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Salamander populations are plunging. Zoo scientists in labs and in the wild want to know why.
By Lindsay Renick Mayer
It takes at least five people to catch North America’s largest salamander—the hellbender. Two lift the large rock sheltering the amphibian. Two hold nets on either side of the rock. And one reaches through the murky water with bare hands to scoop the animal up before it darts away.
“You just feel this good squishiness and there’s nothing else like that in the world,” says Kim Terrell, a wildlife physiologist for the Zoo’s Smithsonian Conservation Biology Institute (SCBI). “They are insanely hard to hold onto. They feel like they’ve been dipped in Crisco, and they’re super strong and really fast swimmers. Sometimes at night, I’ll go to sleep, and I’ll just dream about the squish. It’s so good.” Terrell is leading the Zoo’s efforts to study the effects of climate change on the hellbender, which is classified as near threatened. The third largest salamander in the world, it can grow up to 2.5 feet long and weigh up to 4.5 pounds. It is native to Appalachia.
Terrell’s fieldwork is complemented by the research that she’s conducting in the Zoo’s new salamander lab, which doubles as an exhibit. Her study is one of half a dozen salamander-related projects at the Zoo, reflecting a growing focus on conserving one of the most diverse and rapidly disappearing classes of animals on the planet.
Old Dream, New Lab
Over the next hundred years, Appalachia is expected to see an overall temperature increase between 3 and 11 degrees Fahrenheit as the result of climate change. This could be bad news for animals that live in cold, fast-flowing water. The problem is bigger than just hellbenders, though. NatureServe, a nonprofit conservation group that classifies species based on threats, estimates that at least eight species of Appalachian salamanders are at high risk of extinction.
Against that backdrop, Terrell will spend the next two years collaborating with state biologists, academic institutions, and other zoos to determine just how damaging the effects of climate change could be on hellbenders so that conservationists can determine the best methods for mitigating those threats. To do so, she has designed an experiment that will look at how different kinds of temperature change affect hellbenders’ ability to breathe and to fight off disease.
The first part of the work with the Zoo’s 18 young eastern hellbenders (a subspecies) will focus on short-term temperature fluctuations like those the animals would experience over a week—or even in a few hours—in the wild. The second and longer-term part of the study will look at both seasonal changes alone and seasonal changes plus four degrees Fahrenheit to simulate a conservative estimate of predicted climate change.
Working with animal care staff and Suzan Murray, the Zoo’s head veterinarian, Terrell will use blood samples to examine the animals’ white blood cells, which can indicate their level of stress and susceptibility to disease. She’ll also measure their oxygen intake. Like all amphibians, hellbenders breathe through their skin. The wrinkles in their skin give them more surface area to take in oxygen from the water they live in. The warmer water is, the less oxygen it contains. Because oxygen drives metabolism and energy production, it’s possible that global warming could stunt salamanders’ growth.
All of this work is now on exhibit in a new salamander lab in the Zoo’s Reptile Discovery Center (RDC), highlighting the collaborative efforts between the Zoo’s animal care team and scientists. The salamander lab was the long-time vision of RDC curator Jim Murphy, who recognized in the late 1980s that rapid declines in amphibian populations indicated that something ominous was going on. Today visitors to the Zoo have a chance not only to see the hellbenders, but to interact with Terrell, other scientists, and the animal care team as they go about their work.
That connection between visitors and scientists is crucial, says senior curator Ed Bronikowski, who helped facilitate construction of the lab: “The single thing that distinguishes the National Zoo from all other zoos is our Smithsonian science. That is who we are; that is what we do.”
Giants Among Us
Hellbenders—or “snot otters” as they are called in some parts of Appalachia— belong to the Cryptobranchidae, a family of amphibians that live in brooks and streams. The group includes the largest amphibians in the world: Chinese and Japanese giant salamanders. They grow up to six feet in length.
Although cryptobranchids have survived three mass extinctions in Earth’s history, modern-day threats are causing their numbers to drop precipitously in both Asia and North America. Scientists fear that the salamanders may not survive an unprecedented array of threats, including climate change, habitat loss, pollution, disease, and the introduction of new predators. This was, in part, why the Zoo established, in 2010, the first breeding center for Japanese giant salamanders outside Japan.
Four Japanese giant salamanders live in the breeding center in RDC, while one is on exhibit on Asia Trail. Animal care staff attempted unsuccessfully to breed the animals this year, but Bronikowski says they are likely still too young. The staff will try again this August when the breeding season starts up again.
In the meantime, the Zoo’s Japanese giant salamanders are helping researchers understand one of the biggest threats to amphibians—a fungal disease called chytrid. Nearly a third of the world’s more than 6,000 amphibian species are in danger of extinction, due in large part to chytrid. This could result in the worst extinction event since the time of the dinosaurs.
When the five Japanese giant salamanders came to the Zoo in 2009, they tested positive for chytrid. Although chytrid has been deadly to frogs, it isn’t lethal for Japanese giant salamanders. It appears to be akin to athlete’s foot in humans. Murray was able to cure four of the salamanders of their chytrid. (She left the fungus on the fifth salamander so that scientists still have a sample for research.)
Cracking the Chytrid Code
Zoo geneticists are trying to discover why chytrid kills frogs but not Japanese giant salamanders. Researchers already know that the chytrid found on Japanese giant salamanders is slightly different from that found on frogs. They hope to begin to understand the difference by comparing the DNA sequences of various forms of the fungus. This research may also help scientists understand whether chytrid is a threat to hellbenders.
SCBI scientists have detected chytrid on amphibians in Appalachia, but the fungus is less prevalent than in the neotropics. The Zoo is working with chytrid specialist Karen Lips of the University of Maryland and National Museum of Natural History curator Roy McDiarmid to determine whether chytrid has already swept through the region, leaving animals that have developed a resistance to the fungus as a result.
To determine if this is the case, the Zoo and its collaborators are looking back in time. They are studying nearly a thousand samples, collected in Appalachia during the 1950s through the 1980s. Scientists are examining the samples for chytrid DNA. “If chytrid did knock down Appalachian salamander species, we should expect to see no trace of chytrid up to a certain point and then a blast where there’s very high prevalence of infection and then a drop as the salamanders developed resistance or chytrid evolved into something less deadly,” says Rob Fleischer, head of SCBI’s Center for Conservation and Evolutionary Genetics. “When this work is complete, we hope to have a much better handle on what caused this massive decline.”
Mysteries of the Shenandoah
Hellbenders are not the only Appalachian salamanders on the Zoo’s agenda. Since 2007, Jennifer Sevin, a biodiversity conservation specialist for SCBI, has worked with state, federal, and academic institutions to monitor redback salamanders and endangered Shenandoah salamanders at more than 124 monitoring sites in Shenandoah National Park.
Sevin is looking at competition and hybridization between the two species and examining the characteristics of their sometimes overlapping habitats. She and her collaborators are exploring whether temperature and relative humidity help determine the very specific areas in which the animals live.
“The biggest mystery is what the salamanders are doing underground,” Sevin says. “Right now we don’t have a good explanation of why the Shenandoah salamander lives where it does. I’m hypothesizing that there’s something underground keeping it in those spots, but that’s probably going to be an ongoing mystery for a while.”
Sevin’s work also has a Zoo component. Last year, she and her U.S. Geological Survey collaborators looked at how redback and “leadback” salamanders in the Zoo’s climate chambers responded to temperature and humidity changes. (A “leadback” is a redback without the distinctive red stripe.) The next step in the research is to do the same experiment with Shenandoah salamanders.
The researchers hope their work has a practical impact. “Most people would assume that because it’s a national park, the salamanders are automatically protected,” Sevin says. “But there are activities that go on in a park, and management agencies have to make decisions all the time. I hope our research is used to help them make decisions to better protect these species.”
SCBI’s focus on Shenandoah salamanders and hellbenders is strategic, according to Brian Gratwicke, an amphibian conservation biologist. “Shenandoah salamanders are a natural fit because they’re a mountaintop endemic species that’s federally listed and only found in three mountaintops in the Shenandoah National Park,” he says. “Hellbenders really complement that approach because they’re restricted to larger mountain rivers. They represent the opposite end of the spectrum for Appalachian species, but we believe they are also affected by climate change.”
Cutting edge though it is, salamander research also brings the Zoo back to its roots: the conservation of North American wildlife. With Appalachia as the world’s hot spot for salamanders (see sidebar), Gratwicke says, “we need to learn all we can to protect them as a national treasure.”
-- LINDSAY RENICK MAYER is a public affairs specialist for the Smithsonian's National Zoo.