"In my 24 years in the zoo business, this is one of the most exciting periods I've been through so far," says Jeff Ettling, curator of herpetology and aquatics at the Saint Louis Zoo.

He's talking about the birth of 185 baby Ozark hellbender salamanders (Cryptobranchus alleganiensis bishopi) at the zoo's Ron Goellner Center for Hellbender Conservation, which has a dozen or so additional eggs ready to hatch. It's the first time that Ozark hellbenders have ever been bred in captivity.

The news—announced last week by the center and the Missouri Department of Conservation—comes just two months after the U.S. Fish and Wildlife Service (FWS) finally protected the amazing but increasingly rare 60-centimeter-long amphibians under the Endangered Species Act. After decades of population declines due to pollution, the illegal pet trade, and now the amphibian-killing chytrid fungus, FWS estimates that there are just 590 or so of these creatures left in the wild. North America's largest salamanders, Ozark hellbenders live exclusively in the rivers and streams of northern Arkansas and southern Missouri.

The zoo and its partner agencies—including the FWS, the Missouri DOC and the Arkansas Game and Fish Commission, along with three universities—have been working to conserve Ozark hellbenders for more than a decade. They have collected both live hellbenders and wild-laid eggs to create a captive breeding and head-start program that allows juvenile salamanders to grow up safely without becoming bird or fish food. The first captive-laid eggs were produced at the zoo in 2007, but they were not fertilized.

One factor that may have helped this year's breeding success is the unique artificial habitats created at the zoo, which include two outdoor streams—each 12 meters long and 1.8 meters deep—which are lined with natural gravel and large rocks where the salamanders can hide. The streams also contain artificial nesting boxes—modeled after similar structures used in Japan to help conserve the even larger Japanese giant salamander (Andrias japonicus)—which is where the fertilized eggs were discovered. The zoo also maintains two climate-controlled rooms which mimic natural precipitation and lighting.

"A lot of zoos tried to breed hellbenders in a standard aquarium," Ettling says. "I think it boiled down to giving them a lot of space." The artificial streams give adult hellbenders plenty of room, as well as their choice of nest rocks and artificial nesting boxes where they can feel comfortable laying their eggs. "We've also learned a lot about water quality over the past decade. We're trying to mimic what we see in nature." He says the zoo maintains water pH, conductivity and ion content to make it more like the river water in the hellbenders' natural habitat. They also now have enough salamanders (including 23 males and 19 females in the zoo's potential "breeding nucleus") so that the females have more mating partners to choose from.

After finding the fertilized eggs in October, the zoo took about three quarters of the clutch out of the stream and left the rest with the male. "He was very defensive when we went to take the eggs out, which is good behavior," Ettling says. Hellbender males stay with their nests and are very defensive of their young in the wild. The original plan was to observe the difference between the eggs the male protected and the ones the zoo cared for, but they ended up pulling the remaining eggs because the artificial stream was too large and any young that hatched would be too difficult to monitor. "We wanted to be able to raise them in a more controlled environment."

The eggs were placed into a special tray system—seen in this video—which allowed the zoo to control water flow, temperature and oxygen levels. "When a male hellbender is under a rock, the water doesn't have as much flow and therefore has less oxygen," Ettling says. "The male compensates for that by rocking back and forth, which increases his oxygen intake and continuously jostles his eggs around." The zookeepers got their hands wet to replicate this process. "We put on surgical gloves and moved the eggs around every couple of days. That will be part of our protocol from now on."

Now that all but the last few of the eggs have hatched, the baby hellbenders will spend their next several years at the zoo. "What we're going to try to do is raise these animals to six to eight years of age before releasing them back into the wild, which will give them a fighting chance of survival," Ettling says. "At that size, they adapt well and should be able to set up their own home ranges."

Meanwhile, the zoo will continue its efforts to conserve and breed its other hellbenders. "Right now, we have as many hellbenders in captivity as are in the wild," Ettling says. "If we can double or triple that in the next couple of years, that's a good place to be."

Previously in Extinction Countdown: "Hellbender Salamander Gets Endangered Species Designation, but No Habitat Protection—and That May Be a Good Thing"

Photos: Hellbenders in eggs by Mark Wanner courtesy of Saint Louis Zoo. Adult hellbender by Jill Utrup via the U.S. Fish and Wildlife Service