Short Communication |
Corresponding author: Ryan M. Jones ( rjones@cambrianenvironmental.com ) Academic editor: Enrico Lunghi
© 2024 Ryan M. Jones, Zachary C. Adcock, Andrew R. MacLaren, Kemble White IV.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Jones RM, Adcock ZC, MacLaren AR, White IV K (2024) A modified trap design for sampling subterranean habitats for central Texas Eurycea salamanders. Subterranean Biology 50: 53-64. https://doi.org/10.3897/subtbiol.50.136402
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In this paper, we describe modifications to a sampling technique for surface, stream-dwelling salamanders for use in subterranean settings. Leaf litter bags are an effective and commonly used trap for salamanders, and their construction purposefully allows animals to move freely in and out of the trap. However, this presents a problem in subterranean deployment because retrieving the trap over long vertical distances, such as well sampling, allows time and space for the animals to escape. To overcome this challenge, we enclosed a leaf litter bag in a suspended net system contained by a lanyard to sample a 3-meter deep well. Our trap modifications resulted in the live capture of adult and immature federally threatened Salado Salamanders (Eurycea chisholmensis) from the well in addition to aquatic invertebrates. This represents a novel trapping technique within a habitat system for which stygofauna sampling options are limited.
Active trap, Amphibian sampling, Karst Biology, Leaf litter trap, Salado Salamander, Stygofauna, Threatened Species
Knowledge of stygofauna and their ecology is inevitably less available than that of epigean fauna because the subterranean habitats stygofauna occupy are less accessible for sampling (
Subterranean sampling and trapping techniques have been developed to survey areas inaccessible to humans. Commonly employed methods for sampling stygofauna have been restricted to the hyporheic zone using water well or bore sampling, as well as the deployment of traps (
Despite extensive research on invertebrate sampling, methods for effectively sampling subterranean vertebrates remain less established. Although the use of bottle and funnel traps to sample for stream-dwelling (i.e., epigean) salamanders is also well documented (e.g.,
A popular technique for sampling surface (i.e., epigean) stream-dwelling salamanders is the use of leaf litter bags (
In surface waters, researchers check leaf litter bags by quickly sliding a tray or sieve under the bag to catch any target fauna that may fall through the mesh netting (
The target of this sampling methodology was Salado Salamanders (Eurycea chisholmensis), a fully aquatic groundwater obligate salamander. Salado Salamanders are the northernmost species within a radiation of central Texas Eurycea salamanders and are endemic to groundwater habitats north of the San Gabriel River and south of Salado Creek in Williamson and Bell counties, Texas. (
Cobbs Spring is ephemeral and discharges from the northern segment of the Edwards Aquifer in the Berry Creek watershed and is located on private property within Williamson County, Texas, USA. The soil and associated geology near the spring consists of silty and clayey slope alluvium underlain by Edwards limestone. Pecan (Carya illinoinensis) is the dominant overstory vegetation surrounding the spring. Within the spring run, the Edwards limestone is weathered entirely exposing the topmost Comanche bedrock.
Early settlers of this property installed an approximately 3 m deep hand-dug well (Fig.
We modify a commonly used and documented trapping technique for stream-dwelling salamanders (
Our goal when designing this trap method was to create a leaf litter bag that could be lowered into a well within a mesh bag (Figs
Lowering the Leaf Litter Trap into the Well. The image shows the trap being lowered into the well using the lanyard. The leaf litter bag, contained within the pool net, is carefully guided down to the bottom of the well, positioning it to lay flat and become accessible to salamanders. This setup ensures a smooth descent and accurate placement of the trap in the well.
Leaf litter bag with no lanyard tension. Illustrating how the leaf litter bag is fully accessible to salamanders when the pool net lies flat against the bottom of the well, with no tension on the lanyard. This design ensures that the leaf litter bag provides unobstructed access to the trap contents, allowing salamanders to enter and leave freely.
Leaf litter bag with lanyard tension. Demonstrating the trap in its closed position with tension applied to the lanyard, causing the pool net to enclose the leaf litter bag. This configuration securely captures the salamanders and prevents their escape, ensuring all animals within are retained during extraction.
The trap was checked four hours after first deployment (Fig.
First captured Eurycea chisholmensis with this trap. The first two federally listed E. chisholmensis salamanders captured using the modified leaf litter trap. One is an adult, and the other is a juvenile, showcasing the trap’s effectiveness in capturing different life stages. Photos of these salamanders were taken to be able to identify them as recaptured in successive surveys using the Wild ID software.
A total of 18 salamanders were captured, representing 12 unique individuals (determined through capture mark recapture methods) (Table
Salado Salamander (Eurycea chisholmensis) measurement and gravidity data.
Date | Salamander Unique ID | Total Length (mm) | STL (mm) | Gravid |
---|---|---|---|---|
31 Oct 2019 | C0432 | 24.1 | 14.6 | No |
C0433 | 47.1 | 25.9 | No | |
20 Nov 2019 | C0434 | 32.4 | 18.3 | No |
C0435 | 33.7 | 18.6 | No | |
C0436 | 43.2 | 23.0 | No | |
19 Dec 2019 | C0432 | 24.9 | 15.8 | No |
C0454 | 43.6 | 25.7 | No | |
C0435 | 33.6 | 19.3 | No | |
27 Jan 2020 | C0435 | 34.7 | 19.0 | No |
C0470 | 40.6 | 22.5 | No | |
C0471 | 30.3 | 17.7 | No | |
24 Feb 2020 | C0493 | 32.6 | 19.2 | No |
C0494 | 31.5 | 20.0 | No | |
C0495 | 34.0 | 21.0 | No | |
C0470 | 41.2 | 23.9 | No | |
C0471 | 31.6 | 20.4 | No | |
C0496 | 42.2 | 24.5 | No | |
C0432 | 28.4 | 17.7 | No |
Salado Salamander (Eurycea chisholmensis) capture results using the modified leaf litter trap.
Date | Deployment Time | Total Adult Captures | Total Juvenile Captures | Recaptured Individuals |
---|---|---|---|---|
31 Oct 2019 | 4 hours | 1 | 1 | – |
20 Nov 2019 | 20 days | 3 | 0 | 0 |
19 Dec 2019 | 29 days | 2 | 1 | 2 |
27 Jan 2020 | 39 days | 3 | 0 | 1 |
24 Feb 2020 | 28 days | 7 | 0 | 3 |
Stygofauna are understudied, and many species within this group are of conservation concern due to their cryptic nature (
Although this water well is shallow and open to the surface, we expect the methods we describe above to be applicable to a variety of sampling requirements and unique situations. The successful capture of salamanders within this well, given its proximity to the known occupied spring, demonstrates the use of subterranean habitat by this species within the karst subterranean habitat that underlies the uplands.
The recapture of 6 unique individual salamanders over five sampling events without mortalities demonstrates that salamanders can enter and leave the trap safely. This trap was designed specifically for this well, but it could potentially be used as a sampling technique for other wells, caves, and hard-to-reach places in occupied springs. This methodology may also have utility to inventory invertebrates that utilize leaf litter, and in federally mandated occurrence surveys for this group of salamanders (USFWS 2021). With some modifications, we expect that this trap can be deployed in various deep-water settings, caves, solution cavities, and wells of different sizes and depths. Additionally, the leaf litter bag could be replaced by other artificial structures meant to attract fauna, such as mop heads, which are commonly used to sample both groundwater salamanders and invertebrates (e.g.,
This work was supported by the Williamson County Conservation Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.