Researchers Find Giant Tadpole ‘Larger Than a Coke Can’ After Draining Swamp

May 20, 2019 Updated: May 26, 2019

Think back to grade school biology class and you may recall how tadpoles, those tiny, tailed swamp-dwellers, transform into frogs.

First, they lose their tails, then they sprout legs—all in a process called  metamorphosis.

Well, in a pond in the Chiricahua Mountains of Arizona, scientists found a giant tadpole many times larger than your typical tadpole. Having never lost its tail, having never sprouted legs, nor turned into a frog, it just kept growing, and growing, and growing.

The massive polliwog has broken all previous size records for its species of bullfrog. End to end, the monster specimen is a full 10.1 inches long (257 mm), and its circumference is larger than a coke can! They gave the tadpole a fitting name: Goliath.

The group of biologists had been draining the man-made swamp as part of a habitat restoration project for the endangered Chiricahua leopard frog.

Intern volunteer Alina Downer, from the Natural History Southwest Research Station (SWRS), was wading in the knee-deep mud, about the consistency of “chocolate soup,” they explained. They were assessing what organisms remained, fishing about with their hands, when something big bumped into her leg.

“At first I thought it was a giant catfish,” Downer told American Scientist. “Whatever it was, I knew I had to grab it.”

She “felt something large, smooth, and wriggly.” It was so large that she had to herd it to shallower waters and use both hands to hold the humongous bullfrog polliwog.

It’s unclear how old Goliath the tadpole is; most tadpoles live for around two to three years before turning into adult frogs. Goliath kept his tail and did not sprout legs; his fish-like mouth does not resemble a frog’s mouth. The researchers speculated that certain developmental hormones may be “turned off.” It’s unclear whether Goliath’s growth outpaced his cohorts or if he was left behind as a tadpole after they metamorphosed.

“I’m guessing that this guy will never transform into a frog,” said David Pfennig for the University of North Carolina.

Goliath has inspired much interest at the station. “I’m curious if it’s going to keep getting bigger, and what the life span will be like,” said Downer. Goliath’s growth has slowed since being captured, they noted. Now, they plan to take tissue samples and study his history and genetics. They continue feeding the giant his favorite algae and monitoring his development.

And in the meantime, there are plenty of photo opportunities for admiring researchers to indulge in with the polliwog.