Salamander Populations 



61 



(Hairston 1987). There are several known causes for the fluctuations, 

 which occurred over much shorter intervals than the mean generation 

 times (5-10 years) for the different species (Hairston 1987). Some 

 were due to cold weather, when Plethodon tend to remain underground 

 (first class, September 1981); others were due to exceptionally 

 enthusiastic classes (September 1977). None of the fluctuations in 

 numbers observed can be attributed to a real change in the number 

 of salamanders actually present. The mean generation time for P. 

 jordani is 9.8 years and for glutinosus it is at least a year longer 

 (Hairston 1987). Thus, fluctuations in numbers seen at shorter intervals 

 do not represent real changes. 



iocv 



P jordoni 



Fig. 1. Population history of Plethodon jordani and P. glutinosus in the 

 Heintooga locality, as shown in numbers observed by successive classes from 

 1976 to 1990. Broken lines represent preliminary observations not exactly 

 equivalent to class date. Arrows show means of all class data; standard 

 error not given because the counts might not be independent because of the 

 longevity of individual salamanders and the likelihood that at least some of 

 the same ones were observed on successive class exercises. 



