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The túngara frog, Engystomops pustulosus, is a small, warty frog of Central America best known for a mating call so distinctive that it has made the species a textbook case in the study of sexual selection. It ranges across Mexico through Central America into northern South America, east to Trinidad and Tobago, Venezuela and possibly Guyana, and it tolerates people well, turning up in suburban gardens and roadside ditches as readily as in undisturbed forest.
Identification
Adults are small, measuring 25–35 mm snout-vent length; the facts box carries the exact range. The warty, bumpy skin on the back once led early naturalists to classify the species among the true toads, but it is a true frog with a hidden tympanum (no visible eardrum) and relatively large, protruding eyes. Both sexes usually show a conspicuous white stripe running from the lower lip down the throat, while males carry a large, dark, inflatable vocal sac that females lack. Colour pattern varies with habitat: striped and unstriped forms occur depending on predation pressure, and striped individuals are more common in urban areas than in forest.
Habitat and range
The species occupies lowland savannas and open environments, natural and disturbed humid lowland and montane forest, and tropical dry forest, but it is at its most common around human-made water bodies such as temporary or permanent ponds, puddles, ditches and potholes. That tolerance for altered ground lets it persist in suburbs and parks well inside the edges of its wider Mexico-to-South-America range.
Behaviour and breeding
Túngara frogs are nocturnal, emerging at night to feed on ants, termites and other small invertebrates such as snails, beetles, flies and isopods found in leaf litter. Males call from the edges of ponds with a two-part signal: a long, frequency-modulated “whine” sweeping from about 900 Hz to 400 Hz and lasting roughly 300 ms, which can be followed by one or more short, sharp bursts called “chucks,” each about 45 ms long and dominated by frequencies around 2,500 Hz. A male calling alone tends to produce the simple whine-only call, but adds chucks to build a more complex call when calling in a chorus with other males. Females are drawn to complex calls over simple ones, and to lower-frequency chucks, which signal a larger male — but a more elaborate call also carries a cost, since complex calls make males easier for fringe-lipped bats to find and catch, the species’ most specialised predator alongside larger frogs, opossums and crabs.
Mating itself produces one of the frog’s more unusual traits: while paired in amplexus, the male whisks a foam-producing fluid released by the female into a floating foam nest that shields the fertilised eggs. Tadpoles develop in the water beneath the foam for roughly four weeks before metamorphosing into juveniles, and the spent nest itself can persist for up to two weeks after the tadpoles have left it.
Conservation
The species’ facts box carries its current IUCN Red List category, Least Concern, reflecting its broad range and its ability to breed in disturbed and human-made habitats. Even so, studies of frogs living on agricultural land have found decreased egg numbers, reduced hatching success and smaller body size compared with frogs from less disturbed sites: local habitat change and pollution can still affect a species with a broad range and a stable status.
Similar species
The warty skin of E. pustulosus has long invited confusion with true toads, but its hidden tympanum, large eyes and the male’s distinctive two-part whine-and-chuck call set it apart. No other species profile on this site currently covers a close relative in the genus Engystomops or the wider family Leiuperidae.