SAN JUAN, Puerto Rico (AP) — A critically endangered Puerto Rican toad was for the first time born via in vitro fertilization as U.S. scientists attempt to save it from extinction, officials announced Friday.

Olaf – named in honor of the frozen semen he came from — is the first of more than 300 Puerto Rican crested toads that hatched after the first attempt failed, Diane Barber, ectotherms curator at the Fort Worth Zoo in Texas, told The Associated Press.

“We don’t typically name our toads, but that one deserved special recognition,” she said via phone. “We were super, super excited. … You kind of hold your breath for 30 days to see if they’re going to metamorphose.”

Barber was part of a team that traveled to the southwest town of Guayanilla last year to collect semen from six male Puerto Rican crested toads that were later released back into the wild. The scientists were careful to select bigger toads that had what are called “nuptial pads” on their thumbs, which indicate sexual maturity and help them grab on to females, she said.

Extracting semen from toads that measure up to 4.5 inches (11 centimeters) long is normally easy: they release it in their urine, and they usually pee whenever they’re picked up, Barber said. But for those toads that did not pee, another tactic was used.

“It’s kind of weird, but if you hold them in your hand and look at them and bark at them like a dog, they will pee,” she said.

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