Six years of Spotted Turtle Monitoring

We recently wrapped up our sixth consecutive year surveying for Spotted Turtles (Clemmys guttata) in Georgia. This year was exceptionally challenging with dry conditions hampering survey efforts in late April and May. Many wetlands favored by Spotted Turtles were completely dry well before the end of the sampling season. A stark contrast to last season when wetlands were flooded throughout the second half of the survey season by repeated heavy rains. This type of yearly variation in environmental conditions is one of the reasons why long-term surveying is necessary to really understand wild animal populations. With this in mind, let’s take a look at some of the things that we have observed over the last six years.

The Orianne Society’s work with Spotted Turtles began in 2014 when Dirk Stevenson began catching and marking turtles at one of the only known populations on public property in Georgia. Since that first year, we have marked 92 individuals in this population through a combination of trapping and visual encounter surveys. These 92 individuals have accounted for 507 total capture events! Turtles were most commonly encountered in traps (ca. 63% of all capture events), but there was substantial variation, both in capture method and frequency of capture. For example, ‘Ditch Boy’ has been captured 22 times in traps but just 4 times by hand, while ‘Peggy’ has been captured in traps just 3 times and by hand a total of 10 times. Over six seasons of trapping, some turtles seem omnipresent, while others seem to disappear into the murky water, never to be seen again. ‘Gulliver’ has been captured a whopping 35 times in six years (9 more than the next highest total). Conversely, two individuals were captured in 2014 and have not been seen since. Overall, we have had incredible success catching turtles in this population and have averaged approximately 40 individuals per season.

The second population of Spotted Turtles that we are currently monitoring was first visited in 2015. This populations is the polar opposite of the first population in many ways. Over five years of monitoring, we have marked just 38 turtles, accounting for 153 capture events. Captures of new adult turtles decreased to just 1–3 per year after the second year of surveys, although three new individuals were captured on different parts of the same property in 2018 and 2019. These captures indicate that a larger meta-population likely exists on this property. Trap captures again produced the majority of capture events, although at a slightly lower percentage (56%). At this site, ten individuals have only been captured by hand, and environmental differences, particularly shallow, isolated pools, appear to make trapping less successful overall.

Over the last six years, we have spent thousands of hours at these two sites while surveying for turtles, radio tracking turtles, and searching for turtle nests. All of this time in the field has generated great data and led to many interesting observations that shed light on what it means to be a Spotted Turtle population in Georgia. Here are a few of the interesting things that we have observed:

• Both turtle populations inhabit a complex of disjunct floodplain pools. Water depths rarely exceed 300 mm, and turtles are often observed in water that barely covers their shell. Movements between pools and different areas of the wetland are common, especially during times of the year when courtship behavior occurs.

• Turtles at both sites have been observed active in the water in 11 of 12 months. January is the only exception, and it is highly likely that turtles can be active on warm January days. We have never visited either site in January.

• We have captured hatchling, juvenile, sub-adult, and adult turtles in both populations, although hatchlings and small juveniles are captured at significantly lower rates (ca. 12 individuals captured with a carapace length less than 60 mm). This is likely due to sampling bias that limits our ability to locate these small turtles. They are most commonly encountered on the margins of the main swamps in water that is just a couple of inches deep.

• Many turtles in both populations spend a significant amount of time each year on dry land. Site 2 is especially prone to drying in late spring and summer without regular precipitation events. Turtles in this population likely spend several months each year with little to no access to water.

• Courtship behavior commonly occurs in both spring and fall. Males actively chase females in both seasons and in some cases cover long distances to locate female turtles.

• Turtles have been observed feeding on a variety of prey items, including amphibian eggs, fish, tadpoles, and aquatic invertebrates.

I look forward to Spotted Turtle season each year, and these diminutive turtles are a pleasure to work with, despite the fact that surveying for them is often frustratingly difficult. It has taken several years to learn both of these sites and identify locations where turtles are most likely to be captured. Despite this familiarity with survey sites, results can still be mixed. From 2016–2019, we conducted 783 trap nights at Site 1 (one trap in the water for one night), and we had a total of 252 Spotted Turtle capture events. This equals about 0.3 Spotted Turtle captures per trap night, which is actually a somewhat favorable capture rate. At Site 2, we conducted a total of 815 trap nights over the same time period. However, this higher effort resulted in just 59 total Spotted Turtle captures; a capture rate of just 0.07 turtles per trap night! The smaller population at this site certainly hampers our trapping efforts, but Spotted Turtles are often just hard to catch.

Over six years, we have learned an incredible amount about the ecology of Spotted Turtle populations in Georgia. This type of yearly long-term monitoring is a crucial component for an effective conservation program, and the data collected will directly inform conservation planning and upcoming listing decisions.