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Bog Turtle Conservation Work Continues at Great Swamp National Wildlife Refuge
Northeast Region, January 27, 2014
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2013 summer interns provided invaluable assistance with bog turtle conservation efforts. Pictured left to right: Christina Straway, Alyssa Frediani, and Rebecca Hiller.
2013 summer interns provided invaluable assistance with bog turtle conservation efforts. Pictured left to right: Christina Straway, Alyssa Frediani, and Rebecca Hiller. - Photo Credit: Colin Osborn/USFWS
Carapace (upper shell) view of two female bog turtles with radio-transmitters. The individual on the left is an old adult while the one on the right is a younger subadult. Note the difference in wear on their shells.
Carapace (upper shell) view of two female bog turtles with radio-transmitters. The individual on the left is an old adult while the one on the right is a younger subadult. Note the difference in wear on their shells. - Photo Credit: Colin Osborn/USFWS
Plastron (lower shell) view of the same two female bog turtles. Again, the  individual on the left is an old adult while the one on the right is a younger subadult. Note the light coloration down the middle of the subadult which is indicative of new growth.
Plastron (lower shell) view of the same two female bog turtles. Again, the individual on the left is an old adult while the one on the right is a younger subadult. Note the light coloration down the middle of the subadult which is indicative of new growth. - Photo Credit: Colin Osborn/USFWS
Volunteer Patricia Garvin admires two bog turtles that were found via radio-telemetry.
Volunteer Patricia Garvin admires two bog turtles that were found via radio-telemetry. - Photo Credit: Colin Osborn/USFWS
The bare red maples in the background were injected with herbicide capsules to maintain the open, sunny conditions that bog turtles rely on. The cattail and fern dominated foreground is one of the common habitat types that they prefer.
The bare red maples in the background were injected with herbicide capsules to maintain the open, sunny conditions that bog turtles rely on. The cattail and fern dominated foreground is one of the common habitat types that they prefer. - Photo Credit: Colin Osborn/USFWS

By Intern Alyssa Frediani and Fish and Wildlife Biologist Colin Osborn

 

The bog turtle (Glyptemys muhlenbergii) is North America’s smallest turtle, with a shell length of approximately 10 centimeters when fully grown. Newly hatched young (hatchlings) are about the size of a quarter and weigh as little as 3-4 grams. Their cryptic coloration makes them effectively invisible against the dark, mucky water they inhabit. Bog turtles were first discovered at Great Swamp National Wildlife Refuge in 1974 by Rutgers University researchers, the same year they were listed as a New Jersey state endangered species. Due to major reductions in range and numbers, in 1997 the bog turtle was listed as a federally threatened species. Given their rare status, staff began taking steps to protect and monitor the refuge’s small population.

Several different methods are used to monitor and manage the bog turtle population on the refuge: mark-recapture, radio-tracking, trapping, nest protection, and habitat restoration. Each new turtle that is found, either through visual surveys or through trapping, is marked with a unique number so that staff can identify it if it is captured again. Over the past decade, numerous bog turtles of varying ages have been found and marked on the refuge. Beginning in 2005 and then from 2009 to present, select adult and subadult bog turtles that were found were fitted with radio transmitters to monitor movement patterns and document important habitats used by these animals. In addition to visual surveys, trapping was conducted each year from 2009 to 2013 to see if new turtles could be found and previously marked turtles could be recaptured. While new individuals are important for estimating population size, recaptured turtles provide key information on long-term survival as well as the relative health of population. In 2012, movements of two radio-transmittered females were followed using a thread-spooling technique in order to find their nests. The two nests were protected and yielded a total of five hatchlings. Various habitat restoration efforts, such as eliminating invasive species like common reed (Phragmites australis) and reversing succession by reducing densities of red maples (Acer rubrum), have increased the amount of suitable habitat on the refuge.

This past year, refuge staff, interns, and volunteers tracked a total of five bog turtles (two adult males, two adult females and one subadult female). They were tracked every other week throughout the summer and fall until they entered hibernation. The subadult female had not been captured since 2010 and was an exciting find during the 2013 trapping effort. Many hours were put into habitat restoration during the summer and fall. Red maple saplings were cut and treated with herbicide and larger trees were injected with an herbicide lance. The red maples were eliminated so that core areas stay open, to allow turtles to bask, females to nest, and their eggs to incubate successfully. Maintaining open habitat is critical because if nests cannot hatch, there will be no new individuals entering the population. If this continues over time, the population will eventually die off.

Refuge staff plan to continue population surveys and radio telemetry work in 2014. Habitat restoration will remain a key component in helping to maintain viable populations. Visual and trapping surveys will be conducted on other areas of the refuge in order to see if bog turtles can be found on historic sites and potential sites that are being managed as suitable habitat. Nests will be protected as they are found, and staff will continue doing everything they can at Great Swamp National Wildlife Refuge in order to ensure the survival of this tiny and rare turtle species.


Contact Info: Colin Osborn, 973-702-7266 x15, colin_osborn@fws.gov



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