River Frog 7 5 



Much attention has been devoted in recent years to the apparent global 

 decline in many amphibian populations (Barinaga 1990; Blaustein and Wake 

 1990; Phillips 1990, 1995; Wyman 1990; Livermore 1992). No single cause 

 explains all of these widespread and often alarming disappearances, and there is 

 general agreement that a combination of factors is probably responsible. 

 Although habitat loss has been associated with the decline of many species, this 

 does not seem to be the case with the river frog in North Carolina; suitable habi- 

 tat appears to be plentiful. The fact that oxbow lakes on black water rivers are 

 rarer in North Carolina (Schafale and Weakley 1990) than in areas further south, 

 might represent a limit of prime breeding habitat for river frogs. However, the 

 species breeds in other habitats as well, and places where it has been taken his- 

 torically in the state do not seem unique in any way that is readily observable. 



Reasons for the apparent disappearance of the river frog from sites 

 where it once occurred are unknown and must remain speculative. Factors lim- 

 iting the distribution of the species are poorly known. The frog was apparently 

 never common or widespread in North Carolina, and small, scattered populations 

 of any species are usually more vulnerable to extinction than are large, wide- 

 spread ones. Species at the edge of their range likewise tend to be susceptible. 

 Some possible explanations for the apparent disappearance of R. heckscheri from 

 North Carolina, all of them speculative, include a number of diverse factors: 



1) Frog gigging or spearing still appears to be a popular sport in some parts of 

 southeastern North Carolina, although many persons encountered during the sur- 

 vey spoke of its being more widely practiced (as well as more productive) in past 

 years. The rather unwary adult river frogs (Carr 1940, Wright and Wright 1949, 

 Mount 1975) probably make easier targets for frog hunters than any other Rana 

 species. It is conceivable that intensive take by humans in an area could seri- 

 ously impact or eventually eliminate populations, especially those that were rel- 

 atively small. 



2) Other ranids surely compete with river frogs, both as larvae and adults, and 

 the niche of the bullfrog in particular seems to overlap that of the river frog rather 

 broadly (Carr 1940, Wright and Wright 1949). Although the two have been 

 taken sympatrically at numerous sites, the highly adaptable bullfrog is probably 

 a better competitor in certain, if not most, situations, and it is possible that a 

 change in environmental quality or in some particular selective pressure could 

 offer bullfrogs an advantage leading to river frog extirpation. 



3) A general overall decline in environmental quality could be responsible for 

 the river frog's decline in North Carolina. It was beyond the scope of this survey 

 to delineate the exact causes or effects of any environmental degradation that 

 may have occurred over the past several decades. Although precise long-term 

 data are difficult to obtain, it seems almost certain that some declines in water 

 quality have occurred in the state's blackwater rivers. Most fishermen and other 

 local residents encountered during the course of field work seemed of the opin- 



