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The Salamanders Eurycea longicauda and Plethodon glutinosus in Gregorys Cave, TN: Monitoring and Observations on Ecology and Natural History
Nathan Taylor and Jonathan Mays

Southeastern Naturalist, Volume 5, Number 3 (2006): 435–442

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2006 SOUTHEASTERN NATURALIST 5(3):435–442 The Salamanders Eurycea longicauda and Plethodon glutinosus in Gregorys Cave, TN: Monitoring and Observations on Ecology and Natural History Nathan Taylor1,2,* and Jonathan Mays1,3 Abstract - Monthly surveys were conducted in Gregorys Cave, Great Smoky Mountains National Park, for one year using systematic, repeatable methods to quantify the distribution and abundance of the salamanders Eurycea longicauda and Plethodon glutinosus. Information was gathered regarding larval development of E. longicauda in cave pools, as well as the occurrence of young P. glutinosus. Salamanders were most commonly encountered during spring and late summer from the entrance gate to 50 m inside the cave. Both species were found deepest in the cave during late summer–early fall and late winter–early spring. Young P. glutinosus and recently transformed E. longicauda were observed during late winter and early spring between 50 and 80 m inside the cave. Additional study is required to further understand the timing and frequency of metamorphosis of larval E. longicauda in cave pools. Introduction Recent publications have addressed the need for information regarding the natural history and monitoring of plethodontid salamanders using caves and the rock-face habitats adjacent to cave openings (Dodd et al. 2001, Himes et al. 2004, Jensen and Whiles 2000, Jensen et al. 2002, Salvidio 2001). Due to the threat of local and worldwide amphibian declines (Blaustein et al. 1994, Kiesecker et al. 2001), there is a need for accurate natural history data and knowledge of population dynamics. Cave habitats are complex and present sampling challenges when attempting to detect and quantify cave inhabitants. Most cave walls are devoid of vegetation, but possess scattered cracks and fissures of varying size and orientation. These complex matrices of refugia complicate the use of traditional mark-recapture and temporary removal techniques for salamanders (Bailey et al. 2004). Population estimators have received little attention in cave systems, and as a result, visual encounter surveys have been used to gather data regarding the presence and abundance of cave-inhabiting salamanders (Dodd et al. 2001, Jensen et al. 2002). The purpose herein is to present the results of a 12-month survey using systematic, repeatable methods for quantifying Eurycea longicauda (Green) (Long-tailed Salamander) and Plethodon glutinosus (Green) (Northern Slimy Salamander) in Gregorys Cave, Great Smoky Mountains National Park (GSMNP). 1Department of Biology, Western Carolina University, Cullowhee, NC 28723. 2Current address - 2891 Old Charleston Road, Gilbert, SC 29054. 3Current address - 26 East Starnes Cove Road, Asheville, NC 28806. *Corresponding author - nathanieltaylor01@hotmail.com. 436 Southeastern Naturalist Vol. 5, No. 3 The surveys of Dodd et al. (2001) in Gregorys Cave, as part of the US Geological Survey’s Amphibian Research and Monitoring Initiative, revealed the presence of the above species and, until this report, represent the only in-depth study of these salamanders in the cave. Our objectives herein are to: 1) describe the observed distribution of salamanders within the cave over a 12-month period, 2) report on the presence of larval and recently transformed E. longicauda in and around rimstone pools, and 3) document encounters of young P. glutinosus in the cave. Methods Gregorys Cave is located in Blount County, TN on the north side of Cades Cove at the base of Cave Ridge. The entrance to the cave is southwest- facing at an elevation of 610 m. It is a small cave with just over 300 m of total passage length developed in Jonesboro limestone of the Knox group, Ordovician age. The cave contains several well-developed speleothems such as stalactites, stalagmites, flowstone, and a number of rimstone pools fed by ceiling drips (Barr 1961, Mays 2002, Wallace 1984). A gate installed at the cave entrance protects the cave from human disturbance. Sampling took place once each month for 12 consecutive months, starting in May 2000 and ending in April 2001. Only the main-trunk passage of Gregorys Cave was sampled. It was divided into 14 sections, each 10 m in length, from the gate to the back of the cave, excluding the smaller side passages. Section one began at the gate 5 m inside the cave entrance. Each individual section was subdivided into three sub-sections: north wall, floor, and south wall. Each member of the three-person survey crew, equipped with a Petzl Zoom headlamp with a standard 4.5-V bulb and a hand-held lantern light with a halogen 6.0-V bulb, was responsible for a different sub-section (i.e., one person surveyed the floor, while the other two surveyed the walls to a height of 3 m). The two surveyors responsible for the walls also surveyed the floor adjacent to the wall where they were stepping. Each observer intensively searched his/her assigned sub-section, taking care to investigate every fold and crevice. The identity, location (wall or floor), and distance into the cave from the entrance gate were recorded for each salamander. Survey effort (minutes spent surveying each 10-m section) and any noteworthy observations were also recorded. This procedure was repeated consecutively for each of the 14 sections. Animals were not captured and therefore neither measurements nor their sex were determined. Small P. glutinosus (estimated 25–30 mm snout-vent length [SVL]) were identified as second-year individuals based on the measurements reported in the literature (Hairston 1983, Highton 1962, Semlitsch 1980). Small E. longicauda (estimated 20–30 mm SVL) were considered recently transformed individuals (Ryan and Bruce 2000). Larger individuals of both species were categorized as sub-adults/adults and constituted individuals greater than two years old. Information was gathered throughout the study regarding the distribution 2006 N. Taylor and J. Mays 437 and abundance of E. longicauda larvae in cave pools. Plethodon glutinosus has direct development. The number of each species of salamander per category was totaled for each month. Results From May 2000 through April 2001, a total of 7656 search minutes (mean = 638 min per visit per three observers) during daylight hours were spent actively searching the 14 main-trunk sections of Gregorys Cave. A total of 15 P. glutinosus and 23 non-larval E. longicauda were encountered during the sampling period (Fig. 1). No other amphibians were observed inside the entrance gate. In general, salamander sightings were most numerous between August and October 2000 and in April 2001. During other months, no more than one individual of each species was observed. The subadult/ adult group of both species was not encountered during the period November 2000–January 2001. Eurycea longicauda were often seen within wall cracks; however, individuals were encountered at the edge of a rimstone pool in October 2000 and April 2001 and near a piece of wood on the floor in September 2000. Plethodon glutinosus were most often observed on the cave floor near the north or south wall. In September 2000, one relatively large individual was found under a rock within the first 10-m sub-section. Both species were most commonly observed Figure 1. Total number of Plethodon glutinosus and metamorphosed Eurycea longicauda observed in Gregorys Cave over the 12-month sampling period (May 2000–April 2001). 438 Southeastern Naturalist Vol. 5, No. 3 between the entrance gate and 50 m into the cave (Table 1). The farthest distance in the cave from the entrance gate that P. glutinosus were found was 70 to 80 m, including a second-year juvenile in March 2001 and an adult in April 2001. Observations of P. glutinosus ranged from the gate to 80 m (median = 20– 30 m) inside the cave. Eurycea longicauda were found further into the cave than P. glutinosus (the gate to 120 m, median = 40–50 m). Individuals were encountered at 90 to 100 m and 110 to 120 m in October 2000 and at 80 to 90 m and 100 to 110 m in April 2001. Eurycea longicauda larvae (estimated 8–12 mm SVL) were found in the cave pools 40–50 m and 80 m inside the cave. Larvae were observed in pools in June (n 􀂧 5) and July (n 􀂧 25) 2000 and again in March (n 􀂧 10) and April (n 􀂧 60) 2001; they were most abundant in pools between 40 and 50 m inside the cave. Eurycea larvae were probably underestimated because they are secretive and often take cover under the silt layer (Anderson and Martino 1966). Water levels in pools were at their lowest in September 2000 and at their highest in February and March 2001. Six of the 23 metamorphosed E. longicauda were considered first-year juveniles. Their estimated SVLs were between 20 and 30 mm (30–40 mm total length), a range consistent with other observations (Ryan and Bruce 2000). They were encountered only on the cave floor near pools between December 2000 and April 2001 and at distances from 40 to 80 m from the entrance gate. Of the 15 P. glutinosus observed, four individuals (estimated 25–30 mm SVL) were considered second-year juveniles (􀂧 1.5 years beyond hatching), based on measurements of young P. glutinosus after they emerged from their brood sites (Hairston 1983, Highton 1962, Semlitsch 1980). In Gregorys Cave, these four individuals were observed between January and April 2001 at distances from 30 to 80 m from the entrance gate. Two were found climbing at the top of different, large speleothem columns in the middle of the floor in March and April 2001. Table 1. Distances Plethodon glutinosus and metamorphosed Eurycea longicauda were observed (in 10 m intervals) in Gregorys Cave from the gated entrance over the 12-month sampling period (May 2000–April 2001). Distance (intervals) Plethodon glutinosus Eurycea longicauda from entrance (m) (# observed) (# observed) 0–10 3 2 10–20 2 3 20–30 5 4 30–40 1 4 40–50 2 2 50–60 - - 60–70 - 2 70–80 2 2 80–90 - 1 90–100 - 1 100–110 - 1 110–120 - 1 Total 15 23 2006 N. Taylor and J. Mays 439 Discussion Eurycea longicauda and P. glutinosus were found in Gregorys Cave from the twilight zone to near the end of the main-trunk passage. Our observations suggest that season affects the distribution and activity of the two species along the main passage and entrance. Late spring to midsummer (May–July) encounters were infrequent; salamanders were observed, on average, closer to the entrance than at any other time of the year. Activity peaked during late summer–early fall (August–October), when animals moved deeper into the cave. Sub-adult/adult salamanders were inactive in late autumn–winter (November–January), even though interior conditions remain relatively constant year-round. Activity increased in late winter–spring (February–April) as individuals presumably emerged from refugia relatively deep in the cave and moved closer to the cave entrance. Although our samples were small, this seasonal movement and activity is consistent with other cave studies which have found salamanders: 1) close to the entrance, but less active during summer; 2) more active in the fall with movement further inside the cave; 3) near inactive during winter despite favorable conditions; and 4) active in spring with movement from deeper in caves to nearer the entrance (Anderson and Martino 1966, Dodd et al. 2001, Hutchison 1958, Mohr 1944, Rudolph 1978). Both species of salamander were found deepest in the cave in October and April. We interpret this as indirect evidence of overwintering within Gregorys Cave. Dodd et al. (2001) concluded that salamanders did not overwinter in the cave. They did not observe deep-dwelling E. longicauda or P. glutinosus in their successive April samples and did not sample in October. We found four P. glutinosus and one E. longicauda during winter surveys. Camp and Jensen (2004) discovered a female P. glutinosus guarding a clutch of eggs in a cave in Georgia in late October. Mohr (1944) tracked Long-tailed Salamanders in an abandoned mine in Pennsylvania over a consecutive 12-month period. His highest counts and deepest records of this salamander were also in October, when individuals moved deep in the cave to overwinter, and in April, before they exited the cave later in the spring. Dodd et al. (2001) conducted 16 visual encounter surveys in Gregorys Cave. Five of those monthly samples (May–September 2000) overlapped with our surveys. For this period, the total numbers of the two species observed inside the entrance gate were nearly identical for both studies. During these months, both studies also reported similar numbers of E. longicauda larvae in cave pools. Dodd et al. (2001) found E. longicauda and P. glutinosus as far as 83.1 and 40.3 m into the cave from the entrance gate, respectively, whereas we found four salamanders of each species further inside the cave than their deepest records—some as much as 40 m deeper. Our ability to detect salamanders in the less productive zone deeper in the cave may have been aided by searching the cave in 10-m increments, because it refocused our search effort after each previous section. 440 Southeastern Naturalist Vol. 5, No. 3 We observed little salamander activity from November to January, due likely to the effects of season on visible activity. Our study and that of Dodd et al. (2001) indicate that April is an appropriate month to begin quantifying sub-adult/adult salamanders. Dodd et al. (2001) found the highest number of both species inside the cave in September. However, sampling should be continued beyond September, given that we encountered more E. longicauda in October than in any other month. The time of day chosen to search caves for salamanders likely affects observation probabilities. Hutchison (1958) and Rudolph (1978) found that cave-dwelling salamanders are more active at night. The low visible activity of salamanders observed during summer samples (Dodd et al. 2001 and the present study) may have been an effect of diurnal sampling. The fate of larval E. longicauda in Gregorys Cave pools deserves greater study. Dodd et al. (2001) felt that successful transformation of larvae was unlikely due to the scarcity of invertebrate prey in pools and the late-season drying of cave pools. However, Gregorys pools have been shown to support a variety of small invertebrates. Among the four main cave floor pools, Mays (2002) found an average of 25 amphipods or isopods during the same months that we observed E. longicauda larvae. This measure of prey availability is probably conservative because the pool substrate, where other prey items likely exist, was not disturbed during sampling. He also observed, but did not quantify, aquatic oligochaetes and flatworms, as well as drowned terrestrial invertebrates, in pools with larvae. The late-season drying of Gregorys pools may not constrain larval transformation. Larvae appear in late winter (March), when pool volume is normally high. During our study, cave pools filled from March to early spring and did not dry until late summer, a maximal period of approximately seven to eight months. Following hatching in late winter, the larval period of E. longicauda in Gregorys Cave is probably between four to seven months, as at other localities (Anderson and Martino 1966, Ireland 1974, Rudolph 1978, Ryan and Bruce 2000). The sizes of the small E. longicauda we encountered are consistent with estimates of growth and metamorphosis reported by these authors. If adequate precipitation fills cave pools in late winter–spring, larvae may complete metamorphosis and disperse from pools before they dry later in the year. Long-term surveys and cave-specific methodology will be required to gather data sufficient enough to assess changes in populations of these subterranean salamanders in Gregorys Cave. Further research might also explore the movements of salamanders between surface and underground habitats and resolve whether or not either species completes its entire life cycle within the cave. Intensive sampling of the cave’s pools must be avoided because the pools are sensitive microcosms that support amphipod crustaceans unique to this cave (Mays 2002). 2006 N. Taylor and J. Mays 441 Acknowledgments We thank David Beckett, Richard Bruce, and two anonymous reviewers for providing constructive comments on earlier drafts of this manuscript. The research was funded in part by Friends of the Smokies in a grant to J. Mays. Many individuals from GSMNP supplied valuable time and energy assisting us in our endeavors, most notably B. Nichols, and J. Pipenbring. Several people graciously donated their time and energies assisting in the field: R. Flowers, P. Jones, L. Maloof, M. Peterson, W. Reeves, J. Sanders, C. Singletary, and J. Vaughn. Special thanks to the reference librarians of the Lexington County, South Carolina Public Library for their willingness to fulfill numerous requests for journal articles via interlibrary loan. Literature Cited Anderson, J.D., and P.J. 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