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The diet of the cumberland plateau salamander (Plethodon kentucki) in an old growth forest of Southeastern Kentucky.

INTRODUCTION

Terrestrial lungless salamanders are known to reach very high densities in certain forested ecosystems of the United States (Bailey et al., 2004; Dodd and Dorazio, 2004) and can be an important component in the top down regulation of invertebrate populations (Davie and Welsh, 2004; Semlitsch et at., 2014). Wyman (1998) estimated a population of Plethodon cinereus in New York could consume 1.5 million prey items/ha/year. It is generally thought plethodontid salamanders are opportunist euryphagous predators and prey acquisition is typically only related to prey availability and microhabitat selection (Jaeger. 1981; but see Paluh et at., 2015).

Numerous studies have examined the diets of large (i.e., adult SVL > 4.0 cm) salamanders in the genus Plethodon (Oliver, 1967; Rubin, 1969; Whitaker and Rubin, 1971; Powders and Tietjen. 1974; Jensen and Whiles. 2000; Lewis et aL, 2014). However, the diets of 37% (20 of 54 extant species) of North American Plethodon salamanders are still entirely unknown (Duellman, 1954: Holman, 1955; Brandon, 1965; Oliver, 1967; Rubin, 1969; Whitaker and Rubin, 1971: Powders and Tietjen. 1974; Fraser, 1976a: Bailey, 1992; Mitchell el aL, 1996; Petranka, 1998). Furthermore, very few studies have identified prey items beyond the taxonomic level of order. Though prey information at the level of order can be useful, prey identified to more specific taxa can be used to identify changes in specific prey availability, to compare the relative importance of prey items between similar species and regions, and to gain knowledge of taxon-specific feeding behaviors.

The Cumberland Plateau Salamander [Plethodon kentucki (Mittleman)] is a large terrestrial lungless salamander confined to the Cumberland Plateau of the central Appalachian Mountains (Mittleman, 1951; Highton and MacGregor, 1983). Bailey (1992) examined the diet of P. kentucki in West Virginia and identified prey to the level of order. In this study we examined the diet of adult P. kentucki from an old growth forest in southeastern Kentucky in order to evaluate the overall importance of prey groups to this regionally endemic species.

Methods

We analyzed stomach contents of adult P. kentucki (4.0 cm or greater; Mittleman, 1951) and excluded juvenile salamanders due to possible ontogenetic differences in prey composition. We collected salamanders over a 75 m sampling transect on a ridgetop (locally known as Whitaker Branch, 37[degrees]5'16.73"N, 82[degrees]59'16.99"W) within the forest of Eastern Kentucky University's Tilley Cornett Woods Appalachian Ecological Research Station (LCW), Letcher County, Kentucky. The study area is an upland old growth mixed mesophytic forest at 340 in elevation (Braun. 1950; Martin. 1975). The forest primarily consists of lire Eastern Hemlock (Tsuga canadensis) stands, with mixed oak (Quercus sp.), and American beech (Fagus grandifolia). See Martin and Shepherd (1973) and Martin (1975) for a complete list of vegetation at the study site.

We located salamanders by overturning rocks, logs, other cover objects, and sifting through dense leaf litter. Sampling was conducted during the early mornings and early evenings over eight samplings from 26 Apr. to 27 May 2016. Salamanders were placed in plastic bags with a moistened paper towel and transported to the research laboratory at LCW. All salamanders tvere anesthetized in a solution of 1g Maximum Strength Orajel[R]/1 liter of aged tap water (Cecala et al., 2007) and were removed from the anesthetic solution upon failure to right themselves after being flipped over. First, using a caliper, we measured snout-vent length (SVL: from the tip of the snout to the posterior angle of the vent) to the nearest millimeter. We then inserted an approximately 6.0 cm long piece of 1.3 mm OD PTFE tubing (Zeus Inc., catalog number AWG24) into the salamander's esophagus until there was resistance. Aged tap water was then pumped into the tubing using Nipro 3 ml. syringes with 22 gauge needles. Pumping was repeated until all food items had been removed (Fraser, 1976a). We placed salamanders in a recovery container of aged tap water and returned them to their approximate location of capture within 2.5 h. Immediately after removal, we identified stomach contents to the lowest possible taxonomic level and placed prey items into labeled vials containing 70% ethanol. Vials are stored in the Branson Museum collection at Eastern Kentucky University, Richmond, Kentucky.

Prey items were identified to order and in some cases family, genus, and species. In order to evaluate the overall importance of the stomach contents, prey groups are recorded with percent occurrence (the percentage of salamanders that ate a prey group) and percent abundance or percent total (the total number of prey items in a specific group divided by all prey items; adapted from Felix and Pauley, 2006). Empty stomachs were not included in percent analyses.

Results

We stomach flushed 73 adult P. kentucki (mean [+ or -] SE SVL = 5.9 [+ or -] 0.319 cm; range = 4.1-7.9 cm). Fifteen individuals had prominent mental glands (males), two individuals were gravid females, and 56 individuals were of unknown sex. Seventy-one of 73 individuals contained at least one prey item in their stomachs. We recovered 763 prey items. Salamander stomachs contained an average of 10.75 prey items of 58 prey types from 20 invertebrate orders (Table I; Fig. 1). Forty-two prey types were identified to the level of family or genus (Table 2). The four most important prey taxa accounted for nearly 75% of all prey items: Formicidae (ants), Araneae (spiders), Coleoptera (beetles), and Collembola (springtails) (Table 1: Fig. 1).

The diversity of ants found in the stomachs of P. kentucki was greater than all other prey types that could be identified to family or genus. Individuals were identified to four subfamilies and 12 genera (Table 2). Salamanders fed on each ant species in similar quantities throughout the sampling period, suggesting there were no changes in prey availability. However, 70% of the salamanders that fed on ants consumed individuals belonging to the genus Pheidole. Spiders appeared to be important prey; unfortunately, many could not be identified due to advanced digestion or method-based damage. Of those spiders that could be identified, members of the families Theridiidae (cobweb weavers) and Thomisidae (crab spiders) were the most common. The diversity of coleopterans was second to that of ants--nine families were identified. Nearly 70% of the beetles were adults, but adults and larvae were each found in 50% of the salamanders that ate coleopterans. Adults from the families Scarabaeidae (scarab beetles) and Curculionidae (true weevils) were the most frequently consumed coleopterans. Collembolans were identified to three families from three orders: individuals from Poduromorpha (Hypogastruridae) were (he least common, and members from Symphypleona (Sminlhuridae: globular springtails) and Entomobryomorpha (Isotomidae: smooth springtails) were more common and had similar abundances and frequencies. Micro-gastropods (Stvlommatophora) were found in nearly 25% of the salamander stomachs, suggesting land snails were an important component of salamander diets. The diversity of land snails was fairly large with eight species from six genera. Snails from the genera Glyphyalinia and Yentridens were the most frequently consumed. Among salamander stomachs containing dipterans, adult flies occurred in more than 80% and larva occurred in 30%. Overall, larval prey from three orders (Coleoptera, Dipt era, and Lepidoptera) made up approximately 6% of all food items.

Discussion

Ants have been reported as the most important prey group in many eastern North American Plethodon salamanders: P. albagula (Oliver, 1967; Milanovich et al, 2008), P. ampins (Rubin, 1969), P. cinereus (Cochran, 1911; Bellocq et al, 2000), P. cylindraceus (Fraser, 1976b), P. electromoiphosis (Duellman, 1954), P. glutinosus (Powders and Tietjen, 1974; Bailey, 1992; Jensen and Whiles, 2000; Hutton, pers. obs.), P grobmani (Brandon, 1965), P. jordani (Powders and Tietjen, 1974), P. kentucki (Bailey, 1992), P. metcalfi (Whitaker and Rubin, 1971), P. petraeus (Jensen and Whiles, 2000), P. richmondi (Hutton, pers. obs.), P. shermani (Whitaker and Rubin, 1971; Lewis et al, 2014), and P. wehrlei (Hall, 1976; Pauley, 1978). Here, we report that ants were the most important prey item of P. kentucki in southeastern Kentucky, in terms of both the percent of salamanders that consumed them and the total number of prey items. However, only a few Plethodon salamander diet studies have identified ants or other prey to family or genus or provided specific life stage information. Lewis et al (2014) found ten distinct ant taxa in the stomachs of P. shermani from North Carolina, with Aphaenogaster fulva and A. rudis most common. Paluh et al (2015) found A. picea in to be the most abundant ant in the stomachs of P. cinereus from Ohio. In P. kentucki stomachs, we found Aphaenogaster sp. to only comprise a fraction of total ant diversity (Table 2), with the majority of individuals belonging to the genus Pheidole. Sympatric Plethodon richmondi and P. glutinosus that were also sampled in our study area, both consumed a large diversity of ant genera, the majority of which were also Pheidole (Hutton, pers. obs.). Therefore, a regional or microhabitat difference may be responsible for the observed differences in the relative ant species composition and abundances within Plethodon stomach contents.

Similarly to the P. kentucki in our study, coleopterans from the families Scarabidae and Carabidae (ground beetles) were among the most frequent in the diet of P. albagula from Arkansas (Milanovich et al., 2008). In P. shermani stomach contents, Carabidae and Curculionidae were the most frequently observed families and were followed by individuals from the family Elateridae (click beetles; Lewis et al., 2014). In P. ampins from North Carolina, Rubin (1969) found individuals from Curculionidae and Carabidae to comprise the majority of the coleopteran diet. However, unlike in our P. kentucki, the previous studies noted adult coleopterans were more frequent and numerous than larvae, suggesting larvae may be more important to the P. kentucki in our study than to the other species.

Lewis et al. (2014) identified spiders in die stomach contents of P. shermani to five families, individuals from the family Linyphiidae (sheet weavers) were most common. Saldcid (jumping spiders) spiders were also present in their diet, similarly to the P. kentucki in our study (Lewis et al., 2014). Oliver (1967) found larval dipterans from two families (Blephariceraddae and Stratiomyidae) in the diet of P. albagula. Whitaker and Rubin (1971) also found larval dipterans more frequently than adult individuals in both P. metcalfi and P. shermani. Additionally, Jensen and Whiles (2000) also reported larval dipterans more frequently than adults in both P. petraeus and P. glutinosus. In our study however, larval flies were less important than adults, which could be attributed to seasonal differences but further investigation is needed.

The most important prey items found in P. kentucki from West Virginia (listed in order of importance) were ants, coleopterans, micro-gastropods, spiders, pseudoscorpions, collembolans, mites, and dipterans (Bailey, 1992). Bailey (1992) found prey from 18 orders but did not include life stages of prey items and sampling periods were not included in the methods. Therefore, we are unable make any comparisons beyond die order level or explore the influences of seasonality on prey composition. In West Virginia, micro-gastropods, pseudoscorpions, and diplopodans were eaten more frequently than in southeastern Kentucky (Bailev, 1992). Conversely, coleopterans, spiders, and collembolans were found in more individuals from Kentucky than West Virginia. Despite these differences, individuals from southeastern Kentucky and West Virginia appear to have generally similar diets.

Plethodon kentucki is a euryphagous salamander that consumes a wide diversity of ants, spiders, beetles, and micro-gastropods. To our knowledge, this is the fourth study to nonlethally examine the diet of a large terrestrial plethodontid; Fraser (1976a; h) and Lewis el at. (2014) were the first investigations. Future studies should nonlethally examine salamander diet across their known ranges and sample through the various seasons in order to better understand the mechanisms behind prey acquisition, composition, and possible selection. Invertebrates should also be collected in order to compare total community diversity and abundance with salamander stomach contents. Lastly, species level dietary information should be gathered to compare sympatric salamander prey selection and composition.

Acknowledgments.--This is contribution No. 46 of Lilley Cornett Woods Appalachian Ecological Research Station, Eastern Kentucky University. We thank J. Alex Baecher for help with sampling and Daniel Douglas for assistance on micro-gastropod identification. We would also like to thank Robert Watts and Curtis Cox for their invaluable knowledge of Lilley Cornett Woods and the surrounding forest. Lastly, we would like to thank the Division of Natural Areas (EKU) for funding this research and providing field station access. Research was performed under the Eastern Kentucky University Institutional Animal Care and Use Committee protocol No. 05-2015 and Kentucky Department of Fish and Wildlife Resources permit No. SC 1611150.

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--and C. Shepherd. 1973. Trees and shrubs of Lilley Cornett Woods, Letcher County, Kentucky. Castanea, 1973:327-335.

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JACOB M. HUTTON (1), Department of Forestry-, University of Kentucky, Lexington, Kentucky 40506; STEVEN J. PRICE, Department of Forestry, University of Kentucky, Lexington, Kentucky 40506; and STEPHEN C. RICHTER, Department of Biological Sciences and Division of Natural Areas, Eastern Kentucky University, Richmond, Kentucky 40475. Submitted 13 September 2016; accepted 13 December 2016.

(1) Corresponding author: e-mail: jakehutton@uky.edu, jakemhuttonl@gmail.com

Caption: Fig. 1.--Prey categories found in adult Plethodon kentucki (n = 73), expressed as percent occurrence and percent of total diet, from southeastern Kentucky from Apr.-May 2016
Table 1.--Prey types and frequencies in the stomachs of adult
Plethodon kentucki (n = 73) from southeastern Kentucky from
Apr.-May 2016

Prey category            Occurrence (%)   Total items (%)

Hymenoptera
  Formicidae                 73.24             44.04
  Araneae                    61.97             10.35
  Coleoptera                 57.75             9.96
  Coilembola                 42.25             10.22
  Diptera                    28.17             3.41
  Acari                      26.76             4.19
  Gastropoda                 23.94             2.75
  Lepidoptera (Larvae)       18.31             1.83
Chilopoda
  Geophilomorpha             16.90             1.97
  Oligochaeta                15.49             2.10
  Opiliones                  12.68             1.18
  Diplopoda                  11.27             1.31
  Pseudoscorpiones            8.45             0.92
Blattodea
  Isoptera                    4.23             0.66
Orthoptera
  Gryllidae                   2.82             0.26
Blattodea
  Blattidae                   1.41             0.13
  Isopoda                     1.41             0.13
  Ephemeroptera               1.41             0.13
  Empty stomach               2.82              --
  Unidentifiable prey        32.39             4.46

Table 2.--Prey types found in the stomachs of adult Plethodon
kentucki identified beyond the level of order and their percent
occurrence and makeup with each group, from southeastern
Kentucky from April-May 2016

                               Occurrence   Total items
Prey category                     (%)           (%)

Araneae
  Unidentified Spider            81.82         70.89
  Theridiidae                    25.00         16.46
  Thomisidae                      9.09         7.59
  Xysticus sp.                    2.27         3.80
  Salticidae                      2.27         1.27
Coleoptera
  Unidentified Larvae            46.34         30.26
  Unidentified Adult             24.39         14.47
  Scarabaeidae                   17.07         18.42
  Curculionidae                  17.07         9.21
  (Carabidae                      7.32         6.58
  Staphylinidae                   7.32         3.95
  Tenebrionidae                   7.32         9.21
  Silphidae                       4.88         2.63
  Elateridae                      2.44         1.32
  Elateridae Larvae               2.44         1.32
  Dytiscidae                      2.44         1.32
  Nitiulidae                      2.44         1.32
Collenibola
  Sminthuridae                   46.67         29.49
  Isotomidae                     40.00         33.33
  Unidentified Collenibola       40.00         25.64
  Hypogastruridae                13.33         11.54
Diptera
  Unidentified Adult             80.00         65.38
  Unidentified Larvae            30.00         30.77
  Tabanidae                       5.00         3.85
Formicidae
  Pheidole sp.                   71.15         43.45
  Unidentified Formicidae        42.31         12.80
  A mblyopone sp.                15.38         2.68
  Fasius sp.                     13.46         24.40
  Camponotus sp.                  9.62         1.49
  Formica sp.                     7.69         5.95
  Aphaenogaster sp.               7.69         1.79
  Temnothorax sp.                 5.77         5.06
  Myrmecina americana             5.77         0.89
  Stenamma sp.                    1.92         0.60
  Hypoponera sp.                  1.92         0.30
  Ponera pen nsylvanica           1.92         0.30
  Pyramica sp.                    1.92         0.30
Gastropoda
  Unidentified Snail             52.94         47.62
  Glyphyalinia indentata         17.65         14.29
  Ventridens suppressus          11.76         9.52
  Discus sp.                      5.88         4.76
  Glyphyalinia sp.                5.88         4.76
  Polygyridae sp.                 5.88         4.76
  Punctum minutissimum            5.88         4.76
  Strobilops labytrinthicus       5.88         4.76
  Ventridens sp.                  5.88         4.76
Isoptera
  Rhinotermitidae                  --           --
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Title Annotation:Notes and Discussion Piece
Author:Hutton, Jacob M.; Price, Steven J.; Richter, Stephen C.
Publication:The American Midland Naturalist
Article Type:Report
Geographic Code:1U6KY
Date:Jul 1, 2017
Words:3347
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