The croak gave it away.
On a foray into the wilds of Staten Island in 2009, Jeremy A. Feinberg, a doctoral candidate in ecology and evolution at Rutgers University, heard something strange as he listened for the distinctive mating call of the southern leopard frog — usually a repetitive chuckle. But this was a single cluck.
“I started hearing these calls, and I realized they were really distinct,” Mr. Feinberg said.
Three years later, Mr. Feinberg and four other scientists who joined him in multiple field and laboratory studies, are finally comfortable making their declaration: a new species of leopard frog — as yet unnamed — has been identified in New York City and a number of surrounding counties.
The find is surprising on a number of fronts, not least of which is that the new frog was hiding in plain sight in one of the most populated centers in the world. (Most new species are found in remote areas.) And it illustrates the power of genetic testing in parsing more finely those animals that may be nearly identical in appearance, but are, in fact, of different species.
There are more than a dozen leopard frogs, ranging from Canada to Central America. Medium in size, with dark spots on a tan, olive or green background, they gravitate toward grassy meadows and breed in ponds or pools. The researchers say that the new frog species was confused for a long time with the southern leopard frog, which it closely resembles.
Its known range is limited, more or less, to commuting distance from Midtown Manhattan, stretching from around Trenton, N.J., in the south, to Putnam County, N.Y., to the north.
“Here is a brand-new species, and it’s not a species of bacteria or a barely visible insect,” said H. Bradley Shaffer, a professor in the department of ecology and evolutionary biology at the University of California at Los Angeles. “It’s a big amphibian, and kids have probably been catching and playing with it for years,” he said. “Even in an urban center like New York, where herpetologists have tromped all over for a century or more, there can be new species out there. That shows the importance of urban areas in terms of conservation and biodiversity.”
The findings are to be published in an issue of the journal Molecular Phylogenetics and Evolution, but are currently available online. Much of the genetic analysis was performed in Professor Shaffer’s laboratory at the University of California at Davis, where he worked until recently.
There, with his encouragement, Catherine E. Newman, an evolutionary biologist who had done her master’s thesis on the southern leopard frog, studied the frog’s DNA, taken from samples sent by Mr. Feinberg and others. She compared it with the DNA of southern and northern leopard frogs, which range widely north and south of New York City.
Local amphibian fans can be forgiven for not noticing the new frog’s unique nature. “I wouldn’t know which one I was holding because they all look so similar,” said Ms. Newman, who is now pursuing her Ph.D. at Louisiana State University. “But all of our results showed this one’s lineage is very clearly genetically distinct.”
So far, Mr. Feinberg has positively identified the new species on Staten Island, although he says it probably once inhabited Manhattan and the other boroughs. He has found specimens in the Meadowlands and the Great Swamp National Wildlife Refuge in New Jersey, and Putnam and Orange Counties in New York. Some frogs were also collected in central Connecticut.
“It’s a very small range and even if we went back 400 to 500 years, it probably would have been considered a rare animal,” he said.
The dead center of the known range, oddly, is near Yankee Stadium, even though the frog has not yet been found in the Bronx.
“I think that at this point it’s very important to do additional surveys,” Professor Shaffer said. The frog’s range “may be no wider than we have found or it may be wider.”
Over the years, a few other scientists almost identified the new species, but fell short. In 1936, one esteemed herpetologist wrote that he suspected there was a third frog species in the general New York City area. But he did not investigate further.
In the early 1970s, another scientist went on a listening tour of the various leopard frogs’ mating calls while driving from Florida to the Northeast. “She missed this entire area,” Mr. Feinberg said. “She might have been driving on I-95 and just skipped over the weird call area.”
As the lead author on a second paper that is to explore the physical characteristics and call of the new frog, Mr. Feinberg will have the honor of naming rights, choosing a scientific and common name. For now he’s not letting the frog out of the bag.
“I’ve given it lots of thought,” he said. “Part of me has always wanted to call these New York leopard frogs, but I think people in New Jersey and Connecticut will protest. I have to balance the politics with the naming.”
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