A toast to tadpoles: Brookfield Zoo Chicago reaches historic milestone with 12,244 new toads

Brookfield Zoo Chicago has reached a major conservation milestone by successfully breeding and raising 12,244 Puerto Rican crested toad tadpoles for release into the wild, according to an announcement. The total is the largest from a single breeding cycle at the Chicago-area facility and adds to nearly 40,000 tadpoles the zoo has contributed over the past decade.

The effort supports island-wide recovery work led by the Puerto Rican Crested Toad Conservancy, in partnership with the Puerto Rico Department of Natural and Environmental Resources, the U.S. Fish and Wildlife Service, and 16 accredited zoos and aquariums, according to Brookfield Zoo in Chicago.

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Why the toad matters

The Puerto Rican crested toad is the only toad native to Puerto Rico and was once thought to be extinct in the wild, according to the announcement. It remains listed as endangered by the International Union for Conservation of Nature, threatened by the U.S. Fish and Wildlife Service, and endangered by Puerto Rico’s natural resources department.

Brookfield Zoo in Chicago said the species faces threats from habitat loss, invasive species, rising sea levels, and saltwater intrusion into breeding wetlands. Southwestern Puerto Rico’s Guánica Commonwealth Forest has the last naturally occurring population, the press release confirms.

Care, timing, and release

Zoo staff said the breeding process is timed to Puerto Rico’s rainy season, when conditions are best for survival after release. The work includes selecting breeding pairs to support biodiversity, simulating seasonal changes, and hand-counting the tadpoles before they are transported to Puerto Rico.

Once there, the tadpoles are placed in managed aquatic habitats and monitored through metamorphosis before they disperse into the surrounding landscape, according to the zoo.

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Mike Masellis, Brookfield Zoo Chicago's lead animal care specialist, said in the press release, “Conservation work like this can be incredibly detailed and time-consuming, but that’s what makes these milestones so meaningful. From carefully coordinating breeding pairs to hand-counting thousands of tadpoles and tracking toads in the field, every step plays an important role in helping restore this species.”

He added, “Our hope is that years from now, some of these tadpoles will return to the breeding ponds as adults and continue establishing future generations in the wild.”

Two zoo specialists traveled to Puerto Rico last fall to monitor toads at a release site and study habitat use, predator pressures, and environmental conditions, according to Brookfield Zoo in Chicago.

The zoo currently cares for about 20 Puerto Rican crested toads, mostly behind the scenes, and earlier this year, two were placed on view in The Swamp. Guests can learn more at the zoo and through its conservation content, according to Brookfield Zoo in Chicago.