By Roy D. Nagle, Director Of Environmental Health & Safety, Juniata College
Northern Map Turtles are a long-lived riverine species of conservation concern with a limited distribution in Pennsylvania.
In a recent issue of the Journal of Herpetology, my colleagues and I from Juniata College, Huntingdon, and the University of Maryland’s Chesapeake Biological Laboratory report a high incidence of abnormal shell shapes in Northern Map Turtles of the Juniata River.
Turtles with morphological abnormalities may be living environmental indicators and serve as historical records of developmental threats and injuries to other animals.
Our research examined the morphology of turtles at Mount Union, a former industrial site and the largest known turtle nesting area in central Pennsylvania.
Among 535 adult female turtles, 29 percent exhibited abnormal shell shape, often in the form of an indentation in one or both sides of the carapace. Older females had a higher incidence of abnormalities than younger females.
No shell shape abnormalities were observed among 703 hatchlings collected from nests, and no shell shape abnormalities were observed among seven of those marked hatchlings that returned to Mount Union as 11–18 year old adult females to nest.
Historically, most of the nesting substrate at Mount Union consisted of black coal tailings, which exposed developing embryos to high temperatures and potential chemical insults.
In addition, a large area contaminated with creosote is present near the turtle nesting area and the Juniata River. A variety of developmental deformities in turtles have been associated with creosote contamination of wetlands in other locations.
The high incidence of abnormal carapace shapes of adult female Northern Map Turtles at Mount Union may reflect a delayed response to chemical or thermal conditions encountered in the nesting substrate, direct exposure to contaminants in the Juniata River as sub-adults, or factors that affected turtles a generation ago but have since abated.
Click Here for a copy of the research paper.
To learn more about amphibians and reptiles in Pennsylvania, visit the PA Amphibian and Reptile Survey website.
(Photo: Carapaces of adult female Northern Map Turtles (Graptemys geographica) from Mount Union, Pennsylvania. Shell shape abnormalities include: (A) both sides, (B) flared posterior marginal scutes, and (C) both sides as well as flared posterior marginal scutes. Blue paint codes on turtles allow identification of individual nesting females from a distance. The turtle in (D) with normal carapace shape was marked as a hatchling, released into the Juniata River, and recaptured during 2017 as an 11-year old reproductive adult female. )
Editor: Roy Nagle, is Director of Environmental Health and Safety in the Department of Environmental Science at Juniata College. He is an environmental scientist specializing in herpetology and has studied the long lives of turtles for more than 30 years. He can be contacted by sending email to: nagle@juniata.edu or call 814-641-3555.
His research includes one of the longest continuous studies of freshwater turtles at the University of Michigan’s E.S. George Reserve, and studies of Box Turtles, Map Turtles, and Wood Turtles in central Pennsylvania.
He has worked with the Pennsylvania Department of Transportation, the Department of Conservation of Natural Resources, the Pennsylvania Fish and Boat Commission, and the U.S. Army Corps of Engineers to protect critical habitats and promote the conservation of freshwater and terrestrial turtles.
Nagle and his colleagues seek additional support to continue their research at Mount Union and help conserve Northern Map Turtles in Pennsylvania.
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