Kiawah Island’s Voices of the Night
I
By Whit Gibbons
8
Photo by David E. Scott
Southern leopard frog.
Photo by Tom Luhring
Eastern narrowmouth toad.
Southern toad.
Photo by JD Willson
all still there, and we remain friends. I began surveys of the Kiawah
Island “herpetofauna,” the collective term for reptiles and amphibians,
in July 1974. On my first rainy night that month, I experienced the most
deafening chorus of squirrel treefrogs and green treefrogs I had ever heard.
The incessant quacking of the two came from a freshwater ditch behind the sand
dunes near what is now Night Heron Park. Their noise almost overpowered the
chuckles of leopard frogs. An unceasing lamb-like bleating of narrowmouth toads
and harmonious trill of southern toads provided a fine backdrop for this natural
symphony. The discordant “qwaah” of hundreds of croaking spadefoot toads
detracted from the musical score, but the cacophony from this seldom seen species
was a true indicator of a major downpour.
These six kinds of “anurans,” the collective name for frogs and toads, would
soon prove to be the full complement native to Kiawah Island. After four years
of ecological research and surveys, we never found another species of anuran,
although we heard or saw each of the six many other times. The same holds true
even after numerous visits over the next four decades, mostly to conduct studies
on the diamondback terrapins in the Kiawah River and saltmarshes.
Frogs, toads, and treefrogs are some of the most amazing animals on earth.
More than 6,800 living species are known today worldwide. Most are tropical,
and less than 1.5 percent occur in the United States. Nonetheless, the Southeast
has its share of frog diversity with approximately half of the country’s species.
Early herpetofaunal research that led to ecological insights and discoveries on
Kiawah Island was published in scientific journals. Kiawah became recognized by
the scientific community for having the most thorough herpetofaunal research
ever conducted on any of the Atlantic Coast barrier islands. Thus it served as the
touchstone for one study comparing its biodiversity to eight other barrier islands
from Cape Hatteras, NC, to Cumberland Island, GA, on which surveys
of herpetofaunal biodiversity had been conducted.
One ecological revelation was that the same six species of frogs and toads found
on Kiawah were also found on all or at least a majority of the barrier islands.
In contrast, certain species common on the mainland were virtually always
absent. One discovery that appears to be generic across all barrier islands is that
populations of spring peepers and other chorus frogs are nearly always absent.
A common denominator is that on the mainland these species breed in fish-free
ponds during winter rains. Summer is the wet period on the islands, so fish-free
ponds are seldom available during their breeding season. The absence of bullfrogs
on all barrier islands is unexplained but was first noted when Kiawah served as a
yardstick for comparative biodiversity.
Another notable phenomenon in which Kiawah reptiles and amphibians,
including frogs and toads, were among the main actors was support for the
theory of island biogeography. One aspect of the theory is that island size is one
determinant of the number of species inhabiting it. Smaller islands have fewer
Photo by JD Willson
first met the frogs of Kiawah Island more than 42 years ago. They are
Eastern spadefoot toad.
Naturally Kiawah