Nearly 3,000 Ozark hellbender eggs laid by eight females mark the second time the endangered amphibian has been bred in captivity at the St. Louis Zoo.
"That's an incredible number," lead hellbender keeper Chawna Schuette of the Saint Louis Zoo said. "That's more than I could have ever imagined. It's exponential success."
Last year, the zoo was able to hatch 185 of the salamander eggs. Since then, they have learned new techniques to increase the number of eggs that hatch, such as physically stimulating them to give them exercise.
"We literally rock the babies three times a day now," Schuette said.
The Ozark hellbender is one of the largest salamanders in North America and was listed as an endangered species in 2o11. Less than 600 exist in the world, after reaching a peak of more than 8,000 in south-central Missouri and Arkansas.
This is the first time hellbenders from all three rivers they were collected from have produced eggs. Two clutches of the eight clutches came from Eleven Point River Ozark hellbenders. Three of the clutches each came from the Missouri's Current River and the North Fork of the White River. Hellbenders from the North Fork have been in captivity indoors for the past eight years.
The 2,809 fertile eggs were laid in two, 40-foot-long artificial streams that were built in 2004 with funding from the zoo, the Missouri Department of Conservation and the U.S. Fish and Wildlife Service — all partners in the project.
Of these fertile eggs, more than 300 have hatched into larvae. Schuette is expecting about 2,600 of the 2,800 to hatch in December.
"It's a nice problem to have, but wow," she said.
The hellbenders will be released when they are between the ages of 3 and 8. Schuette said it would be preferable to keep them in captivity longer. Studies have showed the bigger they are when they are released, the more likely they are to survive.
Because it has to house and feed so many hellbenders, the zoo might release some at 3 years old at about 6 inches and then hold some until they are 8 years old, when they would be about a foot long and approaching reproductive age.
"The bigger they are when they're released, the higher their survivor rate," Schuette said. "Before we were so successful, we were hoping to keep them a bit longer."
Supervising editor is John Schneller.