Habitat selection, movement, and food preferences of Wood Turtles (Glyptemys insculpta) in an agri-forested landscape

Wood Turtles (Glyptemys insculpta (Le Conte, 1830)) can use agricultural fields for basking and feeding, but hayfields can be an ecological trap due to mortality associated with agricultural machinery. It is unclear if hayfields are selected habitat or simply occur adjacent to used waterways. We sought to investigate Wood Turtle habitat selection at the third- and fourth-order scales in an agri-forested landscape and quantify food abundance (berries, fungi, and gastropods–worms) among habitat types. To quantify habitat selection by Wood Turtles, we radio-tracked 23 adults from May to November of 2018. We measured habitat features at each turtle location and three random sites within 50 m. At the third order, turtles primarily selected for edge habitat and selected hayfields over forest. At the fourth order, turtles selected for low canopy cover and presence of woody debris. Earthworms (suborder Lumbricina) were abundant within hayfields, and berries and fungi were abundant in forests. Turtles abandoned hayfields at the end of July, likely due to the emergence of food within the forest. Food availability likely influences their habitat use during the season, and hayfields provide a food source that entices Wood Turtles during the prime hay harvest period, which likely increases the risk of machinery-related mortality.

Passive transport of Eastern Elliptio (Elliptio complanata) by freshwater turtles in New England

Dispersal of freshwater mussels (order Unionida) is primarily as glochidia on the fins and gills of host fish. Adult mussels are more sessile, generally moving short distances (<2 m/week) along lake and river beds. Between 2007 and 2016, we observed seven instances of adult Eastern Elliptio (Elliptio complanata) and one instance of a fingernail clam (Sphaerium sp.) attached to the feet of freshwater turtles in streams and ponds of New England, United States. Observations included five instances of mussels attached to Wood Turtles (Glyptemys insculpta) in Maine and Massachusetts, one instance of a mussel attached to the fingernail of an Eastern Painted Turtle (Chrysemys picta) in Massachusetts, one instance of a mussel attached to a Snapping Turtle (Chelydra serpentina) in Massachusetts, and one instance of a fingernail clam attached to the fingernail of an Eastern Painted Turtle in Massachusetts. We suggest that Eastern Elliptio may be susceptible to transport by freshwater turtles foraging in mussel beds and that transport of adult mussels by freshwater turtles could result in otherwise atypical long-distance, upstream, or overland dispersal between waterbodies.

GPS Technology for Semi-Aquatic Turtle Research

Global positioning system (GPS) telemetry units are now small enough to be deployed on terrestrial and semi-aquatic turtles. Many of these GPS units use snapshot technology which collects raw satellite and timestamp data during brief periods of data recording to minimize size. We evaluated locations from snapshot GPS units in stationary tests and on wood turtles (Glyptemys insculpta) in northeastern Minnesota. Stationary GPS units were placed in wood turtle habitat to evaluate location accuracy, fix success rate, and directional bias. The GPS fix success rate and accuracy were reduced in closed canopy conditions and when the stationary GPS unit was placed under a log to simulate wood turtle hiding behavior. We removed GPS location outliers and used a moving average calculation to reduce mean location error in stationary tests from 27 m (SD = 38) to 10 m (SD = 8). We then deployed GPS units and temperature loggers on wood turtles and collected 122,657 GPS locations and 242,781 temperature readings from 26 turtles from May to September 2015 and 2016. Location outliers accounted for 12% of locations when the GPS receiver was on a turtle. We classified each wood turtle location based on the GPS location and by comparing temperature profiles from river, sun, and shaded locations to the temperature logger on the turtle. We estimated that wood turtles were on land 68% (SD = 12) of the time from May to September. The fix success rate for land locations was 38% (SD = 9), indicating that wood turtles often use habitats with obstructed views of the sky. Mean net daily movement was 55 m (SD = 192). Our results demonstrate that snapshot GPS units and temperature loggers provide fine-scale GPS data useful in describing spatial ecology and habitat use of semi-aquatic turtles.

Fine- and coarse-scale movements and habitat use by Wood Turtles (Glyptemys insculpta) based on probabilistic modeling of radiotelemetry and GPS-telemetry data

Understanding animal movement and habitat use is critical for the delineation of habitat requiring protection for species at risk. Defining critical habitat requires studies with observations at a fine enough scale to reflect how animals use and move among habitats and include enough individuals to generalize findings to the population. We present results of a multiyear study on 48 adult Wood Turtles (Glyptemys insculpta (Le Conte, 1830)) from two different populations monitored with low-frequency radiotelemetry and high-frequency GPS telemetry. Results demonstrated the propensity for conventional radiotelemetry to underestimate cumulative distances moved and overestimate the amount of habitat used by Wood Turtles. Together the two data sets demonstrate the propensity for Wood Turtles to remain in close proximity to the river and that some differences in habitat use occur between the sexes; males tended to move parallel to the river, whereas females moved perpendicular to the river. The GPS-telemetry data provided a robust spatiotemporal data set that provided a better understanding of frequently used habitat types and features. Overall, study results suggest that currently delineated areas of protected habitat are likely to be effective in conserving these two populations and provides significantly improved, spatially explicit knowledge that can be used to inform further mitigation efforts if necessary.