Since 2012, the Toronto Zoo has functioned as a kind of turtle daycare. That’s when it introduced a new program for the Blanding’s turtle, a species that’s classified as threatened in Ontario.
Turtles born there stay for two years — they’re released when they reach the size of a baked potato. The zoo released its first batch of turtles in 2014: this year it harvested and incubated 130 eggs.
The practice is known as captive breeding, and it can play a key role in preventing species from going extinct.
“Ultimately, why we do it is to get them to grow bigger in a safe, protected environment so that when we release them they're at a bigger size,” says Katherine Wright, coordinator of the Toronto Zoo’s Adopt-a-Pond program.
The Ministry of Natural Resources collects eggs from areas where the adult population is doing well but young hatchlings stand little chance of surviving — on the shoulder of a road or in a farmer’s field, for example. The zoo relies on eggs harvested from the Brantford area, which is home to a self-sustaining population.
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Every turtle is outfitted with a locator backpack, allowing researchers to track their survival — as the program is still new, it’s difficult to assess its impact.
But there are clear suggestions that captive breeding can make an important difference. In the case of the endangered loggerhead shrike, for instance, it bought researchers valuable time to try to help the species survive. The tiny songbird, which impales its food — typically mice and large bugs — on thorns before picking it apart with a razor-sharp beak, is considered endangered in Ontario. Breeding programs are in place in the province at the Toronto Zoo, the African Lion Safari, and the Mountsberg Raptor Centre.
“It's definitely having an impact. In 2016 and 2017, we did see increases both years in the wild population,” says Hazel Wheeler, coordinator of Wildlife Preservation Canada’s eastern loggerhead shrike recovery program. “Up to 30 per cent of the birds that we found on the landscape had come from the conservation breeding program.”
Researchers first took notice of the serious decline in shrike population in 1997, when there were only 18 pairs in the wild.
“The captive-breeding program has certainly had a stabilizing effect on the population. It's a bit early to say whether it's reversed the trend. Each year, we wait and see what happens,” says Wheeler.
Researchers don’t have solid information about where the birds migrate to and suspect that some of the deaths occur in its wintering grounds. All of the captive-released birds are radio tagged, though, which could provide clues as to where they go during the colder months. There have been reports of banded birds in Virginia and Delaware, and researchers have formed a binational group with American partners to try to help the bird.
“Without the captive breeding program, the shrikes would maybe not entirely have disappeared yet, but they'd certainly be much worse off,” says Wheeler. “The thing you need to do with each species is to identify the main threats. Habitat loss is always a big one — but with loggerhead shrikes we don't have any kind of silver-bullet answer about what is absolutely causing these declines.”
Captive breeding is only one piece of the conservation puzzle — at-risk species face pressures in the environment that will remain no matter how much the population is replenished. But it does allow populations to stay stable or recover slightly while other work is underway.
The Toronto Zoo, for example, is also restoring the Rouge Valley breeding areas of the Blanding’s turtle and working to preserve its habitat.
“It's not good releasing them into the wild if there's no habitat there for them,” says Wright.