Courtesy Brookfield Zoo

Blanding’s turtles are endangered in Illinois and threatened nationwide, but the Chicago Zoological Society (CZS), in collaboration with the Forest Preserve District of DuPage County, is leading an initiative to increase the local wild population. The Society, which manages Brookfield Zoo, has created a breeding and release program that includes a new outdoor Blanding’s turtle habitat at the zoo’s Dragonfly Marsh exhibit. The program will allow CZS staff to develop and improve breeding and rearing techniques that will increase the number of turtles available for release. Later this fall, 12 turtles will be released in DuPage County forest preserves to help bolster the wild population.

“Our mission is to support the continued survival of the Blanding’s turtle in the Chicagoland area,” said Bill Zeigler, senior vice president of collections and animal care for CZS. He also serves on the board of directors for the Turtle Survival Alliance, an organization that works to protect turtles worldwide. “Fostering a sustainable population is an important step to increase the Blanding’s turtle population locally and allow this species to not only survive but, hopefully, begin to thrive.”

Blanding’s turtles in the wild have an approximate 2 percent chance of reaching maturity due to predators like raccoons and herons. Brookfield Zoo received a group of young Blanding’s turtles from the Forest Preserve District of DuPage County that will be housed at Dragonfly Marsh and will grow in the predator-proof area until ready for release. Typically, turtles that are raised by people before being released into the wild have an even lower survival rate than wild turtles do, but Brookfield Zoo is taking important precautions to condition the turtles for their release.

Unlike other rearing programs, the turtles will go through normal seasonal cycles by remaining outdoors all year at a small off-exhibit pond on the zoo’s grounds. This will help prepare them for life in various weather and temperatures and habitat changes. The space at the zoo replicates the turtles’ natural habitat and will be filled with native plants and logs. The turtles will forage on their own for food sources, such as snails, slugs, and small fish. While food is supplemented, the turtles will hunt for it and will not be handled.

“We are proud to work with Brookfield Zoo on this and champion the survival of Blanding’s turtles,” said Dan Thompson, ecologist for the Forest Preserve District of DuPage County. “Local wetlands, and the plant and animal ecosystem within them, improve our water quality and our understanding of the world around us.”
In addition to the planned release, Brookfield Zoo has created an off-exhibit breeding space for Blanding’s turtles that will house 30 to 40 female turtles in the future. The turtles there potentially could produce 250 to 300 hatchlings per year. The species is a wetlands turtle and requires a marshy water area as its main habitat; however, females lay eggs in upland areas. The space at the zoo will provide both types of terrain to encourage breeding.

The female turtles will be placed with males in smaller, separate ponds. Chicago Zoological Society staff will then collect the eggs and put them in incubators. The temperature at which the eggs are kept controls the sex of hatchlings: a higher incubation temperature produces males, while a lower temperature produces females. By controlling incubation temperatures, the zoo will be able to produce an even amount of male and female turtles. After the initial release of turtles this fall, additional releases will continue to occur with turtles bred at the zoo as the program progresses.

“We are committed to the highest level of animal care, and this breeding and release program is an opportunity to help a struggling population,” Zeigler said.

Blanding’s turtles can live to be upwards of 80 or 85 years but do not reach sexual maturity until roughly 13 to 15 years of age. This slow maturation is also coupled with the fact that Blanding’s turtles lay a small clutch of eggs—typically around 12 to 13 eggs at a time. Other turtle species, like snapping turtles, can lay as many as 60 to 70 eggs at once. Additionally, there has been an increase in the number of Blanding’s turtle predators—like raccoons—in the area, which further depletes the population. Another issue affecting Blanding’s turtles is that people continue to change and attempt to control water levels in many areas. Hatchlings require a marshy area with low water, and people alter the natural landscape, which can shrink or eliminate Blanding’s turtle habitats.