146 
J. Whitfield Gibbons and Julian R. Harrison III 
They are generally of low elevation and parallel the mainland, from 
which they are separated by salt marsh or, in some instances, by open 
water. Sand or gravel is the predominant soil texture. Most geologists 
consider the Atlantic barrier islands of the United States to be Holocene 
in origin, probably formed within the last 6,000 years. 
Several theories have been proposed to explain the origin of barrier 
islands. Among these, the emergence of offshore bars (Leont’yev and 
Nikiforov 1965; Otvos 1970), the submergence of coastal ridges (Hoyt 
1967, 1968), and the isolation of sandspits (Fisher 1968), have been the 
most prominent. The most appealing theory is that of Schwartz (1971) 
who compromised by suggesting that a combination and interaction of 
all three processes was the most suitable overall explanation. However, 
he indicated that one mode of development or another might be more 
prevalent in a particular situation or locality. 
On the southeastern Atlantic coast, those barrier islands with ocean- 
facing beaches and large enough to support terrestrial vertebrates have 
certain characteristics in common. Among these are a sand dune complex 
beginning above the high tide mark. The dune system is frequently mar- 
gined by a hardwood thicket of shrubs and trees stunted by continual salt 
spray. Plant communities of the island interiors are generally a combina- 
tion of hardwoods, palmettos and pines although the composition of a 
particular forest is the consequence of soil, climate, and recent historical 
events. One apparent characteristic of the southern barrier islands is that 
most woody species are evergreen. Fresh water may be abundant on some 
islands, absent on others. Even the largest freshwater lakes, however, 
have the potential of completely drying up during long periods of 
drought. Extensive salt marshes frequently make up the landward 
borders of the islands, which are then further separated from the main- 
land by brackish or salt water. This may take the form of tidal creeks or, 
in some cases, a major sound. 
A common threat to the ecological integrity of all barrier islands of the 
United States is the impact of development and other human activities 
(Dolan et al. 1973). Nonetheless, thorough studies of the flora and fauna 
of these unique habitats have lagged far behind those of other natural 
environments. The limited knowledge available about the reptiles and 
amphibians of the barrier islands of the Gulf and Atlantic coasts was 
compiled by Gibbons and Coker (1978). Despite the great abundance and 
diversity of reptiles and amphibians in the Southeast (Conant 1975; Mar- 
tof et al. 1980), a clear need exists for documentation of the ecology of 
these animals in the fast-disappearing natural habitats of barrier islands. 
The Study Areas 
The islands are located 19 km south (Kiawah) and 22 km north (Cap- 
ers) of Charleston (80‘^02'W, 32°54'N), Charleston County, South 
