Terrestrial Drift Fences with Pitfall Traps 



13 



Table 4. Annual and local variation in total captures of adult amphibian and 

 reptile species commonly sampled in drift fences on the Savannah River 

 Plant, South Carolina. Each sampling year began in September and 

 continued through August. 



Site and 





Sampling year 





species 



1978-79 



1979-80 



1980-81 



Rainbow Bay 









Notophthalmus vihdescens 



1,271 



1,058 



772 



Scaphiopus holbrooki 



51 



10 



45 



Rana utricular ia 



508 



346 



475 



Kinosternon subrubrum 



53 



24 



23 



Cnemidophorus sexlineatus 



1 



1 



3 



Tantilla coronata 



15 



28 



8 



Sun Bay 



Notophthalmus viridescens 

 Scaphiopus holbrooki 

 Rana utricularia 

 Kinosternon subrubrum 

 Cnemidophorus sexlineatus 

 Tantilla coronata 



1,757 

 1,271 



2,745 

 756 



728 

 12 



99* 



79 



35 



87* 



16 



19 



19* 



29 



12 



40* 



50 



10 



* Minimum estimate 



certain species of treefrogs (Hyla), which can climb the sides of a bucket 

 or a fence (Gibbons and Bennett 1974). For many large mammals (e. g. 

 raccoon, opossum), no adults have ever been captured in the traps. 

 However, those species for which the technique is either always or never 

 effective are not the primary problems. The major difficulty in interpre- 

 tation and analysis of data from drift fences results from those species 

 whose captures only partly reflect the numbers of individuals that actu- 

 ally encounter the fence or live in the vicinity. Unless the effectiveness or 

 sampling rate is known, certain conclusions relating to population size 

 or absolute abundance should be drawn with caution. However, the 

 potential for using the technique to estimate larval survivorship, immi- 

 gration and emigration rates, genetic exchange, and other difficult-to- 

 obtain data, has been demonstrated (Gibbons 1970; Shoop 1974; Gill 

 1978; Semlitsch and McMillan 1980; Semlitsch 1981) and should not be 

 underestimated. 



Merely revealing the presence of a rare species can be a contribu- 

 tion to an understanding of its basic biology. Star-nosed moles, Con- 

 dylura cristata, have been infrequently captured in pitfall traps on the 



