Use of twilight zones of caves by plethodontid salamanders

We studied the use of six caves by metamorphosed plethodontid salamanders from 2000-2005 in the Cumberland Plateau of northwestern Georgia. Nine species were observed, the most abundant being, in descending order, Eurycea lucifuga, Plethodon glutinosus, P. petraeus, and E. longicauda. Eurycea lucifuga and P. glutinosus were the only species observed in all six caves. Salamanders used caves seasonally, and all four species were more abundant within caves during seasons with warm, long days. A parsimonious explanation for the observed seasonal pattern of cave use is that salamanders use both cave and surface habitats, moving into caves to avoid hot, dry conditions on the surface. Eurycea lucifuga was most abundant in low-elevation, cold caves. The abundance of P. glutinosus was positively related to cave dimension and secondarily to wall heterogeneity. Species richness was not randomly distributed among caves, but neither was it consistently related to particular variables. Caves into which salamanders crowd during certain seasons represent ideal situations for the testing of hypotheses related to species interactions, both within and among species.