Helping Endangered Blanding’s Turtles Survive at Brookfield Zoo

—by Bill Zeigler, senior vice president of collections and animal care for the Chicago Zoological Society/Brookfield Zoo and member of the Board of Directors for the Turtle Survival Alliance

You may never have seen a Blanding’s turtle because they are endangered in Illinois and threatened nationwide. That is why the Chicago Zoological Society, which manages Brookfield Zoo, has collaborated with the Forest Preserve District of DuPage County to create a breeding and release program that includes a new outdoor turtle habitat at Brookfield Zoo.

The project has two goals: to provide a higher number of Blanding’s turtle hatchlings for release and to improve conditioning techniques for hatchlings that will be released. Hatchlings resulting from the program either will be immediately released in DuPage County forest preserves or will grow for two years in a predator-proof area at the zoo’s Dragonfly Marsh exhibit.

Blanding’s turtles in the wild have about a 2 percent chance of reaching breeding maturity due to the number of challenges they face while maturing. For example, an increase in the number of raccoons and other Blanding’s turtle predators in Chicagoland depletes the population.

Also, turtles that are raised by people before being released in the wild lose their fear of people and become more exposed to illegal collecting. Plus, they have a lower survival rate than wild turtles do. To counter this, our staff is taking important precautions to condition the turtles for their release. For example, the hatchlings are placed in large outdoor enclosures instead of water tubs. This allows the hatchlings to forage on their own for food sources, such as snails, slugs, and small fish. While food is supplemented, the turtles hunt for it and are not handled.

CZS has also developed a new off-exhibit breeding area that reflects Blanding’s turtles’ natural habitat. The species is a wetland turtle and requires a marshy water area as its main habitat, however, females lay eggs in upland areas. The pond at the zoo provides both types of terrain to encourage breeding, and the space will eventually house 30 to 40 female turtles.

Recently, the Forest Preserve District of DuPage County gave CZS nine subadult Blanding’s turtles that were released into the off-exhibit pond to eventually mate and, hopefully, produce offspring that will increase their numbers in the wild. We estimate that the turtles could produce 250 to 300 hatchlings per year.

This fall, CZS will return 12 Blanding’s turtles that have been in the predator-proof enclosure at Dragonfly Marsh to DuPage County to help bolster the population in the preserves.

Blanding’s turtles can live upwards of 80 or 85 years but do not reach sexual maturity until roughly 13 to 15 years of age. After the release of these turtles this fall, additional releases will continue with turtles bred at the zoo.

Fostering a sustainable population is an important step to increase the Blanding’s turtle population locally and allow this species not only to survive but also begin to thrive. At CZS, we are committed to the highest level of animal welfare, including that of specimens that are conditioned for release programs. That is why this program is so important.