New Brunswick - Scientists have discovered a new species of leopard frog in the New York City metropolitan area and its surrounding coastal regions.
Named Rana kauffeldi, it had long remained undetected because it is a "cryptic species", one whose appearance makes it almost indistinguishable from a closely related species.
But its mating calls, in particular, are distinct, the scientists report in the online scientific journal PLOS ONE.
"This discovery is unexpected in one of the largest and most densely populated urban parts of the world," they said. "It also demonstrates that new vertebrate species can still be found periodically, even in well-studied locales rarely associated with undocumented biodiversity."
Field studies in 2012 had brought the first genetic evidence of a new frog species in the New York City region, where the similar leopard frog species, Rana pipiens und Rana sphenocephala, live.
As early as the 1930s, the American herpetologist Carl F Kauffeld suspected the presence of a third species.
Various frog species
A research team led by Jeremy Feinberg, a doctoral student at the Rutgers University School of Environmental and Biological Sciences in the US state of New Jersey, analysed mating calls of the various frog species along with minute differences in appearance and genetic markers.
The results showed that a previously undescribed species of leopard frog lives in eight eastern US states. The scientists named it Rana kauffeldi in honour of Kauffeld.
Rana kauffeldi inhabits moderately moist lowlands including coastal freshwater wetlands, tidally influenced backwaters, and interior river valley floodplains, the scientists said. Its colour ranges from light green to dark brown with black spotting.
During the mating season, males congregate in groups of typically five or more and make low-pitched calls that do not carry far.
The scientists said that Rana kauffeldi was the first newly described anuran - an order of amphibians comprising frogs, toads, and tree frogs - from the US Atlantic coast since 1955. Some specimens were found less than 15km from the Statue of Liberty.
Feinberg's team first reported the new species in 2012 in the scientific journal Molecular Phylogenetics and Evolution.