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A very common and widely distributed South American frog Leptodactylus fuscus is known by several common names including the rufous frog, fuscous foam frog and lineated frog. This species occurs from the Pacific lowlands of Panama through South America east of the Andes and south to southern Brazil, Bolivia and northern Argentina. It is also found in Trinidad and Tobago. More research is needed to determine whether this taxon is a highly variable or a species complex of more than one species. Molecular analysis indicates that it includes three separate evolutionary lineages, which show distinct reproductive ecologies and calling behavior across its large range (Heyer and Ried 2003; Camargo and Heyer 2006). Wynn and Heyer (2001) suggest that L. fuscus originated south of the Amazon river, and subsequently dispersed north.
The rufous frog is terrestrial, found primarily in open areas at elevations below 1700 m. It inhabits savannahs, marshes, grasslands near water, or in areas that flood seasonally. This frog also survives well in disturbed habitats such as degraded forests, pastures, plantations, canals and ditches and urban areas. The rufous frog does not have webbed feet. It is largely sedentary, and active at night, and a generalist feeder (Smithsonian Tropical Research Institute 2016; Araújo et al. 2007).
A medium-sized foamfrog, the lineated frog has a green/brown back, with darker brown spots. They have six ridges (skin folds) that run down their back, from their head to rear. Some individuals have a white stripe down the center. Its large eyes have a bronze-colored iris. A dark line runs long the back of the thigh. Its belly is white, and unpatterned. The throat on makes is dark grey or black. Males grow to 53 mm in snout-vent length, and females are slightly larger, up to 56 mm (Smithsonian Tropical Research Institute 2016).
Rufous frog reproduction generally occurs at night, during rainy periods when temperatures are high. Males dig burrows adjacent to water bodies or in temporary wetlands before they are inundated, and start calling at the onset of the very first rains. Their call is a short, whistly, rising note. Mating occurs and together the male and female produce a foam nest in the burrow. Females then deposit the eggs in the nest. The tadpoles develop inside the foam but pause their development when they reach feeding stage. When heavy rains come, they wash the tadpoles out of the nest into nearby flooded rivers or inundated marsh areas. Tadpoles immediately begin feeding and complete development in the water. If the tadpoles’ watersupply dries up, they are also capable of surrounding themselves with foam they generate to prevent dessication, and then hide (often in groups) in the mud under rocks (Downie 1984, 1994; Lucas et al. 2008; Maragno, F.P. and Cechin, S.Z., 2009; Smithsonian Tropical Research Institute 2016).
Smithsonian Tropical Research Institute, 2016. Leptodactylus fuscus. Amphibians of Panama. Smithsonian Institution. Retrieved March 21, 2016 from http://biogeodb.stri.si.edu/amphibians/en/species/139/
Araújo, MS, DI Bolnick, G Machado, AA Giaretta and SF dos Reis. 2007. Using δ13C stable isotopes to quantify individual-level diet variation. Oecologia 152(4): 643-654.
Camargo, A, R O de Sa, and WR Heyer. 2006. Phylogenetic analyses of mtDNA sequences reveal three cryptic lineages in the widespread neotropical frog Leptodactylus fuscus (Schneider, 1799) (Anura, Leptodactylidae). Biological Journal of the Linnean Society 87(2): 325-341.
Downie, J.R., 1984. How Leptodactylus fuscus tadpoles make foam, and why. Copeia, 1984(3), pp.778-780.
Downie, JR. 1994. Developmental arrest in Leptodactylus fuscus tadpoles (Anura: Leptodactylidae). I: Descriptive analysis. Herpetological journal 4(2): 29-38.
Heyer, W.R. and Reid, Y.R., 2003. Does advertisement call variation coincide with genetic variation in the genetically diverse frog taxon currently known as Leptodactylus fuscus (Amphibia: Leptodactylidae)?. Anais da Academia Brasileira de Ciências, 75(1), pp.39-54.
Lucas, E.M., Brasileiro, C.A., Oyamaguchi, H.M. and Martins, M., 2008. The reproductive ecology of Leptodactylus fuscus (Anura, Leptodactylidae): new data from natural temporary ponds in the Brazilian Cerrado and a review throughout its distribution. Journal of Natural History, 42(35-36), pp.2305-2320.
Maragno, F.P. and Cechin, S.Z., 2009. Reproductive biology of Leptodactylus fuscus (Anura, Leptodactylidae) in the subtropical climate, Rio Grande do Sul, Brazil. Iheringia. Série Zoologia, 99(3), pp.237-241.
Wynn, A. and W. R. Heyer, 2001. Do geographically widespread species of tropical amphibians exist? An estimate of genetic relatedness within the neotropical frog Leptodactylus fuscus (Schneider 1799) (Anura Leptodactylidae), Tropical Zoology, 14:2, 255-285, DOI: 10.1080/03946975.2001.10531157