Wood Turtle

Wood Turtle

Glyptemys insculpta

The wood turtle is an extraordinary North American species that is increasingly threatened by habitat loss and human encroachment. Smithsonian scientists are tracking them to shed new light on their movement within and between populations fragmented­ by agriculture and development.

Facts

Length: 18-23 cm (7 to 9 in)

Weight: 900-1400 g (2 to 3 lbs)

Conservation Status: Endangered

Wood turtles spend the cold winter months hibernating in fast-flowing streams, emerging to feed and thermoregulate on land during warmer months.

Unfortunately, wood turtles are often illegally poached for the pet trade.

Wood turtles exhibit a behavior not observed in any other reptile: the worm stomp. This involves stomping their feet and shell on the ground to imitate falling rain or the movement of moles, tricking worms into coming to the surface where they can be eaten.

Tracking

Wood turtles are a very long-lived species with a slow reproductive strategy. Although few hatchlings will survive to maturity, those that do can reproduce for decades with few natural predators. This means that wood turtle populations are particularly hard hit by modern threats such as cars, agricultural machinery, and illegal poaching. With landscapes rapidly changing around them, wood turtle populations are increasingly fragmented, often disappearing entirely with suburban encroachment. This has led to a rapid decline in numbers over the past several decades.

To combat this decline, Smithsonian scientists have been closely monitoring wood turtle populations since 2011 and have been tracking individuals since 2016. With the recent miniaturization of GPS technology, scientists are able to attach tracking devices that weigh less than half an ounce, allowing them to collect detailed movement data. Over the past three years, 36 individual turtles have been tracked in this way.

The tracking information these GPS units collect is being used to understand how wood turtles move across and use the landscape throughout the year. Critically, it has shed light on previously undocumented dispersal movements. Smithsonian scientists have found that these relatively small turtles are making enormous movements (ca. 13 miles), presumably in search of new feeding and breeding opportunities. Unfortunately, these long-distance movements can put turtles at great risk, as their paths cross busy roads, active farm fields, and suburban areas. By better understanding where, when, and how far these turtles are moving, Smithsonian scientists seek to broaden the scale and improve the effectiveness of conservation efforts aimed at saving this incredible species.

Wood turtles pose significant challenges to monitoring them due to their small size. To avoid overburdening the turtles, scientists use lightweight GPS units initially designed for birds. These units are only a couple inches long and weigh a mere 10g (< 0.5 oz), meaning they have a much shorter battery life than GPS collars made for larger animals. This means that scientists must frequently replace the GPS units to keep their batteries from dying. Every couple of weeks, each turtle is manually tracked using a handheld radio antenna tuned to the frequency of a transmitter device attached to the turtle’s shell. This process can present its own challenges, since turtles are often underwater or hidden under leaves on the forest floor. Once a turtle has been located, its GPS unit is removed from inside a specially-made PVC sheath on the back of their shell and replaced with a fully charged unit. The PVC sheath and radio-transmitter are attached using a gel epoxy while the GPS units themselves are held in place with zip-ties.

Another challenge is presented by the semi-aquatic lifestyle of wood turtles. Because GPS signal is unable to travel through water, units attached to the turtles are unable to record locations over winter months when wood turtles hibernate in streams to avoid freezing air temperatures. Locations during this period must be obtained manually by radio-tracking the turtles and recording coordinates using hand-held GPS units.

Meet the Team

Tom Akre, Ph.D.

Program Scientist
Working Land and Seascapes
Conservation Ecology Center
Smithsonian Conservation Biology Institute (SCBI)
National Zoological Park

Jonathan Drescher-Lehman

Smithsonian Mason School of Conservation
George Mason University & Conservation Ecology Center
Smithsonian Conservation Biology Institute (SCBI)
National Zoological Park