Sunday, July 9, 2017

Tungara Frog, Engystomops pustulosus (Family Leiuperidae)

Previously known as Eupemphix pustulosus trinitatis and Physalaemus pustulosus.

Size: small terrestrial frogs, males 28 mm, females 32 mm SVL.

Identification: Dorsal skin highly tubercular, arranged more or less in longitudinal rows; lateral skin also tubercular. Dorsum brown-grey with darker spots along tubercle rows. Ventral skin granular, tan to yellow. Dorsal surface of hind limbs cross-barred. Snout pointed in dorsal view, rounded in profile. Tympanum indistinct. Small triangular parotoid gland present. All digits lack webbing and adhesive discs. Toes have a slight lateral fringe.

Similar species: The size, shape, wariness, and vocalizations of tungara frogs make them readily distinguishable.

Distribution and habitat: The genus Engystomops contains nine species, distributed from southern Mexico to northern South America and on to Bolivia.

Vocalization: There are two components to the call, a resonant ‘poong’ followed by a series of short ‘chucks’- ch,ch,ch. Complexity added by the chucks helps to attract females, but it also attracts predatory bats, so in the presence of bats, the male frogs simplify their calls.

Research indicates that the E. pustulosus is a very widespread species, from Mexico, south through Central America and Amazonia. 

Although there is considerable variation there is no firm basis to subdivide the population into different species. E. pustulosus is very common in both Trinidad and Tobago, mainly in lowland grasslands, forest fringes and in towns as a human commensal (often co-occurring with Leptodactylus fuscus).

Biology: Diet not reported. Mating pairs generate white floating foam nests, about 6-8 cm, in the open at the edges of ponds, choked ditches, even water-filled tire ruts. Each nest contains 300-500 creamy white eggs which hatch into the water below after about 2 days. 

Tadpoles are capable of metamorphosis after about three weeks, at which time they reach a maximum length of about 22 mm. Body rounded, tail tapered. Overall coloring pale gray/brown. These tadpoles are cryptically colored and tend to be found in the sediment at the bottom of temporary pools. Newly metamorphosed individuals are about 9 mm SVL and look like miniature adults.

Conservation status: Least Concern on account of its wide distribution, tolerance of a wide range of habitats, and presumed large population.

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