THE CAVE ASSOCIATED AMPHIBIANS OF GREAT SMOKY MOUNTAINS NATIONAL PARK

C. Kenneth Dodd, Jr., Marian L. Griffey, and Jeffrey Corser

Abstract: We surveyed all passages in Gregory's Cave, Great Smoky Mountains National Park, 16 times from 1998 to 2000 as part of an amphibian inventory and monitoring program. Standardized visual encounter techniques were used. Three species of salamanders and five species of frogs were observed, but only the Long-tailed Salamander and the Northern Slimy Salamander were observed beyond the twilight zone (to 45 and 87 m from the opening, respectively). Counts varied annually and monthly, with the majority of individuals being observed in April and from late summer to autumn. Larval Long-tailed Salamanders probably rarely complete metamorphosis because of limited food supplies and desiccation of breeding pools. We visited all other limestone caves within the park in addition to surveys in Gregory's Cave. The Cave Salamander and the Southern Zigzag Salamander are found only in localized, restricted habitats, that is, in caves and in limestone sinks; both are absent from Cades Cove. We provide a summary of unpublished and new occurrence records for cave-associated amphibians within the Great Smokies. Counts by themselves probably have little value in monitoring cave populations of salamanders. However,  visual encounter surveys might be useful in interpreting behavior, understanding factors affecting habitat use, and in detecting trends in cave-inhabiting amphibians when used in conjunction with species richness indices over a much larger area. Biologists and resource managers must take a regional approach in order to detect trends and to monitor the status of amphibian habitat specialists, especially cave-inhabiting salamanders.

METHODS

Surveys at Gregory's Cave

     We surveyed the amphibians in Gregory's Cave (35^o36'38" N, 83^o48'20" W), located on the southwestern slope of Cave Ridge (a spur of Tater Ridge) on the north side of Cades Cove, Blount County, Tennessee, beginning in July 1998. Gregory's Cave is a generally straight tunnel in Lower Ordovician dolomite of the Knox Group (Barr, 1961). At one time, the cave was operated commercially and was the location of social gatherings in Cades Cove, but an iron gate now limits access to the main cave in order to protect sensitive fauna and formations. The cave has a nearly level floor and ceiling, and its vertical walls average five meters in height. The total length is ca. 133 m, and the passage varies from six to 17 m in width. A low passage extends to the south for 37 m about two-thirds of the way into the cave. Numerous stalactites, stalagmites, columns, and rimstone pools, but no running water, are found within the cave passages.  Horizontal bedding results in horizontal cracks along the walls, whereas columnar formations have a great number of vertical folds offering ideal salamander hiding places. During periods of high water, pools may completely block the passage 40 m from the gate; additional pools are located ca. 60 and 75 m from the gate, but do not completely block the passage. During dry periods, especially in late summer and autumn, floor pools dry or become very low, and rimstone pools dry completely.

     Gregory's Cave was surveyed 16 times (Jul-Sep 1998; Apr-Sep 1999; Apr-Sep 2000; Dec, 2000). The area between the cave entrance and the gate located five meters inside the cave was thoroughly searched, including the leaf litter in the entranceway and within the cracks and crevices on the ceiling, floor, and walls. We used MagLite® torches were used to illuminate crevices. Survey effort was recorded (number of observers x total time searched), and air temperature, substrate temperature, and relative humidity were taken at the gate with an Atkins® model 39658-K digital thermometer and a Nester Instruments® RH pen. After opening the gate, we began the main cave survey following the same general procedures. Usually, one or two people surveyed each side of the passageway moving slowly and carefully to search all surfaces and crevices. Air temperature, substrate temperature, water temperature, and relative humidity were recorded at a small rimstone pool on the west side of the passage at ca. 75 m into the cave. The cave was surveyed until it terminated in a dome. Total survey time since entering the cave at the gate was recorded, and the furthest distance each species of salamander was observed was measured from the gate using a 100-m tape.

Additional Cave Surveys

     The location of caves within the Great Smoky Mountains National Park and associated Foothills Parkway right-of-way was obtained data from the National Park Service. Locations of the caves mentioned below, except for Gregory's Cave and Bull Cave which are shown on USGS topographic maps, are not provided because of the need to protect their sensitive faunas; persons interested in knowing these locations should contact the Twin Creeks Natural Resource Center of GSMNP. Caves, all of the Ordovician Knox Group, are found in four areas of the park: Cades Cove, Rich Mountain, Whiteoak Sink, and on the northwest slope of Cove Mountain along the Foothills Parkway right-of-way. Each cave was visited once or twice using the same general survey procedures as at Gregory's Cave; pit caves were not entered. Surveys of the area surrounding entrances, using time-constraint visual encounter techniques, determined which salamanders occurred on the surface near caves. Surface debris and leaf litter were turned for a period of 30-min, and the survey effort (number of observers  x time surveyed), species and life stage (adult, juvenile) were noted. Substrate temperature, air temperature, and relative humidity were recorded as above.

RESULTS

GREGORY'S CAVE

Sampling Effort and Environment. - A total of 4480 survey-minutes ( = 280 per visit) was spent surveying the entrance and passages of Gregory's Cave. Surveys were carried out between 09:00 and 13:30 hrs. Air temperatures (13-16^oC, = 13^oC), substrate temperatures (11-16^oC, = 13^oC), and relative humidity (48-74%, = 61%) outside the gate varied little except for December, when the temperatures were cold (air = 0^oC, substrate = 5^oC; values not included in means above). Air temperature (12-15^oC, = 14^oC), substrate temperature (12-14^oC, = 14^oC), water temperature (12-14^oC, = 14^oC), and relative humidity (60-80%, = 75%) did not vary greatly among sampling periods inside the cave 75 m from the gate, including the December 2000 survey when the ambient temperatures outside the cave were well below freezing.

Species Encountered. - Three species of salamanders were observed at the entrance and in the passages of Gregory's Cave: the Long-tailed Salamander (Eurycea longicauda), the Northern Slimy Salamander (Plethodon glutinosus), and the Blue Ridge Two-lined Salamander (Eurycea wilderae). Only one Blue Ridge Two-lined Salamander was observed, on 22 September 1998, at nine meters inside the gate. Five species of frogs were observed: the American Toad (Bufo americanus), Fowler's Toad (B. fowleri), Wood Frog (Rana sylvatica), Pickerel Frog (R. palustris), and Northern Green Frog (R. clamitans). All the frogs, with one exception, were counted at the entranceway before the gate, usually in the litter on the slope just inside the cave opening. A single adult male B. americanus was observed 10 m inside the gate, but still in the twilight zone, on 20 September 1999.

Almost equal numbers of the two most frequently observed salamanders were counted during the overall survey. Both adults and subadults were seen. In addition, larvae of the Long-tailed Salamander were also observed from April to September. Larvae were seen primarily in rimstone pools (usually one to four larvae per pool) formed on the side of a very large dome-like formation ca. 45-50 m from the gate, and in the first main cave pool (ca 40 m from gate). Most larvae were extremely small (ca. 10-15 mm total length), although two larvae collected in a pool 60 m from the gate on 7 September 2000 had lost most of their gills and were in the process of transforming. However, few larvae transformed because the rimstone pools and the main pool 40 m from the gate, locations where most of the larvae were seen, dried well before September in two of the three years of observation. The farthest in the cave that an E. longicauda larva was recorded was the observation of a single larva in a pool 73 m from the gate. The farthest in the cave from the gate that adult E. longicauda were observed was 83.1 m (8.2-83.1 m, = 58.7 m), whereas adult P. glutinosus did not seem to penetrate as far (2.0-40.3 m, = 26.5 m). Both maximum distances are beyond the cave's twilight zone.

Plethodon glutinosus was found around the entrance and just inside the opening of the cave during every month surveyed, even in December. They were inside the cave only during the warmest and driest months, except in December. Likewise, E. longicauda was seen in all the warmer months around the cave's opening; they were never observed inside the gate in May and June. Sightings were highest in April and from August to September inside the cave. All frogs were observed from June to September. The most frogs seen on a single survey was three: one R. clamitans and two B. fowleri on 10 July 2000.

Nine Southern Red-backed Salamanders (Plethodon serratus) and a single P. glutinosus were recorded during time constraint surface surveys around the entrance to Gregory's Cave (180 survey-minutes sampling effort) in April and May 1999. In addition, Eastern Wormsnakes (Carphophis amoenus) were also common (four captured in 30 minute survey on 7 May 1999, including two gravid females) under rocks on the surrounding hillside. A Black Ratsnake (Elaphe obsoleta) and a juvenile Copperhead (Agkistrodon contortrix) each were seen on separate occasions at the entrance to the cave.

Other GSMNP Caves

Myhr's Cave (Wear Cove): Two Cave Salamanders (Eurycea lucifuga) were found while surveying Myhr's (Stupka's) Cave on 9 June1998 (120 survey-minutes). We again surveyed Myhr's Cave on 10 May 1999 (90 survey-minutes), and found one E. lucifuga (a gravid female) inside the cave, five E. lucifuga and one E. longicauda in the rock crevices surrounding the entrance, and one Notophthalmus viridescens eft in the leaf litter near the entrance. This is a short cave with a stream at the end on the south side of Wear Cove on National Park Service property. Wallace (1984) reported the following species from this cave: P. glutinosus, E. longicauda, E. lucifuga.

Bull Cave (Rich Mountain): (35^o38'39"N, 83^o48'27"W): Bull Cave, an extremely deep and hazardous series of vertical drops located in a deep uvala on Rich Mountain (Barr, 1961), was never entered. However, we found Plethodon ventralis (Southern Zigzag Salamander) near the entrance in 1998, 1999, and 2000. The salamanders Plethodon glutinosus, P. serratus, Desmognathus conanti, E. wilderae, and N. viridescens were observed in three time constraint surveys around the entrances of Bull and the two Calf caves.

Calf Caves (Rich Mountain): Calf Cave #1 was entered briefly on 10 May 1999. One P. glutinosus and one Eurycea (possibly E. lucifuga) were seen at the entrance, but none inside the cave. A USGS field crew searched this cave on 22 August 2000 and found an adult P. glutinosus. Wallace (1984) reported P. glutinosus, E. lucifuga from these two caves.

Whiteoak Saltpeter Cave (Whiteoak Sink): Surveys of the entrance, entrance room, and surrounding rock faces on 6 May 1999 did not reveal any salamanders.

Rainbow Falls Cave (Whiteoak Sink): Surveys of the entrance room of Rainbow Falls Cave on 6 May1999, produced only a single P. glutinosus. A USGS field crew (JB, KS) captured a larval Gyrinophilus porphyriticus in the entryway on 22 August 2000. Wallace (1984) reported Desmognathus quadramaculatus at the entrance stream.

Blowhole Cave (Whiteoak Sink): The entrance to Blowhole Cave is a deep pit which is gated (Barr, 1961). We did not enter the cave, but an adult E. lucifuga was found in the rock crevices above the entrance in May 1999 by JDC. This appears to be the first record for this species from Whiteoak Sink. Terrestrial time constraint surveys documented P. glutinosus, P. serratus, P. ventralis, D. conanti, E. wilderae, Pseudotriton ruber, and N. viridescens in the vicinity of caves in the Whiteoak Sink. Wallace (1984) reported P. glutinosus, E. wilderae, Pseudotriton ruber, D. conanti, and G. porphyriticus from this cave.

Tory Shields Bluff Cave (Cades Cove): No salamanders were seen during a brief visit to the entrance of this small cave. A Milksnake (Lampropeltis triangulum) was observed in a nearby crevice. Wallace (1984) reported the following species from this cave: P. glutinosus, E. longicauda.

E. longicauda in Gregory's Cave

DISCUSSION

     All of the amphibians seen in the caves of the GSMNP have been observed in caves elsewhere. We verified the unpublished observations concerning the absence of E. lucifuga in Cades Cove, the presence of E. lucifuga at the Calf caves, and the co-occurrence of E. longicauda and E. lucifuga at Myhr's Cave. We provided the first records for the Cave Salamander in Whiteoak Sink. Cades Cove is an isolated valley drained by westward flowing Abrams Creek. Both Rich Mountain and Whiteoak Sink are geologically connected with Tuckaleechee Cove to the north, and Myhr's Cave is in Wear Cove, also to the north of the park boundary. These latter three locations are in limestone that is hydrologically and geologically isolated from Cades Cove. Hence, it is not surprising that neither the Cave Salamander nor the Zigzag Salamander are found within the cove despite the presence of limestone.

     Although not a cave-dwelling salamander, the Southern Zigzag Salamander (Plethodon ventralis) is a limestone associate elsewhere in its range. It is only found in the dolomite basins at the Bull Cave uvala and in Whiteoak Sink in GSMNP, and it does not appear to have crossed Rich Mountain and entered Cades Cove. After conducting hundreds of time constraint surveys throughout the park, including areas along the northern park border (on Rich Mountain, Cades Cove Mountain, Cove Mountain), we have not found P. ventralis at any other location. Contrary to previous reports, the Southern Zigzag Salamander does not occur at the Sinks or in the Sugarlands area.

     Salamanders use both the entranceway, where twilight penetrates, as well as deeper portions of the cave's stable environment. Eurycea longicauda is present around the entrance and in the interior in the spring, but during May and June salamanders apparently disperse from the interior of the cave and preferentially use the entrance and presumably surrounding terrestrial habitats; they return to the cave in late summer to autumn. The Northern Slimy Salamander can usually be found around entrances and in the bright twilight zone year round, but not until later in the season does it move deep into the cave. Salamanders do not seem to overwinter within the passages of Gregory's Cave, although we have only one mid-winter sample.

     Frogs appear to be occasional visitors to the cave entrance, where invertebrates are abundant and humidity is high. They were always found just within the entrance where the air was cool and the light levels low. Most observations occurred in the latter part of the sampling season, presumably as frogs settled in to their non-reproductive season home ranges. Early in the year, it is likely that most individuals were away from the hillsides at breeding ponds. Caves may serve as temporary refuges from adverse surface conditions.

SOUTHEASTERN AMPHIBIAN RESEARCH AND MONITORING INITIATIVE, FLORIDA INTEGRATED SCIENCE CENTER, U.S. GEOLOGICAL SURVEY
7920 N.W. 71^ST STREET, GAINESVILLE, FLORIDA 32653