Thousands of Endangered Tadpoles Fly to Puerto Rico

More than 4,000 wiggling tadpoles conceived via wine fridges in California and then packed in a passenger plane headed to Puerto Rico this week as part of a program to re-establish a technicolor native toad once thought extinct. Since 2014, the Oakland Zoo has taken part in a campaign by North American zoos breeding the critically endangered Puerto Rico crested toad for release into protected ponds on the island, their ancestral home. Zoological manager Adam Fink used flight-tracking apps to monitor the 4,069-week-old tadpoles. They were traveling in double-bagged baggies topped up with oxygen. "Every single tadpole is important," Fink tells the AP.

The toads their hides a mix of brown, red, green, and yellow—thrived on Puerto Rico until sugar growers introduced a foreign toad they hoped would eat pests that feed on sugar cane. The introduced toad ate the native toad's young and took over its habitat. Biologists thought the crested toad had gone extinct, until a few survivors were found in 1984 and became the basis of the breeding program. At the Oakland Zoo, breeders use wine fridges to cool the adult toads to a state near hibernation, inducing them to breed, Fink says. (These California island foxes have made an amazing comeback.)