At the USGS, Amphibians are Out of Sight but Top of Mind
It’s a warm, humid evening in a swampy wetland somewhere in the extreme southeastern United States. A soft breeze causes the grasses and willows to sigh and the high-pitched whining of insects begins.
Nearby, a guttural croak adds to the ethereal springtime symphony. Soon, more guttural croaks join in. The croaks build in a slow crescendo as the night progresses until there are too many to count.
The source of the croaking is pig frogs—so named because their call sounds like the snort of a pig. Despite being fairly abundant and clearly present, it’s likely you’ll hear thousands of these amphibians before you ever see one.
Pig frogs are cryptic, a term scientists give animals that rely on camouflage and sneakiness for survival. That’s true of most amphibians, and some don’t make any noises that people can hear, so you could go your entire life without knowing they even exist. Consider the contrast with more visible wildlife, such as birds.
“Birds are flamboyant show-offs,” lamented Evan Grant, U.S. Geological Survey research wildlife biologist and lead scientist for the northeast region of the USGS’s Amphibian Research and Monitoring Initiative (ARMI). “They are easy to spot and watch flitting around. But to fully experience the amphibians around you, like you can with birds, you have to go where they are. Get on their level.”
In contrast, amphibians—by nature—live in habitats that take a little extra planning and courage for people to enter. Waders, a headlamp, a big net, a willingness to wade into deep and cold water … Plus, amphibians are good at hiding from predators that primarily use their eyes to hunt, like people.
For Grant, out of sight isn’t out of mind.
People prize places with high biodiversity, places that are rich with living things. They are often the same places people are drawn for their obvious benefits, which tend to include abundance of food and fertile soil. Yet, there are hidden aspects of biodiversity that often go unnoticed.
“For people who don’t spend most of their time thinking about the hidden living things, it’s easy to think what you see is what you get,” Grant said. “It’s harder to appreciate organisms that remain hidden. But that desolate-seeming creek or pond nearby may, in fact, be a vibrant and diverse ecosystem that is bursting with life.”
Since all amphibians are at least somewhat aquatic and they are sensitive to changes in their habitats, their status can also provide important feedback on the health of the environment, like if a body of water has become polluted.
Unfortunately, amphibians are signaling there’s a problem.
Twenty-five years ago, amphibian biologists announced an alarming trend in amphibian populations around the world. Many species are declining.
Grant and other USGS amphibian biologists are leading the way in monitoring amphibians and understanding causes of their declines.
Finding what was harming amphibians–and ways to conserve–them became a priority. In 2000, the Department of the Interior was directed by the U.S. Congress to keep track of amphibians on public lands and determine what was contributing to their decline.
In response, the USGS established ARMI to organize the scientific expertise within the agency to monitor amphibian populations and research the cause of their declines.
Today, the USGS partners with other agencies to fulfill ARMI’s goal to “provide essential scientific information to managers to help arrest or reverse amphibian population declines.”
In the recently released “State of Amphibians in the United States,” ARMI summarizes what scientists know about the issue of amphibian population declines so far. In short, there are many factors contributing to the declines with habitat loss, introduced species, and disease at the top of the list.
But there’s also an elephant-sized giant salamander in the room—climate change.
Amphibians are especially vulnerable to the effects of climate change, which can have direct effects on things like water availability and indirect effects by making problems like disease and invasive species worse.
Extreme events linked to climate change that impact amphibian aquatic habitat like drought and coastal flooding are causing declines in amphibian populations.
While the direct and indirect impacts of changing climate on amphibians are still being teased apart, it is clear that rapidly changing environmental conditions, whether linked to climate change or not, are taking their toll on amphibian populations.
Although they’ve been around for millions of years, today, amphibians are the most endangered class of vertebrates worldwide.
Dedicated scientists and amphibian enthusiasts are sounding the alarm. But amphibians’ cryptic nature, which helps them avoid being eaten or sneak up on prey, also makes it hard to find and hard to study them. Unfortunately, a lack of information about a species can lead to it being overlooked in conservation efforts.
The USGS recently supported a study that used a very large dataset to determine which frog and toad species are most vulnerable to climate change, and assess whether their vulnerability was correlated with conservation status. The surprise result: it turned out there was no correlation between a species’ vulnerability and its status leaving many rare, isolated species unprotected.
This mismatch in vulnerability and conservation status underscores the critical need for amphibian monitoring efforts like those undertaken by ARMI. Successful management of species relies on having good information. Lessons from long-term monitoring programs can even benefit new programs.
Beyond monitoring, USGS scientists are directly involved in amphibian conservation efforts.
For example, the USGS and partners are determining ways to successfully reintroduce amphibians to areas where they had previously disappeared, like the mountain yellow-legged frog in California and Chiricahua leopard frog in Arizona and New Mexico.
Scientists at the USGS are also working closely with natural resources managers to help in the management of amphibian species. The USGS has expertise in leading formal decision-making processes to determine the best course of action to conserve imperiled species, which combine the goals of land managers, scientific expertise and computer modeling to identify and prioritize gaps in knowledge for future research.
In a recent example, Grant joined with fellow ARMI Biologist Molly Bletz to lead one of these processes to help inform the management of the Sacramento mountain salamander. Grant brings his expertise leading similar workshops for the Shenandoah salamander to the effort.
“Working with state and federal agencies and Tribes to help conserve another imperiled salamander species is very fulfilling,” said Grant. “These are hard issues to manage, but I’m inspired by the commitment of the people working on them.”
Whether you find them endearing or revolting, amphibians are important parts of the ecosystems they belong to. They are both predators and prey, and their unique place in the food web means that they provide us with clues to the overall health of an ecosystem.
With the dedication of scientists like Evan Grant, there is hope that amphibians will remain hidden biodiversity instead of biodiversity that’s been lost altogether.
Curious about the amphibians in your neck of the woods?
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