1. The Fall Diet of Cave Salamanders (Eurycea lucifuga) from Pigeon Mountain Examined Using Non-Lethal Gastric Lavage Techniques
Jacob Hutton, Kate Donlon and William Ensign, Department of Ecology, Evolution and Organismal Biology
Introduction
Results
Discussion/Conclusions
A study examining gut contents of E. lucifuga from the entrances and twilight zones of central Tennessee and northern Alabama caves in spring and summer found 73 taxonomic representatives from 21 orders with Diptera comprising 60% of all prey items (Peck 1974).
A second study examining gut contents of E. lucifuga from caves in Alabama, Georgia, Kentucky, and Tennessee in the spring and summer found 111 taxonomic representatives from 23 orders, with Trichoptera (caddisfly) being most commonly consumed prey item followed by Diptera (Peck and Richardson 1976).
In the second study, Diptera comprised 49% of the diets of salamanders captured in the dark zone of caves, whereas those captured in the photic zone included 78% from Trichoptera-Plecoptera and 15% from Diptera (Peck and Richardson 1976).
In both studies, salamanders were sacrificed and the entire stomach and digestive tracts of each salamander were examined, whereas we non-lethally examined only the stomach contents during the fall.
Overall, we found less diversity in prey items than the previous studies. These differences are likely due to our smaller sample size and seasonal prey availability, although differences in sampling technique are also possible. Overall, we also found Diptera to be the most frequent prey item.
The E. lucifuga stomach contents in this study frequently had mucus coated boluses of non-prey items. Similar boluses have been observed in other studies (S. Peck, personal communication) and suggest that E. lucifuga has less than complete success in its’ attempts at prey capture.
The Cave Salamander, Eurycea lucifuga, is a lungless plethodontid salamander broadly distributed in the southeastern United States (Hutchison 1966; Petranka 1998; Fig. 1) and as the name implies, it is generally found around limestone caves and their springs (Hutchinson 1966).
Eurycea lucifuga life history is well documented (Organ 1968, Niemiller et al. 2009; Ringia and Lips 2007), but diet studies are limited (Peck and Richardson 1976; Peck 1974) and there is no information on fall diets.
This study investigates fall diets of E. lucifuga in northern Georgia caves.
26 adult E. lucifuga were captured but only 15 had prey items in their stomachs. A total of 31 prey items from five invertebrate orders were identified (Fig. 4).
8 individuals (42%) had flies (Diptera: Mycetophilidae, Dolichopodidae, Phoridae adults), 2 (11%) had beetles (Coleoptera: Cantharidae larvae), and 1 each (5%) had spiders (Araneae), harvestmen (Opiliones: Phalangodidae), mites (Acari: Laelapidae), while 6 (32%) had unidentified prey (Fig. 4).
Eleven of the 15 E. lucifuga stomachs contained identifiable prey items, four had multiple prey orders, and nine salamanders had only one prey item.
One individual had seven adult Dipterans (Mycetophilidae) and another had four Coleoptera larvae.
We found boluses containing only sand, small rocks, and detritus in 7 of the 15 salamanders. Peck (1974) found boluses with sand and other substrates 66 times in 52 E. lucifuga and Peck and Richardson (1976) found them 215 times in 213 salamanders.
Fig. 5. Tightly condensed Diptera
Fig. 4. Percent occurrence of prey items in adult Eurycea lucifuga from Pigeon Mountain, Ga.
Fig. 6. Diptera wings
Fig Range map of the Cave Salamander (Eurycea lucifuga), image borrowed from Lannoo (2005).
Methods
Acknowledgments
We analyzed the stomach contents of E. lucifuga from the cave entrances and twilight zones of Petty John’s cave and Screech Owl cave within the Crockford-Pigeon Mountain Wildlife Area in northwest Georgia.
Both caves were sampled beginning at dusk on a total of five occasions: 15, 17, 19, and 23 October 2015 and 3 November 2015.
Adult salamanders were capture and anesthetized according to Cecala et al. (2007).
Salamanders stomachs were flushed with PTFE tubing and syringes using methods described by Fraser (1976).
Stomach contents were placed in vials containing 70% ethanol, returned to the KSU lab, and identified to the lowest possible taxonomic level.
Fig. 9. Mucous bolus filled with substrate and organic matter
We thank Joseph Dirnberger for assistance with prey item identifications and Stewart B. Peck for his invaluable expertise on salamander stomach contents. We also would like to thank the Georgia DNR for allowing us to use their Crockford-Pigeon Mountain Wildlife Area Deer Check station for the stomach lavage.
Fig. 7. Larval Coleoptera head
Fig. 8. Larval Coleoptera
Literature Cited
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Hutchison, V.H Eurycea lucifuga. Pp. 24.1–24.2. Catalogue of American Amphibians and Reptiles. Society for the Study of Amphibians and Reptiles, St. Louis, Missouri.
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Fig. 2 Materials used in gastric lavage: Damp paper towel, BD 3/10 cc (30 units) syringe, dissecting probe, tweezers, Orajel, and 2 cuttings of 1.3 mm OD PTFE tubing.
Fig. 3. Image showing a smaller horizontal tube holding the mouth open and tongue up while a larger tube is extended into the oral cavity of E. lucifuga, note the projectile tongue that is partially extended with an attached prey item.