Small Scale-High Resolution Terrestrial Activity of Trachemys scripta elegans, Harvest Intensity, and Immediate Movement Responses Following Harvest Events
Overland movement is an important aspect of freshwater turtle ecology. Turtles make overland excursions searching for mates, to find new aquatic habitats, in response to drought, or during nesting. Here, we tested how environmental factors may influence the excursion events of adult Red-eared Sliders (Trachemys scripta elegans). We found that 85% of turtles made overland movements at least once, which is higher than previously reported, and some turtles made multiple movements (2–6) during a single season. Rain and drought events were significant predictors of overland movements. While sex did not appear to be a significant factor, there was an indication that movement may depend on seasonal temperatures. In addition, we showed that turtles immigrated to depopulated ponds in a short period of time after a simulated harvest event. However, after a second harvest simulation, our experimental pond was not repopulated to its original abundance. Our results call for caution when implementing spatially controlled harvest regimes. Ponds depleted by harvesting might not be repopulated by immigrating turtles if source population sizes also decrease due to the regular dispersal to sink populations and subsequently slows overall reproduction rates.
Aerial view of the study system showing the ponds and location(s) of the movement monitoring system, turtle gate, consisting of the game camera and the PIT tag reader. The first turtle gate was installed between the Enclosure Pond and the Lake in July 2011. The main focus of the experiment was the Enclosure Pond for which the exact number of resident turtles was known at any given time. The second turtle gate was installed between the House Pond and the Lake in 2013 and was only used for comparison of overall activity between the two gates.
Daily activity peaks of Red-eared Sliders (Trachemys scripta elegans) per season. All turtles showed diurnal activity. Turtles were active throughout the day during spring, but only early in the morning during summer. In winter months, they tend to be more active during midday.
The number of Red-eared Sliders (Trachemys scripta elegans) in the Enclosure Pond at the end of each month from July 2011 to October 2013. The population size was calculated based on the chip reader data and the game camera data recording the movement. Two harvest simulations took place, in May 2012 and June 2013, and the graph also presents the number of turtles immediately after harvest events (red circles).
Contributor Notes
Associate Editor: M. J. Lannoo.