Brookfield Zoo and the DuPage County Forest Preserve District celebrated a day that was a decade in the making on Sept. 2 when they released 22 Blanding’s turtles into the wild in northwest DuPage County.
They were the first cohort of Blanding’s turtles – an endangered species in Illinois – released into the wild that were bred and hatched at Brookfield Zoo’s “head-start” program, which is a nearly decade-old partnership with the DuPage County Forest Preserve District.
Since 2011, DuPage County has provided Brookfield Zoo with wild-born juvenile turtles, which are raised in a predator-free pond at the zoo. But because it takes between 14 and 20 years for Blanding’s turtle females to reach reproductive maturity, last year was the first year any of the zoo’s 25 females laid fertile eggs.
“Nothing happens quickly with turtles,” said Andy Snider, curator of herpetology and aquatics at Brookfield Zoo.
Blanding’s turtles are native to the Great Lakes region, but can be found across a huge swath of North America, from Nova Scotia to Nebraska.
Snider said it’s hard to tell just how many Blanding’s turtles there are in Illinois, adding that their habitats tend to be small and scattered. Mobility has also decreased due to barriers like roads and increased development.
According to a press release, the survival rate of Blanding’s turtles in the wild is minuscule, with only about 2 percent reaching breeding maturity due to predators like raccoons. About 90 percent of turtle nests are destroyed by predators annually during the 60-day incubation period.
Brookfield Zoo’s head-start program gives the young Blanding’s turtles a better chance at survival, said Snider. In the spring, hatchlings are placed in protected outdoor pens at the Dragonfly Marsh habitat at Brookfield Zoo.
Snider says the young turtles get a taste of living in the wild, hunt for their own food while growing.
“When they’re released, they are considerably bigger than when they are put in there in the spring,” Snider said. “They have a much better shot at it [in the wild] than if they were a hatchling.”
The turtles released into the wild on Sept. 2 will also benefit the local population by reintroducing strains of DNA lost over time. Most of the breeding turtles at the zoo were the offspring of now-dead wild turtles.
“The offspring we’re releasing now are returning genetic information back to the wild population that may have been lost more than 20 years ago,” said Dan Thompson, ecologist for the DuPage County Forest Preserve District in a press release.
The Forest Preserve District started its first head-start program in 1996, collecting eggs from pregnant turtles found in the wild and then either caring for the eggs and hatchlings themselves or by partnering with other institutions, like Brookfield Zoo.
In all, the DuPage County Forest Preserve District has released more than 3,000 microchipped turtles from the head-start programs into the wild.
Snider said Brookfield Zoo plans to keep up its breeding program – more hatchings were born in 2020 than in 2019 and will be released into the wild next year – in the future. Female Blanding’s turtles can live up to 80 years and can lay fertilized eggs for decades.
“Now that the females are big enough, we should be getting more and more hatchlings per year,” Snider said. “I expect that trend to continue as the females mature. Whatever hatchlings we have here will go out into the wild every year.”