What the Heck Is a Hellbender—And How Can We Make More of Them?

Why the Saint Louis Zoo decided to invest in this slimy, surprisingly adorable amphibian

Ozark Hellbender-JTB2012.JPG
Meet the Ozark hellbender, an elusive creature that has become only more so as of late. Jeff Briggler

Jeff Briggler is leaning face-down in a freezing Missouri stream. Breathing through a snorkel and soaked up to his wetsuit-clad armpits, the Missouri resource scientist peers under rocks and probes into dark, underwater crevices. This is how you look for the rare, elusive survivors of the Carboniferous period, commonly known as hellbenders.

When he emerges, Briggler is holding a wriggling, pebbled and frankly adorable creature the size of a man's forearm. This slimy serpent is actually an endangered Ozark hellbender—though that modifier may be changing. The animal that Briggler drops into a blue mesh bag was born in captivity and has thrived in the wild against all odds, thanks to a series of conservation experiments by the Saint Louis Zoo.

Hellbenders were once common in the eastern United States, but there’s a reason you probably haven’t come across one. Both subspecies, the Ozark and eastern hellbenders, live exclusively in cool, fast-moving water and are sensitive to pollution and changes in habitat. They’re also notoriously elusive: Even people who spend their whole lives fishing and boating on rivers full of them rarely see one. They tend to hide in crevices or under rocks and aren't very active during daylight hours..

“I had never seen one in my life until I came on [as Missouri's state herpetologist] in 2000,” Briggler says. “I did a float on a river in 2000 and found my first one ... it was about 20 inches, it was a little scary because it's large. The two biggest things that jumped out at me were how flat its head was and for such a large animal how beady its eyes are.” In fact, hellbenders are the largest amphibian in North America, growing up to 30 inches long.

Briggler, an expert on native amphibians, commissioned a study to find out how the species was doing. The findings were sobering: About 50 years ago, there were something like 28,000 to 30,000 Ozark hellbenders in the wild. By 2006, the number dropped to a low of just 1,500. Humans are at least partly to blame: The rocks and crevices that hellbenders rely on are becoming filled in with sediment and silt from man-made runoff, leaving them with fewer places to hide and hunt.

“I immediately pushed to have hellbenders listed as an endangered species in the state of Missouri,” says Briggler, who lobbied within the Missouri Department of Conservation for their protection. “It was official in 2003 that both Ozark and eastern hellbenders were added to the state endangered list.”

What the Heck Is a Hellbender—And How Can We Make More of Them?
Hellbenders, the world's largest aquatic salamanders, can reach up to 30 inches long. Saint Louis Zoo

At the time, the future didn't look good for hellbenders. Three major obstacles stood in the way of their recovery. First, the main causes behind their sharp decline were poorly understood. Second, almost nobody other than scientists and fishermen had even heard of the things. And finally, nobody had ever managed to coax the species into breeding in captivity.

A partnership between the Missouri Department of Conservation with the Saint Louis Zoo began to turn things around on all three fronts.

The big idea, first proposed by the late hellbender-enthusiast and former director of animal collections Ron Goellner, was to build simulated Ozark streams in the zoo. He thought that by replicating the hellbenders' natural habitat as closely as possible, they might be able to coax them to start breeding. In 2004 the zoo built the first of three different 'raceways,' or artificial streams.

“We knew that space would be important,” says Jeff Ettling, curator of herpetology at the Saint Louis Zoo. “We knew that breeding them in an off-the-shelf aquarium wouldn't work. So we designed a system with 60 feet of moving water. We also built a couple of 40-foot streams. Each one of these streams has a specific genetic population.” Eight hellbenders were housed in each artificial stream, allowing females to choose which males to breed with.

In 2007, the first masses of hellbender eggs appeared in one of the artificial streams. But they failed to develop into baby hellbenders. It turned out the problem was the quality of the sperm, which was found to have bent tails and poor motility when viewed under the microscope. Nobody could figure out what was causing the deformed sperm until staff at the zoo started thinking about the hellbender eggs being more like fish eggs than like salamander eggs.

“We were going through some of the aquaculture literature and found that among fish, sperm production and then activation in the water is affected by ion concentration and dissolved solids,” Ettling says. “So we started reconstituting the water from scratch with whatever mineral concentration equaled that of an Ozark stream. Lo and behold, it worked.”

Looking at fish biology made a certain kind of evolutionary sense. Hellbenders are members of a very old family of salamanders which are somewhat similar to the first terrestrial vertebrates that left the water and began living on land. In evolutionary terms, they can help to illustrate the transition from fish towards diverse forms like dinosaurs, crocodilians and mammals.

The first captive-bred hellbenders hatched in 2011, and the zoo has produced more every year since. To date, 3,600 Ozark and eastern hellbenders have been released into the wild.

Because the threats to hellbenders vary from one place to another, scientists have been careful to release them at various ages and sizes. In case the little ones are being eaten by predators like bass or cottonmouth snakes, they mix in big ones. Or perhaps the smaller hellbenders are better able to escape some predators because they can hide in more numerous small crevices. Either way, researchers hedge their bets.

A key to the project's success is maintaining the hellbender genetics unique to a given stream. All of the adult hellbenders used for breeding in a particular raceway in a particular year were collected from the same waterway, and their offspring will only be returned to that waterway. While hellbender numbers were severely depleted throughout Missouri, they have only been 100 percent extirpated (or locally extinct) from one waterway, the Meramec River.

Briggler says that he found the remnants of that population barely in time to save them. “In the Meramec River... we have worked very hard to find brood stock. We've had four lonely males in one raceway for years, waiting [for females from that river to be found, to preserve their DNA]. We have one female now—something to start with.”

The traditional approach to captive breeding is reminiscent of the story of Adam and Eve: Identify one female and one male, place them in an enclosure together at the appropriate time of year, and wait for them to get down to business. This doesn’t always work. Zoos around the world have had enormous difficulty in getting captive elephants to reproduce—and don’t even get zookeepers started on pandas. The S Louis Zoo's doctrine may be a good one to follow: Simulate the wild environment, and allow animals to choose their own mates.

“I think it is going to be the wave of the future,” says Ettling. “It is going to be easier with smaller species because you don't need a lot of land. We need to get groups of animals together so they can make choices.”

The scientists know that the project is working because Briggler regularly finds released hellbenders in the wild. All of the released hellbenders have a tag embedded under their tails with an encapsulated bar code.

“When I'm out there, when I pick up one, I kind of have an intuition that is was a captive-released one,” says Briggler, who refers to himself on his profile page as "the Hellbender Whisperer." “Sometimes their color is a little different. I've seen thousands of hellbenders. I know where certain animals are each day. Which hole they are in, which rock. To be honest, I have named a few over the years ... I don't know, I just got an intuition for it.”

The increase of hellbenders in the wild is a start. But some of the fundamental challenges facing them still haven’t been addressed. Briggler says sedimentation caused by runoff from plows and other human activity is probably one part of it. Chemical pollutants may also be a factor. Invasive species like largemouth bass and crayfish that are moved around in bait buckets could also impact hellbender numbers. The problem is, these human-influenced threats are all intertwined.

Given these unknowns, the captive hellbender breeding program is more of a stop-gap: It buys the population time. But if the program ended, then presumably the hellbenders would be back on their path to extinction.

In this way, the hellbender's plight is similar to that of the black-footed ferret. Once thought to be nearly extinct, today these distant relatives of domestic ferrets thrive in captive populations raised by the Smithsonian Conservation Biology Institute. They breed in the wild, but eventually the plague returns and the wild-born ferrets succumb to the disease. Inbreeding caused by the severe population bottleneck is also causing genetic defects. If all spending on the black-footed ferret breeding program stopped for 20 years, they would probably become extinct.

Wild hellbenders typically have longer lifespans than black-footed ferrets do. The ferrets typically live three or four years in the wild, while hellbenders can make it into their early 30s. This longevity might make the Missouri breeding and stocking program more durable. Both Ozark and Eastern hellbenders also benefit from intervention that started much more promptly than for the black-footed ferrets. They have genetic diversity in their captive populations that any scientist breeding black-footed ferrets would probably trade a pinkie finger for.

“If you had asked me 10 years ago, I would have said there is a very high likelihood that they will be gone from this state,” Briggler says. “We are buying time and we are buying generations now. These animals can live 25 to 30 years of age. So what we are putting out there gets us 50 years maybe.”

Fifty years of security while scientists figure out how to stem the challenges that face wild-born hellbenders? That's a pretty good deal. To get there, the zoo had to make a big commitment, allocating several full-time staff to caring for the captive amphibians despite the fact that visitors weren’t as charmed by them as zebras or lions.

“It's quite a dedication on the institution's part to put that many people on one species,” Ettling says. “This is probably one of the most worthwhile things I have ever been a part of.”

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