Authored by Houston Chandler
With the 2016–2017 Eastern Indigo Snake (Drymarchon couperi) sampling season nearing its end, we have started preparing for the upcoming Spotted Turtle (Clemmys guttata) trapping season. This will be our fourth consecutive year of monitoring and research on Georgia populations of Spotted Turtles. It is the first time Georgia Spotted Turtle populations have been studied extensively over many years, and we have already learned some interesting things about these wonderful turtles.
Spotted Turtles congregate in mating aggregations during the spring, making them easier to catch in large numbers than at other times of the year. To capture turtles, we deploy specially-designed turtle traps in locations where Spotted Turtles may frequent, generally in shallow water near logs or other debris. It is not uncommon to catch several turtles in a single trap, and previous research has indicated that turtles are actively attracted to traps that already have an individual inside. Upon capture, each turtle is sexed, measured using standard turtle measuring techniques and weighed. Before being released near the point of capture, each individual also receives a unique number by filing small notches into the marginal scutes.
Over the last three years, we have captured and marked 82 Spotted Turtles at two long-term monitoring sites. Many of these individuals have been captured in multiple years and approximately 70 percent of the turtles have been recaptured at least once. In each consecutive trapping season, the number of new individuals captured steadily decreases as a larger percentage of the population is captured and marked. However, it is unlikely that we will ever catch all of the adult turtles at each site, and new turtles are continually joining the population. For example, last year we captured several juvenile turtles and x-rayed adult females with eggs, indicating that reproduction is occurring in both populations. During the upcoming season we will likely catch mostly turtles that have been captured in previous years, including some old favorites like “Igor” or “Sofia,” but hopefully there will also be a handful of turtles new to the study.
In addition to the normal Spotted Turtle monitoring work, we also spent a large portion of 2016 radio-tracking turtles from both long-term monitoring sites. It is tough work following the same turtles around for nine months, and there are many distractions (some may wish to read this as hazards) to avoid while wandering around southern Georgia swamps in the middle of the summer. These most notably included chest-deep muck, Golden Silk Orb Weavers (Nephila clavipes) and other large spiders, hornet nests, and the occasional Cottonmouth (Agkistrodon piscivorus) or Copperhead (A. contortrix). This all made for an interesting summer and fall.
It did not take long for us to learn which turtles were prone to long movements or likely to be in difficult locations and which turtles rarely moved. When spending so much time in the same places and finding the same animals on so many occasions, it often leads to interesting observations that would have gone unnoticed otherwise. We followed turtles to locations where we never would have guessed a Spotted Turtle would end up on its own, including out of the wetlands and into surrounding forests. We observed turtles feeding on Mosquitofish (Gambusia) and basking in the late morning sun. One of the more interesting observations included multiple turtles engaged in courtship behavior during September and October, which is outside of the normal breeding season. We observed male turtles chasing females on multiple occasions and even saw one male riding around on top of a female for an extended period of time. These observations are supported by similar observations in Florida, suggesting that some individuals in southern populations of Spotted Turtles may actually mate in the spring and fall.
At the end of December 2016, we concluded the radio telemetry study by removing the radio transmitters and temperature loggers from the 29 turtles that were originally instrumented. Over the nine-month tracking period, we relocated turtles a total of 1,246 times. We recorded various information about the turtle’s behavior and habitats each time a turtle was located, and the temperature loggers continuously recorded shell temperature every 90 minutes. All this adds up to a lot of data that we can use to better understand Spotted Turtles in Georgia.
At the most basic level, radio telemetry data allows us to examine the movement and space use of each individual turtle and of the population as a whole. This includes calculating estimates of home range size or the area that a turtle has used during the tracking period. Overall, the Spotted Turtles that we followed last year had small home range sizes that rarely exceeded 15 hectares in total area, although there were a couple notable exceptions. These were the turtles that tended to move long distances into new locations, which made them often the most difficult turtles to locate while tracking. “Chunky” was particularly difficult at times and had the largest estimated home range of any turtle included in the study.
The home range estimates and other telemetry data from last year will be used to help us identify sites that may be suitable for Spotted Turtle populations. There are few documented populations of Spotted Turtles in Georgia, and we plan to conduct more inventory work across the state to identify additional populations. In conjunction with this effort, we have created a habitat model for Spotted Turtles in Georgia using all known occurrence records. Through a combination of these efforts, we will continue to learn more about Spotted Turtle populations in Georgia and to identify the best ways to effectively manage populations in an ever-changing world.