Criolla Frog

Female: 80-110 mm, Male: 90- 120 mm. Dorsum dark, grey or reddish-brown with prominent longitudinal folds and large dark white- edged spots (ocelli). Largest ocellus between eyes. Belly whitish, scarcely mottled with grey. Throat dark spotted. Male with strongly developed forearms and two black thorns on the first finger. Toes with fringes. Inner side of femoral grey with dark bar pattern. Looks similar to Leptodactyus chaquensis (greenish femoral without bar pattern).See Lavilla et al. (2010) for the most recent taxonomic changes, synonymizing L. ocellatus with L. latrans.

It inhabits open grassland, very often found at ponds, small lakes or flooded areas. Regions: Atlantic coast, elevated plains and pampas (lowlands of South America). Countries: South Brazil, Argentina, Uruguay and East Paraguay.

The diurnal and nocturnal frogs are frequently found resting at the margin of ponds or small lakes and jump into the water if disturbed. They are good swimmers but may also walk and run over land; the toe fringes allow for both, whereas webbed toes would hinder terrestrial activities. L. ocellatus is carnivorous; their diet consists of insects and their larvae, arachnids, myriapods, and annelids. Larvae are agile and free-swimming omnivores, feeding on microorganisms, periphyton or carrion. Predators of the species are mainly birds. Predators of the larvae also include water insects, carnivorous tadpoles and snakes. During the breeding time, i.e. from September to February, the males hide in aquatic vegetation and call with short monotonous notes at low pitch. Calls are louder and more frequent before rain, as the eggs are usually laid into seasonal ponds. Males beat glandular secretions of the female into a foamy mass while still on the female’s back, so the several thousand small black eggs are sheltered in a foam nest that will float on a water surface. The thumb spines or thorns in males are thought to give them a better grip during amplexus, when the males beat up the foam nest. A usual nest is between 12 and 25 cm in diameter and often has a central hole of 4 to 8 cm width. This foam nest lowers the predation risk for eggs and larvae and keeps them moist in the seasonal ponds of tropical regions. In dry ponds shortly before heavy rainfalls, the foam nest is deposited, and eggs may even hatch in the nest and the larvae be released on the next rain, which will destroy the nest and fill the pond with water again. The larvae of L. ocellatus then have an evolutionary advantage over other larvae as they are further developed and may start metamorphosis earlier, before the pond may again fall dry. Seasonality of the ponds also ensures a lower predation risk for the larvae, because there are no fishes in seasonal ponds and other predators such as water insects and carnivorous tadpoles develop later after the filling of the pond. Females are characterized by extended maternal care. They are often found sitting in the nest hole with the head poking out or beneath the nest, and they show threatening and biting behavior toward predators. Hatched larvae aggregate and move together in gregarious shoals, mostly accompanied by the mother in less than 1 m distance. Mothers will stay with the larvae both during the night and day and defend them against predation, especially birds such as the benteveo (Pitangus sulphuratus argentinus). On sight of a bird, the mother beats the water surface, so the larvae realize coming danger and rapidly hide beneath the mother. Interestingly, the adult frogs may change the length of their guts in relation with feeding season and reproductive status. In L. ocellatus, the stomach of both sexes and the intestine in males is longer during the hot, high feeding season; the length of the female intestine is highest during the cold season and correlated with high estrogen levels, which occur shortly before spawning, so female intestine length is related to yolk production.

L. latrans (formerly known as L. ocellatus) is a common species in the Neotropical region.

Leptodactylus latrans is a species of frog in the family Leptodactylidae. It is native to much of South America east of the Andes, and Trinidad and Tobago. It has many common names, including rana criolla, sapo-rana llanero, butter frog, and lesser foam frog.