Fine-scale Movement Ecology of Wood Turtles (Glyptemys insculpta) Based on GPS Tag Data and Movement Modeling



Drescher-Lehman, Jonathan

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Little is known about long-distance dispersal movements in freshwater turtles, despite the probable importance of such movements for gene flow between populations. There is a pressing need to better understand these movements, especially within the context of an increasingly fragmented landscape. This study aimed to look at these and other longdistance movements by tracking wood turtles (Glyptemys insculpta) using miniaturized GPS units attached to their shells. The data were also used to estimate home range sizes and movement speeds, as well as to analyze the shift in these metrics throughout an active season. In total, 61 wood turtles (38 females, 23 males) were tracked for one to three years each, with hourly or sub-hourly locational fixes recorded for the duration of the active seasons. Two datasets, one from Minnesota (n=25) and one from Virginia (n=36), were combined for a total of over 140,000 GPS locations. Our results show that traditional measures of home range significantly underestimate actual home range sizes for wood turtles. In Virginia, home range area and movement speed both increased significantly and peaked for females during the nesting season, while male movement was more consistent throughout the year. Movement speed for females peaked during the nesting season. These trends were not observed in the Minnesota population. We captured numerous long-distance nesting movements, two long-distance relocation movements following flood displacement events, and two long-range dispersal events by younger male turtles. Our data demonstrate the magnitude (>13 km) and the danger of dispersal movements. It also indicates the potential of modern GPS technology for studying turtle movement and points toward the need for further studies with more individuals over longer timeframes.



Wood turtle, Glyptemys insculpta, Movement ecology, Continuous-time movement modeling, GPS