo Regionale di Scienze Naturali, Torino.

Ruibal, R., and Thomas, E. (1988). ''The obligate carnivorous larvae of the frog Lepidobatrachus laevis (Leptodactylidae).'' Copeia, 1988(3), 591-604.

Une, Y., Kadekaru, S., Tamukai, K., Goka, K., and Kuroki, T. (2008). ''First report of spontaneous chytridiomycosis in frogs in Asia .'' Diseases of Aquatic Organisms, 82, 157-160.

Vellard, J. (1948). ''Batracios del chaco argentino.'' Acta Zoologica Lilloana, 5, 137-174.

Species Account Citation: AmphibiaWeb 2009 Lepidobatrachus laevis: Budgett's Frog <https://amphibiaweb.org/species/5602> University of California, Berkeley, CA, USA. Accessed Nov 23, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 23 Nov 2024.

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