Got Nature? Blog

Spring time brings a cacophony of frog calls around ponds and wetlands, but as spring slowly transitions into summer, the warmer temperatures signal the breeding season for many of our native reptiles. One of the oldest and most primitive reptile groups are the turtles. These ancient reptiles have remained relatively unchanged for 225 million years. There are currently ~300 species of turtles worldwide, and 18 species are found in Indiana. Most turtles in Indiana are associated with water, particularly waters that provide a variety of food items, basking sites and adjacent upland habitats. While Indiana is home to a diversity of turtle species, many are declining in number across their range. There are many factors contributing to these declines, but one that is particularly important this time of year is road mortality.

Figure 1: Small pond containing semi-aquatic turtles with a major road intersecting adjacent breeding habitat.

Why do you see so many turtles crossing the road in late spring and early summer (May-June)? This is the time of year when most of our turtles are searching for adequate nesting sites. Unlike amphibians that generally lay their eggs directly in the water, female turtles search for nesting spots in open, unshaded areas where the soil is not muddy or subject to flooding. Nests are often located on the nearest spot of land providing these conditions, but females of some species may travel 1-2 kilometers in search of a suitable net site.

Figure 2: Female Red-eared Slider killed while attempting to cross the road to lay eggs at nearby upland nesting site.

Unfortunately, many of the upland sites are separated from ponds, lakes and streams by roads (Figure 1). As the females leave the ponds to lay eggs, they are forced to cross busy roads and may suffer incredibly high mortality rates (Figure 2). Females are more prone to road mortality than males (which are not required to leave the water to lay eggs), resulting in some populations consisting of nearly all male turtles. Increased female mortality lowers population growth rates (once the female is killed, so are the eggs she was carrying). To further complicate matters, turtles are long-lived species (up to 100 years), and females may not reach sexual maturity for 8-25 years.

What can you do to help? Increase vigilance and slow down when driving, especially in areas where roads intersect ponds and adjacent uplands. If you encounter an injured turtle that needs medical attention, call the Indiana DNR at 800-893-4116 or 317-232-4080 during business hours, 765-473-9722 (northern half of Indiana) or 812-837-9536 (southern half of Indiana) after hours or visit wildlifehotline.info.

For more information on turtles:
The Turtles of Indiana
The Education Store (Search keywords for more information)

Rod Williams, Associate Professor of Wildlife Science
Department of Forestry and Natural Resources, Purdue​ University