As the name implies, such a place is a now-you-see-it-now-you-don’t phenomenon. It’s little more than a poorly drained depression in the land, and the spring rain pours in as winter recedes. Life awakens from dormant forms buried in the ground: fairy shrimp, daphnia, copepods. When summer heat arrives, slowly, pools like this wither and dry.
In fact, it’s likely that a visitor would mistake the ephemeral pond outside the Wehr Nature Center for a muddy puddle.
On a cool day in mid-March, spring has not yet mounted its verdant, vibrant push. Yet this dark pool is building momentum, waking spores and larvae and gathering eggs. A clamor of frog calls rises. “They sound like cackling old men in the woods,” Julia Robson says, identifying them as wood frogs before asking, “Ready for some fun?” Clad in thigh-length waders and a quilted dark Milwaukee County Parks sweatshirt, Robson picks her way through the underbrush to the sodden edge.
These pools serve as essential incubators for the tiny critters that call them home. In Wisconsin, they are as crucial to some amphibians and their wetland companions as coral reefs are to fish in the sea – a place to spawn, a place to get big enough to brave the wider world. Their importance to the ecosystem explains why a growing crew of scientists, both professionals and citizens, takes to the marshy landscape each spring to catalog and protect what lurks within.
Robson’s title is assistant natural areas coordinator, but her metier is clearly mud. “It’s like every year I have to learn to walk again,” she laughs as her feet feel along the bottom, invisible under the turbid slosh of mud and dead leaves. She’s learned the hard way that it can get suddenly, surprisingly deep: “You’re not a wetland monitor until you fill your waders.”
As she sloshes forward, the two-part harmony of wood and chorus frogs has gone silent. Three mallards skitter across the water. Robson retrieves the first traps — two wire mesh buckets clipped together, with funnel-shaped holes in each end — and not much of interest is recorded.
Another trap, lying against a fallen log, provokes a sharp cry of delight: Robson spots the ferocious larval form of a water tiger, a species of predacious diving water beetle. “They are vicious,” she says. Once she watched a worm struggle for its life as it was torn apart. After a few moments of displaying it on her hand, she anxiously lets it go, wary of the bite. “I let it happen once, just for fun, and it did not feel great.”
Still shriveled in the crease of the trap is what appears to be a wad of leaves, but Robson reaches in and expertly teases out a wood frog. Dark green and gilded, it sits quietly, immobilized on her hand. Once ubiquitous, the species currently survives at only two of Milwaukee County’s more than 140 parks: here, and at Greenfield Park in West Allis.
What’s special here is not just the water, but the surrounding woods. The pond is critical breeding habitat, but is not sufficient. Once the tadpole is ready to lose its tail and leave the water, it can’t survive in grass or pavement. It needs a home.
Robson takes note of a few stumps along the road, signs of the evolving landscape. Trees damaged by the emerald ash borer had threatened the roadway and were removed. The extra wood in the wetland is probably a good thing. But the change in shade will affect local temperature and humidity. “How is that going to affect the amphibians that are using it?” she asks. “That’s not just here. A lot of our canopy is green ash. It’s going to be systemwide.”
As many as 9,000 potential ephemeral ponds were mapped in the eight counties of southeastern Wisconsin between 2004 and 2010. It’s a hopeful number, but nowhere close to as big as it sounds. These are barely pixels, isolated remnants of a fading and disconnected landscape. But they are critical habitat for some amphibians, which the International Union for the Conservation of Nature has called the most threatened vertebrate group. Worldwide, around 40 percent of amphibian species are at risk of extinction.
Money from the Great Lakes Restoration Initiative has allowed Gary Casper of the University of Wisconsin-Milwaukee Field Station to begin canvassing these wetlands in the northern half of Milwaukee County, and he’s had a chance to reflect on their value.
“This is a young system in geologic time,” says Casper. From a planetary perspective, we’ve just barely emerged from the ice. What we see here in Wisconsin is only a couple of thousand years old – mostly common generalist species that don’t have very specific habitat needs. That’s why there are so few things in Wisconsin that are currently considered globally threatened.
“But all conservation is always local,” says Casper. “You really want to look at what’s happening on your landscape, in your neighborhood. When you look at it that way, then things change dramatically, in terms of what species would be of conservation interest.” Ephemeral wetlands are particularly vulnerable because they are often isolated and disconnected from other water bodies, and even the land around them. The land is often mowed or paved right up to their edge; it’s the loss of that connection to upland habitat that’s particularly damaging.
“It’s very clear from our work that when that happens diversity declines drastically. We might just have bullfrogs and toads,” he says. Without nearby habitat, wood frogs, chorus frogs, leopard frogs and salamanders vanish.
Wisconsin does have its curiosities, and Casper and Robson are particularly entranced by a few uncommon species of burrowing crayfish: the prairie crayfish, the devil crayfish and the digger crayfish.
“Very few people know much of anything about this kind of crayfish, which are almost terrestrial,” explains Casper. They dig deep burrows down to the water table. They love ephemeral wetland, whose very nature provides the soft, wet soils in which they thrive.
The prairie crayfish is relatively common in Wisconsin, yet largely unknown because it’s hard to survey. Casper developed a new technique for trapping and verifying their presence. Then, in 2011 in Ozaukee County, he caught a digger crayfish. “It had never been found in Wisconsin,” he says. “They are the rarest crayfish out there.” Poking around museum collections in Madison and Milwaukee didn’t provide much more clarity about their historical range, but continuing surveys have discovered several more populations.
While the parks system has only two employees to study all of the wild nature within its entire system, a grant from the Wisconsin Citizen-based Monitoring Network has allowed Robson to engage a volunteer corps of aspiring naturalists.
Last spring, more than three dozen volunteers logged 625 hours monitoring 20 different wetlands, documenting nine new blue-spotted salamander populations, three new digger crayfish populations and the first spotted salamander recorded in Milwaukee County since 1934.
This kind of documentation allows the parks to make better decisions about how to use their land and resources, but Robson has even more ambitious plans. Once they have a better understanding of these wetlands and their strengths and weaknesses, she hopes they’ll be able to transplant egg masses around in the spring, and bring the wood frog and other species back to a broader range across the county.
Last year, Julie Hahm and a handful of her students monitored the ephemeral pond at Wehr. They were the ones who caught the very rare spotted salamander. Although there is no recent record of breeding, but it was a hopeful sign nonetheless. Also, it was fun.
“They love tromping around in the waders,” says Hahm. “It’s really neat to get them outside more often.”
This year they’ve moved to a new site in Barloga Woods, a few miles from Greendale High School, where Hahm teaches chemistry and environmental science. Walking through the oak and hickory woods toward the wetland, Hahm is excited because on most sampling trips she’s just the chaperone and recording secretary. With no students along, she’s actually going to get to check the traps.
Robson has asked to tag along because the kids believe they have found a digger crayfish. The digger is not an earth-shaking discovery, and yet it speaks to the delightful potential of these soft spots on the landscape to connect people and nature.
“Almost all herpetologists I know started out catching frogs in their neighborhood,” says Casper. A burgeoning body of research links happiness and stress to our connectedness with nature. “The more green space and nature you have around you, the better your health and well-being. How do we have a thriving community with a lot of social interaction but also have people connected to nature?”
Especially here: Barloga Woods backs up to Interstate 94, and the wetland is just a stone’s throw from the highway. There will be no frog chorus here, yet even as the rush-hour river of steel roars past, the water in the wood connects us to a different pace, a different place.
The first trap yields a crayfish, but it’s not much bigger than a pinkie joint. At that size, it’s almost impossible to determine species, but as the tail catches the light Robson gasps. “Oh my God, look at those two straight lines,” she says.
“I’m never very comfortable identifying crayfish that are this young because the patterns can be variable,” she says. But she opens a binder and points to the two darker bands marking the greenish-brown tail of the typical digger crayfish. They are distinctive, and unmistakable even on the tiny creature in her hand. “This really stands out,” she says.
The next trap holds an even bigger surprise: two small fish. Fish suggest this is not actually — or at least not always — an ephemeral pond, but that’s a discussion for another day. The trap also yields a blue-spotted salamander and another crayfish. It’s the first salamander of the day, but it’s overshadowed by Robson’s pure delight. “These are diggers!” she says. “That one is a digger crayfish! Ooooo-woooh!”
The stripes are even clearer, but here she can also see the “pug” face. “The diggers barely have a rostrum — a nose. It’s almost like the face ends,” she explains. “There is no arguing with that.”
She’s flush with a naturalist’s high: In a profession so often filled with news of things lost, something has been found again. And for this moment, only this tiny expedition knows. Robson’s eyes pop wide in excitement and her mouth forms a vivid “O.” She can’t wait to tell Casper.
Working through the last traps, we exit on the other side of the marsh and traverse the muddy fringe. Here we find the burrows, which are mud-crafted domes that look a bit like miniature volcanoes. “Crayfish burrow mania,” says Robson. “Look at all of these!” Peer down, and you can see a piece of the reflected sky: The tunnel reaches groundwater.
There is nothing ephemeral about Robson’s energy. She finds a deer antler, collects it, notes where critters have gnawed at it for the calcium, then replaces it. She stops and pulls at an emerging thread of vegetation on the forest floor. You can see an ID flash across her eyes, or perhaps a question stored for later.
As a farewell she reaches down compulsively and lifts a log. “Just can’t help it sometimes,” she says. “When you see a good log you just have to turn it over.”
Erik Ness is a freelance writer based in Madison.
