D. A. Steen¹, M. J. Aresco², S. G. Beilke³, B. W. Compton⁴, E. P. Condon¹, C. Kenneth Dodd Jr.⁵,
H. Forrester⁶, J. W. Gibbons⁷, J. L. Greene⁷, G. Johnson⁸, T. A. Langen⁹, M. J. Oldham¹⁰,
D. N. Oxier¹¹, R. A. Saumure^12*, F. W. Schueler¹³, J. M. Sleeman¹⁴,
L. L. Smith¹, J. K. Tucker¹⁵ & J. P. Gibbs¹⁶

Affiliations
1 Joseph W. Jones Ecological Research Center, Newton, GA, USA
2 Department of Biological Science, Florida State University, Tallahassee, FL, USA
3 The Pacific Northwest Turtle Project, Portland, OR, USA
4 Department of Natural Resources Conservation, Holdsworth Natural Resources Center, University of Massachusetts, Amherst, MA, USA
5 USGS/Florida Integrated Science Centers, Gainesville, FL, USA
6 Turtle Rescue of New Jersey, Hardwick, NJ, USA
7 University of Georgia, Savannah River Ecology Lab, Aiken, SC, USA
8 Department of Biology, SUNY Potsdam, Potsdam, NY, USA
9 Department of Biology, Clarkson University, Potsdam, NY, USA
10 Natural Heritage Information Centre, Ontario Ministry of Natural Resources, Peterborough, ON, Canada
11 Arrowhead Reptile Rescue, Ohio Department of Natural Resources Wildlife Rehabilitation, Cincinnati, OH, USA
12 Department of Natural Resource Sciences, McGill University, Ste-Anne-de-Bellevue, Qué, Canada
13 Bishops Mills Natural History Centre, Bishops Mills, ON, Canada
14 Wildlife Center of Virginia, Waynesboro, VA, USA
15 Great Rivers Field Station, Illinois Natural History Survey, Brighton, IL, USA
16 SUNY College of Environmental Science and Forestry, Syracuse, NY, USA

Abstract
Recent studies suggest that freshwater turtle populations are becoming increasingly male-biased. A hypothesized cause is a greater vulnerability of female turtles to road mortality. We evaluated this hypothesis by comparing sex ratios from published and unpublished population surveys of turtles conducted on- versus off-roads. Among 38 166 turtles from 157 studies reporting sex ratios, we found a consistently larger female fraction in samples from on-roads (61%) than off-roads (41%). We conclude that female turtles are indeed more likely to cross roadways than are males, which may explain recently reported skewed sex ratios near roadways and signify eventual population declines as females are differentially eliminated.

 

Keywords
data synthesis; highways; nesting migrations; road mortality; reptile; roads; sex ratio; turtles

Correspondence
David A. Steen, Joseph W. Jones Ecological Research Center, Route 2, Box 2324, Newton, GA 39870, USA.
Email: David.Steen@jonesctr.org

*Current address
Research Division, The Springs Preserve, Las Vegas, NV, USA.