Searching for Terrapins in the Florida Panhandle

by Rick O'Connor | Dec 22, 2021

2021 Panhandle Terrapin Project Survey Report

Rick O’Connor, Florida Sea Grant, University of Florida / IFAS Extension, Escambia County

SITUATION

The diamondback terrapin (Malaclemys terrapin) is the only resident brackish water turtle in the United States.  Ranging from Cape Cod Massachusetts to Brownsville Texas, this turtle is most often found in the salt marsh and mangrove habitats within this range.

The light colored skin and dark markings are pretty unique to the terrapin.
Photo: Molly O’Connor

Terrapins are medium sized members of the Emydidae family, which includes the cooters, sliders, and box turtles. The carapace length of the larger females is about 10 inches, and she will weigh on average about 20 ounces.  Males are smaller, 5-6 inches carapace and about 10 ounces.  They are beautifully marked turtles having lighter skin with darker spots or bars.  The carapace can have beautiful markings of spots and swirls, many times a brilliant orange in color.  Because of this they are popular in the pet trade and illegal pouching is a problem across their range.

There are seven subspecies within this range.

• The northern terrapin ( t. terrapin) can be found from Massachusetts to the Chesapeake Bay area.
• The Carolina terrapin ( t. centrata) is found from the Chesapeake Bay area to the Daytona Beach area of Florida.
• The Florida east coast terrapin ( t. tequesta) is found from the Daytona Beach area to Miami-Dade County.
• The mangrove terrapin ( t. rhizophorarum) is found in the Florida Keys and along the Gulf coast to the Ten Thousand Islands area.
• The ornate terrapin ( t. macrospilota) can be found from the Ten Thousand Island area to Choctawhatchee Bay in the Florida panhandle.
• The Mississippi terrapin ( t. pileata) is found from Choctawhatchee Bay to the Louisiana/Texas state line.
• The Texas terrapin ( t. littoralis) is found along the coast of Texas.

The animal is quite well known in the Chesapeake Bay area where it was harvested in the 19^th century as a food source.  The popularity of “turtle soup” increased when President Lincoln included it as a local course for state dinners at the White House.  The popularity increased the harvest to a point where terrapin farms began to supply the demand, many of these farms were in the south.  Eventually the price became too high, and the popularity of the dish waned.  At that point research into the animal began in earnest to assess how the commercial harvest had impacted the population.  Much of this work was conducted in the early part of the 20^th century.  By the mid-20^th century, a wired crab pot was developed for the harvest of blue crab, a popular fishery in the Chesapeake.  Terrapins have a habitat of entering these crab pots and drowning.  So, a new threat had emerged.  About the same time the automobile was becoming more popular, bridges were being built to connect to barrier islands, and other locations, humans had not visited much before.  This activity increased the number of nest predators for terrapins, raccoons being one of the larger problems.

Terrapins in a derelict crab trap (photo: Molly O’Connor)

All of these issues led to more research on terrapin biology and ecology.  However, there was one region within their range that very little was known – the Florida panhandle.  There were no scientific studies conducted in this part of their range and even their existence there was questioned.

REPSONSE

In response to the question of existence in the Florida panhandle, the Florida Turtle Conservation Trust and the Florida Diamondback Terrapin Working Group, reached out to the Institute of Coastal and Marine Studies (a high school marine science program in Escambia County, Florida).  The objective was to have them conduct surveys in suitable terrapin habitat indicating presence/absence of terrapins between Escambia and Franklin Counties.  Those surveys began in 2005 and by 2010 had been conducted in all six counties with at least one verified record in each of the six counties (Escambia, Santa Rosa, Okaloosa, Walton, Bay, and Gulf).  Terrapins did exist there.

Beginning in 2008 the team began to assess population status.  Funding for mark/recapture was not available but a method of assessing relative abundance was being used in Mississippi and was chosen for the Florida panhandle.  The method had made several assumptions –

• Each mature female nests every nesting season
• Each nesting female will lay more than one clutch each season but would not lay more than one within a 16-day period.
• The team had identified all terrapin nesting beaches in the region.

Based on this method, surveys were broken into 16-day intervals beginning April 1 and ending on July 1 (peak nesting period).  Each track, or depredated nest, was counted and all sign of the track or nest removed so that it would not be recounted within that 16-day period.  Each track would then represent a different female and over time the number of nesting females could be determined.  Going on the argument that the sex ratio was 1:1 a relative abundance of adult terrapins could be determined.  A study conducted in the Big Bend area of Florida by Suarez (Suarez, 2015) suggested the sex ratio was 1:3 in favor of males.  A more recent study from the eastern panhandle conducted by Catizone (unpublished) suggests a 1:5 ratio in favor of males.  Based on this we could develop a range of relative abundance from 1:1 to 1:5.

Note the track on this beach.
Photo: Rick O’Connor

Egg shells indicate a depredated nest.
Photo: Rick O’Connor

Another metric used to measure relative abundance was a 30-minute head count.  The team would sit in kayaks within the ponds where adults resided and count the number of heads in that time period.  Again, this does not indicate a population but a relative abundance within that location.

Finally, in 2008 the team began to deploy modified crab traps to capture terrapins for a potential mark/recapture study, marking using a scute notching method.  The traps were modified so that a captured terrapin would be able to surface and breath.  These traps were set in potential adult residing locations for a five-day period beginning on a Monday and ending on a Friday.

A terrapin swimming near but not entering a modified crab trap.
Photo: Molly O’Connor

The focus of the relative abundance and trapping portions of the project were Escambia and Santa Rosa Counties due to the fact the team resided there.

In 2012, the author left the marine academy and joined Florida Sea Grant.  This project was not a high priority in the job description and effort on this waned until no surveys were conducted in 2014.  However, in 2015 the author established a citizen science program to continue these surveys and they have done so since.  The focus of those surveys has been frequency of occurrence (FOO – the number of surveys where either terrapins, or terrapin sign have occurred) and continuing the relative abundance data collection.

Citizen scientists have been crucial for the success of this project.
Photo: Rick O’Connor

In 2018 the U.S. Geological Survey joined the team. One member of USGS began coordinating citizen science work in the eastern panhandle (Bay, Gulf, and Franklin Counties as well as conducting research in the Gulf County area), and the author began coordinating citizen science work in the western panhandle (Escambia, Santa Rosa, Okaloosa, and Walton Counties). With USGS help some tagging has begun with both PIT and satellite tags.

RESULTS

The 2021 results are from the western panhandle portion of the project.

In the western panhandle during 2021, 263 surveys were conducted by 41 trained volunteers who logged 1832 hours. These surveys occurred in Escambia, Santa Rosa, and Okaloosa Counties. Surveys were conducted at known nesting areas with some occurring at potential new nesting sites. The number of surveys where either terrapins, or terrapin sign, were encountered was 52. This is a frequency of occurrence (FOO) of 20% of the surveys an encounter occurred. The breakdown by county is below.

2021 Data from the Western Panhandle 

Three of the eight sites surveyed in Escambia County were known nesting beaches, but evidence of nesting was only found at one. The other five locations were potential nesting sites, but no evidence of nesting was found. Based on these surveys, nesting activity declined in 2021.

Both sites surveyed in Santa Rosa County were known nesting beaches and nesting was detected at both. One site has long term data that, based on this year’s surveys, suggest a decline in relative abundance.

One of the five sites in Okaloosa was a known nesting site. However, evidence of nesting at a additional site was found. An encounter of some kind was logged at four of the five sites surveyed. All of these are relatively new survey sites to the project and relative abundance data is minimal. However, based on these data, the relative abundance is quite high.

Data from 2007 – 2021 for all sites

Since the beginning of the project 859 surveys have been conducted in the four counties of the western panhandle and terrapins have been encountered 25% of the time. Of the 50 sites surveyed, 8 (16%) of those have found nesting activity.

Objective 1 has been completed. There are terrapins in the Florida panhandle.

Objective 2 – the relative abundance – is still not completely understood. There was a significant decrease in encounters when the citizen science project began in 2015.
The citizen science effort the FOO was much higher and increased annually. The citizen science effort began in 2015 and the FOO was much lower but increased annually as well. It is believed that the cause of this decline is ability for volunteers to find terrapins, terrapin heads, or evidence of nesting. It is believed the volunteers are getting better and that the data will eventually provide better information on terrapin abundance.

DISCUSSION

Objective 1 has been answered. There are terrapins in the Florida panhandle.

Objective 2 is still not understood. It is believed the higher FOO between 2007 and 2011 was probably due to the ability of the volunteers to detect terrapin or terrapin sign. So, it is not known at this time whether the relative abundance of these animals have declined in the western panhandle or not. As the volunteers get better, we will see over time how the numbers change.

The effort of mark/recapture using modified crab traps has not been very effective. Traps have been deployed with much effort at four sites with very little success. That portion of the project has been suspended while searching for a better method of capture.

At two of the long-term monitoring sites, the relative abundance data suggests a decline in terrapins at those locations. However, as mentioned, confidence in the relative abundance data needs to increase before any strong conclusions can be drawn. These data do suggest small populations at all locations, between 20-50 animals. The citizen science effort will continue, and we hope a more robust population study will follow.

ACKNOWLEDGEMENTS

The author would like to thank the students from the Institute of Coastal and Marine Studies at B.T. Washington High School for assistance developing and conducting the early portion of this project.

Tom Mann from the Mississippi Department of Wildlife for the protocol on relative abundance based on nesting activity.

George Heinrich (Florida Turtle Conservation Trust, Florida Diamondback Terrapin Working Group)
Dr. Joe Butler (University of North Florida, Florida Diamondback Terrapin Working Group)
Dr. Andy Coleman (Birmingham Audubon Society, Gulf Coast Diamondback Terrapin Working Group)
Dr. Thane Wibbels (University of Alabama Birmingham, Gulf Coast Diamondback Terrapin Working Group)
Dr. Ken Marion (University of Alabama Birmingham, Gulf Coast Diamondback Terrapin Working Group) for their assistance, guidance and advice on this project.

Dan Catizone (U.S. Geological Survey, University of Florida)
Dr. Margaret Lamont (U.S. Geological Survey)
for their assistance, guidance, advice, and supply support.

Bob Pitts (Gulf Islands National Seashore)
Bob Blais (Navarre Beach Sea Turtle Conservation Center)
Jeanna Kilpatrick (Choctawhatchee Basin Alliance)
for taking the lead as county volunteer coordinators as well as surveyors.

And the 40 plus volunteers who have logged thousands of hours surveying sites in the western panhandle. We could not have done this without you.

Submitted:
December 22, 2021.