Detroit Zoo Sends 6,855 Tadpoles to Save Puerto Rican Toads

The Detroit Zoo recently packed up 6,855 tadpoles and sent them on a mission to save an entire species in Puerto Rico.

The tadpoles, bred at the zoo's specialized amphibian center, will be released into Rio Encantado rainforest in Manati, where they'll grow into Puerto Rican crested toads. This critically endangered amphibian is found nowhere else on Earth.

"Each of these tadpoles represents a lot of care, coordination and hope," said Mark Vassallo, curator of amphibians for the Detroit Zoological Society. His team has now sent 143,195 tadpoles to Puerto Rico since joining this conservation effort.

The program started in the 1980s, making it the longest-running amphibian reintroduction program in the world. Wild populations have fluctuated between just 300 and 3,000 individuals over the past three decades, mostly concentrated in areas vulnerable to hurricanes and droughts.

The toads face serious threats from invasive species like marine toads and Cuban tree frogs, plus predators including feral cats, dogs, and mongoose. Habitat loss has made their situation even more precarious since they rely on temporary freshwater pools to breed.

The Detroit Zoo's process takes three to four months of creating ideal wild conditions for breeding. In early May, carefully selected breeding pairs produced this latest batch of tadpoles, which were shipped to the island about a week later.

The Ripple Effect

Once the tadpoles arrive in Puerto Rico, they metamorphose in less than two weeks. From the size of a dime, they'll grow into palm-sized adults weighing about 50 to 60 grams with a lifespan of roughly five years in the wild.

These tiny toads play an important role in Puerto Rico's native biodiversity and ecosystem health. Every tadpole released strengthens wild populations and helps maintain the delicate balance of rainforest habitats.

The Detroit Zoo is one of only two U.S. zoos with a dedicated amphibian center separate from reptiles. Visitors can see more than 50 Puerto Rican crested toads in a biosecure exhibit while learning about conservation efforts happening half a world away.

The work connects communities across continents. Detroit residents supporting their local zoo are directly helping protect endangered species in Puerto Rico, showing how local action creates global impact.

Nearly 7,000 tadpoles might seem small, but they carry the weight of an entire species' future on their tiny backs.