Diamondback Terrapin Population Distribution and Nesting Areas in Coastal Georgia

Presenter Information

Grace Clements
Joseph Butler PhD

Faculty Sponsor

Dr. Joseph Butler, PhD, Dr. James D. Lambert, PhD

Faculty Sponsor College

College of Arts and Sciences

Faculty Sponsor Department

Biology

Location

SOARS Virtual Conference

Presentation Website

https://unfsoars.domains.unf.edu/diamondback-terrapin-population-distribution-and-nesting-areas-in-coastal-georgia/

Keywords

SOARS (Conference) (2020 : University of North Florida) -- Posters; University of North Florida. Office of Undergraduate Research; University of North Florida. Graduate School; College students – Research -- Florida – Jacksonville -- Posters; University of North Florida – Undergraduates -- Research -- Posters; University of North Florida. Department of Biology -- Research -- Posters; Biology; Physics; and Chemistry -- Research – Posters

Abstract

The terrapin population range is small and the research is scarce. Surveil of the entire Georgia coast is the overarching goal of the research and the past four years have already resulted in 60% percent of the state completed and 1500 records accomplished. Coverage of the coastline will be continued in 2019 in the southernmost county, Cambden, and in 2020 completing the research in the northernmost county, Chathman. Diamondback terrapins are the only turtle to prefer brackish water habitats and are the first to be affected by sea level rising. Crab pots are a main factor in terrapin mortality. When they are collected, it is too late for the terrapin because they have already drowned (Butler and Heinrich 2007). Shoreline hardening makes it impossible for terrapins to journey onto land because they cannot cross the large rocks or cement walls. The work will be carried out utilizing a 16 foot Carolina skiff to navigate into rivers and creeks searching for evidence of terrapin presence. Capturing a live terrapin is not necessary. Evidence is found in the form of surfacing heads, intact and depredated nests, terrapin remains, live terrapins, and crawls (trails). One of the primary goals of the main conservation body of turtles; The Diamondback Terrapin Working Group (www.dtwg.org), is to identify the remaining locations of nesting and terrapin population so accurate management and categorization of terrapin information is carried out. We will create ARCGIS maps that illustrate geolocations reflecting our findings, and aid future researchers.

Comments

Hi! My name is Grace Clements and it will be my pleasure to direct you through this poster as you read it or as you listen to me while I give you the breakdown. Of course, with the lack of in-person gestures directed to the poster it will be a little different but I will try my best to navigate you verbally.

The goal of this research is to survey the Georgia coastline for evidence of diamondback terrapins. Diamondback terrapins are a type of turtle that lives specifically in brackish water. This means that it is water of average salinity levels usually around 35 ppt. Because of their habitat, they are an indicator species of sea level rise. Dr. Butler has been working on this research for six years now and I have been lucky enough to be a part of it since my freshman year in 2017! As you may read in the introduction, little research has been conducted on this species mostly due to the environment they live in because it is hard to access. The UNF terrapin team will be the first to complete a survey of the whole Georgia coastline for presence of these amazing animals and we hypothesize that with adequate time and effort, baseline population data acquisition is possible.

Now moving on to the methods. We carry out our survey on a small skiff and by foot looking for forms of terrapin evidence with the naked eye. If you direct your attention to the table, you can see the forms of terrapin evidence we look for. The top three are depredated nests, heads, and terrapin remains. If you look at the top left image, this is an example of a depredated or (what we informally call) a raided nest. These are found on foot and the first indication that we look for is egg shells. The main predator of terrapins are raccoons. They dig up the eggs and consume them all leaving the eggshells behind (other predators can include ghost crabs and birds as well). Head data is collected on the water while in the boat. The team carefully analyzes the surface of the water for terrapin head emergence. Terrapin remains are commonly found in the form of bones, shells, and carcasses. Sometimes entire dead female terrapins are found intact with a hole in their side where a raccoon tore the eggs out. An example of a crawl can be seen in the image at the top right-hand corner. These are basically the tracks that a female terrapin leaves behind when coming onto land in search of a place to lay her eggs, or returning to the water. As you can imagine these are rarer because the sand does not remain unchanged for very long. If a live terrapin is found (top right image) we take this opportunity to record morphological data. As you may have noticed, I am mostly speaking about female terrapins. This is because male terrapins stay in the water most of their lives because they don’t need to lay eggs!

Please shift your attention to the two map figures. In Figure 1., the blue triangles represent where our boat has traveled. As you can see I-95 is usually our westward limit because salinity decreases westward and terrapin numbers decline. In Figure 2, the red triangles represent locations for where we collected one of the seven forms of evidence listed in Table 1. As we come across evidence in the field, we record it on an Ipad through the GIS collector app which we can then revisit and make maps from. If all goes as planned this summer of 2020, we will be able to survey the final section (indicated by a pink rectangle in Figure 1.) of the coastline and complete the experiment.

Id now like to discuss some of our findings so far. If you could look in Figure 2 at the Altamaha River (in the middle) you may see that there are little to no forms of evidence recorded there. This may be due to the length of the river and the amount of freshwater coming in from the west. This signifies again, the preference of terrapins for a very specific salinity level because if you look not very much further down in Brunswick, our records of evidence spiked. Another interesting trend would be in the Satilla River (bottom of map above Cambden county). There are less forms of evidence in this area possibly due to the width of the river’s mouth. The speed of the water in this wider river is comparably faster than that of smaller creeks. Therefore, the terrapins do not want to spend that energy fighting the current!

As stated before, the experimental goal is to survey the Georgia coastline for terrapin evidence. The data is not an exact representation of terrapin population numbers, but without baseline population data there is no way to defend this species or see how their numbers are changing. With this data, we can advocate more strongly for prevention of construction, shoreline hardening, and crab traps in this area. We can also continue to revisit these areas and see how the population has changed since the initial survey in conjunction with sea level fluctuations.

Thank you so much for listening/ reading my presentation and I hope you are as excited I am for the completion of our research and furthering of terrapin knowledge!