Sounds in the Darkness

In their ever-shifting world of opportunity and vulnerability, Chicago-region frogs have to seize the day.

by M.G. Bertulfo

I’ve always enjoyed the sounds of darkness,” says Espie Nelson. For years, she and husband Don Nelson monitored frogs in Lockport for the Habitat Project’s Calling Frog Survey. “You don’t start monitoring until half an hour after sunset. We’d go out early, watch the sun go down, and see the stars come out... You hear the sounds of the prairie and wilderness.” Don describes that moment of hushed anticipation: “You hear the transition from the birds singing to the frogs starting to sing.”

And so it begins, each spring, in thousands of preserves. Across the region, the male frogs gather. They perch on tree branches, stand upon mudflats, sandy shores, and matted algae. Their calls issue from their tiny bodies, vocal sacs ballooning like giant, inflatable amplifiers in a full-body bid to claim territory and call for mates.

But this ancient amphibian rite may be vulnerable to a coming plague. In the last 20 years, according to the Global Amphibian Assessment, nearly 168 amphibian species have gone extinct in the wild. Today, over 40 percent of the planet’s 6,300 amphibian species are in danger of extinction. To raise public awareness, the Association of Zoos and Aquariums and many global partners declared 2008 “The Year of the Frog.”

A deadly fungus has recently been shown as a central cause of the die-off. “A frog’s skin becomes completely filled with fungal bodies,” explains Southern Illinois University zoology professor Karen Lips, a key researcher who helped identify the chytrid fungus as a leading factor. “The poor frog apparently isn’t able to get enough water or oxygen across the skin into its body.”

Researchers are concerned that this seemingly distant problem could become ours as well. Though our high summer temperatures may be keeping it in check, the chytrid fungus was first recorded in Illinois in 1999. Lips and SIU zoology doctoral student Brooke Talley are researching its distribution and prevalence in different species and habitats.

And though the fungus has not yet been found in Chicago Wilderness, researchers are only now beginning to swab frogs here. They expect to find the fungus in new places. According to the World Conservation Union Red List, the 13 frog species of our region are holding steady. But is the fungus our wake-up call? Is it time to stop taking our frogs for granted?

Frogs of Chicago Wilderness

“Frogs returned to the Chicago area around 12,000 years ago, after the last glacier melted,” says Ellin Beltz, author of Frogs: Inside their Remarkable World. “Giant lakes and huge floods helped sculpt the features left behind by the glacier.” The glaciers left us “a highly diverse series of environments, including prairie, oak savanna, sand areas, eastern forest.”

Over thousands of years, our frog and toad species have adapted to this unique terrain. In the span of a lifetime, each species can be found thriving in two or three different wetland niches. Eastern gray treefrogs, Hyla versicolor, and spring peepers, Pseudacris crucifer — to take just two Chicago-region frogs — spend their adult lives in savannas and dense woodlands. Then they breed in swamps, marshes, and ponds. Fifty feet above the ground on oak limbs, the treefrogs gather, buzz, and trill. When night falls, their toe-pads grip the bark and they slowly descend the tree trunks to ephemeral pools, dark mirrors at the feet of the trees. From briars and buttonbushes along the water’s edge, spring peepers emit a series of short, high-pitched peeps.

Few people experience this alternate world of the evening wetland, with its ancient amphibian rites, in the way that frog monitors do. Three times a year, March through June, about 100 volunteers gather data on frog distribution in the Chicago region. Equipped with bug spray, flashlights, and data sheets, they enter the wetlands. From a training workshop, they’ve learned the 13 local species’ calls. At listening points along their set monitoring route, they wait patiently for chorusing to begin. Then they write down the weather conditions, which species they hear, and the strength of each chorus.

The monitors’ camaraderie and sense of humor is effusive. They laugh at how, in their own eagerness as novices, they occasionally mistook birdcalls for frogs. Over the years, they say, the identification gets easier.

Given frogs’ amazing ability to metamorphose, smell things on land and in water, catch insects with a flick of their sticky tongues, breathe through their skin, and see in many directions at once, they have endeared themselves to local monitors, herpetologists, and conservationists. “We care about them and we love them,” says Karen Glennemeier, science director for Audubon–Chicago Region. “They’re very charismatic in their own way.”

Judy Boehmer’s childhood adventures in nature inspired her to become a Kane County frog monitor. “I was in the woods with my grandpa. We were hunting mushrooms. I remember being in awe of the woods. Then, we came upon a pond. I saw these tiny frogs. They may have been little treefrogs. I remember seeing them everywhere and being so awestruck by it.” Just outside of suburban Elgin, Boehmer now monitors a series of low-lying ponds along a creek where she once again encounters gray treefrogs.

Diana Krug, a south Cook County monitor, lauds the importance of frogs “because they maintain a place in the food chain where they’re in the middle.” Diving beetles, fish, snakes, herons, and raccoons prey on eastern gray treefrogs, and spring peepers. Each frog has its own unique way of coping with predators. Spring peepers are strong jumpers. Eastern gray treefrogs secrete toxins that cause a burning sensation. Some male treefrogs even play dead when captured.

Frogs prey upon smaller animals, too. Eastern gray treefrogs eat wood roaches, earthworms, beetles, camel crickets, and flies. Spring peepers eat spiders, mites, ants, and insects that are attracted to flowers.

Krug admires the tenacity of these “beautiful little creatures.” Eastern gray treefrogs expend much of their energy “trying to get a mate, clinging to a limb, and calling…They’re going to get the best mate by calling the loudest and the longest.”

Nicky Strahl, a Lake County monitor, revels in the noisy choruses made by spring peepers, the males of which call in duets and trios to attract mates. “We’d go out to the first site and it would overwhelm you. You’d be surrounded by sleighbells — that’s what they sounded like.”

Diane Huebner, a north Cook County monitor, appreciates how local frogs embody the philosophy of carpe diem. When the water is there and the temperature is right, frogs seize the opportunity to recreate life. “Frogs are quick breeders,” she says. “They go out, they sing, they mate, they lay eggs. Then the eggs hatch and the tadpoles only have so much time to live in the water before the ephemeral ponds will dry up.” Ephemeral ponds flood in the springtime and dry up in the summer, keeping tadpole-eating fish out.

Frogs’ “boom and bust” lifestyle—breeding profusely in good conditions or not at all in bad — makes them sensitive to changes in the environment, a trend borne out by monitors’ data. In healthy wetlands in good years, monitors find these frogs calling, breeding, and thriving. At the other end of the spectrum, they see the effects of an often harsh, shifting environment. They express strong concern, in particular, for the plight of northern cricket frogs. Cricket frogs are smaller than many insects, measuring only three centimeters long. A triangle marks their heads and webs extend between the toes on their hind feet. In Chicago-area prairies and savannas, they once bred widely in the sunny shallows of lakes, ponds, marshes, and streams. During the nineteenth century, these leggy frogs were abundant in all parts of Illinois. Their range extended across the eastern half of the United States, from Kansas to New Jersey. But in the 1970s, they mysteriously disappeared from the upper Midwest.

“During one of the earlier droughts when all the ponds went dry, they seemed to have disappeared from the Lockport area like they did from most other places,” recalls Don Nelson.

“We want to find out why it left and if there are ways to help it return,” says Karen Glennemeier, science director for Audubon–Chicago Region, “not because it’s a species of global concern, but because it’s part of our regional biodiversity.”

Since cricket frogs live an average of eight months and don’t breed until they’re a full year old, many don’t live to mate, so it takes populations a long time to rebound from losses, says U.S. Fish and Wildlife Service herpetologist Mike Redmer.

Why did cricket frogs decline in Chicago? “There are a bunch of competing theories as to why it happened,” says Ken Mierzwa, a restoration consultant in Chicago for over 20 years. These include agricultural pesticides, a parasite problem, ultraviolet-B radiation killing floating egg masses, an unusually harsh winter, and extreme weather.

But whatever factor pushes a species over the edge, several others can weaken frogs’ resistance. The biggest challenge faced by local amphibians, Mierzwa believes, is fragmentation of wetlands. Normally, when cricket frogs are killed by drought or other causes, the survivors recover by migrating along streams to alternative ponds and marshes. But humans have changed the natural water flows by building channels, canals, and drainage ditches. As Robert C. Lacy, conservation biologist for the Chicago Zoological Society notes, “We might be keeping our feet dry at the expense of frogs being able to breed.”

“Many wetlands have been drained in states like Illinois and Indiana to create farmland and housing,” notes Robert Brodman, a St. Joseph’s College biology professor. “There has been a large loss of amphibians directly due to their habitat being destroyed. The habitats that are left are sometimes fragmented and isolated.”

Notoriously thin-skinned, frogs are also extremely sensitive to pollutants, leaving frog advocates to troubleshoot ways to keep salt- and oil-laden road runoff out of wetlands.

The good news is that frogs respond well when they have choices and continuous access to healthy savanna, prairie, and wetland habitats. In McHenry County, Mierzwa “witnessed explosive growth in frog numbers in the cool and wet summer of 1993. For the most part, they’re pretty resilient critters if we give them half a chance. After all, they’ve survived for many millions of years.” Since 1999, Brodman has noted frog populations in northern Indiana and Illinois “getting bigger and spreading…they seem to be rebounding.” With access to streams, frogs can migrate easily from pond to pond.

This decade has witnessed the hopeful return of cricket frogs to Kendall and Kane Counties, where monitors confirmed their discovery in 2000. And, says Don Nelson, “Even though they’re a rare frog in the Chicago area, they’re relatively common in Lockport now. They sing a lot during the day.”

Pockets of cricket frogs survived in Wisconsin, Michigan, Iowa, and in Illinois along the lower Des Plaines River and the Midewin area, says Redmer. “There’s still cause for concern with the cricket frog. It’s clearly not as common in the Chicago area as it was 30 years ago. But,” he adds, “I’m a little optimistic. If there’s habitat they can occupy, they’re going to do it.”

Resilient creatures like gray treefrogs, spring peepers, and cricket frogs have survived the planet’s changes for roughly 200 million years. Now, more than at any other time in history, it is important to celebrate and protect the amphibians living in Chicago Wilderness. Against the background of a mass global amphibian die-off, monitors in Chicago have literally been counting their blessings with each trill, peep, and click in the night. With any luck, their work will help us protect these wondrous choruses as they sing out their lust for life.

Become a frog monitor for The Habitat Project.

Related articles:

Western Chorus Frog: Audible but Seldom Seen, CW Spring 1999

Gray Treefrog: Master of Camouflage, CW Fall 2002