Sapelo Research Application Form
Research Application ID: GCE-148-2026 (submitted: 01/26/2026, status: approved)
Provide a brief title for web display
Examining the effects of predator risk and environmental conditions on burrow distribution and behavior of mud fiddler crabs
Investigator Information
On Island Sponsor: GCE SINERR UGAMI GADNR
| Principal Investigator: | Shelby Ziegler | ||
| Home Institution: | Villanova University | ||
| Award Information: | NA, Ziegler start up funds | ||
| Mailing Address: | Mendel Hall Rm 190A | Phone Number: | |
| Biology | E-mail Address: | shelby.ziegler@villanova.edu | |
| Villanova, Pennsylvania 19085 | |||
| Co-investigators: | |||
Briefly describe the project goals and methodology
The main objective is to quantify the relative importance of abiotic (sediment characteristics) and biotic (predator risk and vegetation structure) factors shaping the spatial distribution and density of Minuca pugnax burrows.
Four subsites will be selected to capture within-marsh variation in elevation, vegetation structure and flooding regime. Within each subsite, three transects will be established perpendicular to the nearest tidal creek and extended 50 m into the marsh interior. Along each transect, sampling will occur at six fixed distances (0, 10, 20, 30, 40, and 50 m), spanning the low-marsh (0-20 m) and mid-marsh (20-50 m) zones. All surveys will be conducted during daytime low tide when the marsh platform is exposed, and burrow openings are visible.
At each transect distance, burrow density will be quantified within a 25 x 25 cm quadrat (0.0625 m2) placed flush with the sediment surface. All burrow openings meeting the field identification criteria for M. pugnax will be counted (burrows ≤ 1.3 cm in diameter).
Abiotic variables will be measured at each quadrat to characterize constraints on burrow construction and persistence. Elevation will be measured at each transect distance using a Emlid RTK GNSS. Sediment compaction will be measured once per quadrat using a handheld field penetrometer at a standardized insertion depth. Sediment moisture will be gravimetrically from a 0-10 cm core (5 cm internal diameter) collected within the quadrat, sealed immediately and processed in the laboratory as percent water content following drying at 60°C for 48 h ([wet - dry)/dry] x 100). Porewater salinity (psu) and pH will be measured from 0-10 cm porewater extracted using a sipper and recorded with a handheld salinity refractometer and pH indicator strips, respectively. Sediment temperature (°C) will be recorded at the surface (0-1 cm) and at the subsurface (10 cm) using a digital thermometer probe. Inundation regime will be quantified using existing site-specific tide/water level data supplemented by in situ water loggers deployed at representative elevations during the sampling period , providing an integrated inundation metric for analysis. Additionally, vegetation structure will be quantified within each quadrat as live S. alterniflora stem density (stems per 0.0625 m2) and maximum stem height (cm). The presence of bare sediment or algal mats will be recorded using categorical cover classes.
Predation risk will be quantified using a standardized tethering assay with paired exposed and protected (caged control) treatments deployed adjacent to each sampling distance alongside the same survey quadrat (Figure 3). Adult male M. pugnax (13-20 mm carapace width) will be collected land tethered with monofilament line secured to the sediment to a lawn staple. During deployment lawn stable with tethered crab will be secured to the sediment. Paired treatments will be deployed simultaneously at each transect distance: (1) exposed tether and (2) caged control (mesh enclosure) to quantify non-predation losses. Deployments will be standardized in duration and tidal timing during low tide (typically ~3 hours) across sites.
Where will the project be located?
Dean Creek Marsh, Transects will be placed within these points (creates a polygon): 31°23'21"N 81°16'42"W, 31°23'17"N 81°16'32"W, 31°23'22"N 81°16'30"W, 31°23'23"N 81°16'40"W
How will you provide GPS coordinates for study sites?
GPS coordinates are listed in the project location field
What are the expected start and end dates of the project?
Start Date: 05/24/2026 End Date: 06/03/2026
How many people will access the site and at what frequency?
3 people for 10 days total
Keywords that describe your project
What equipment will be deployed in the field?
PVC poles (4 total, 10ft, removed each day), small vexar cages (18 total, ~30 cm tall, 10cm diameter, removed daily after each experiment)
Will plants or animals be collected as part of this study?
We will be collecting and tethering Minuca pugnax. For each, predation experiment we will use 36 fiddler crabs for a total of 144 across four days. We will reuse any live animals on the subsequent days.
What are the likely impacts of the project on the site?
We believe there will be minimal impacts to the site. We will be walking out to the creek bank which may result in trampling of vegetation. We will be placing PVC and small cages (<1ft tall) over the course of 4 days which will be removed daily. We will also be taking small sediment cores (72 total) for post processing in the lab: 10 cm depth core with 5 cm internal diameter. We will be collecting and tethering Minuca pugnax. For each, predation experiment we will use 36 fiddler crabs for a total of 144 across four days. We will reuse any live animals on the subsequent days.
Will the project design include boardwalks? If not, explain why not.
How long will impacts persist after the research is concluded?
We expect minimal impact to the site and expect it to return its initial state within 1-2 weeks of sampling
