"According to the press release accompanying the new paper, the leopard
frogs in the region were noted as having a croak that was quite distinct
from those of the two species that inhabit the northern and southern
parts of the East Coast. (A researcher involved in the finding described
the other species as having a “long snore” or a “rapid chuckle.”)
Speculation had focused on the possibility that the New York frogs were a hybrid of the two species, but molecular evidence shows that they are distant from both."
Source:
http://www.wired.com/wiredscience/2012/03/new-frog-species-nyc