Frogs and toads fill our summers with sound, but where do they go in winter?
Editor's note: Karen Glennemeier, a research biologist on Shedd Aquarium's freshwater research team, has decades of experience in amphibian research and habitat restoration. The scientist from Wilmette focuses her studies on amphibians that live in Chicago-area forest preserves.
On calm summer nights in our local woodlands, as water trickles through rocky streams and the moon glistens in the reflection of small ponds, local frogs and toads fill the night's silence with croaks and ribbets - mating calls to one another.
But what happens when the nights turn colder, moving water slows to a freeze and lush greens are covered with fluffy white snow? Where do the amphibians disappear to?
In the Chicago area, 13 species of frogs and toads live in our woods, prairies, savannas and wetlands. The American toad might be one of the most recognizable, but it is joined by other important species like the western chorus frog, the spring peeper and the wood frog. Their size and color make it easy for them to hide from us humans, even when they're hopping all around us in the woods.
In the spring and summer, these hidden hoppers flock to areas with moisture, like shallow ponds or small streams. They eat pesky mosquitoes, as well as other insects and plants, and this helps to keep our ecosystems in balance. They also serve as food for birds, foxes and other predators, so they're an important part of the food web.
But the reason you've likely never seen a frog or toad hopping through the snow in January is because they're safely nestled in warmer areas - most often, right underneath your feet!
Unlike humans, frogs and toads are coldblooded. This means they adapt to the weather around them. For some, this means freezing their bodies almost entirely solid until they thaw out in the spring; such is the case for wood frogs and spring peepers. For those that are better at burrowing into the ground, they dig deep into the earth's soil and hibernate, safely below the frost line.
Similar to bears, which tend to plump up before hibernation, frogs and toads also load up on food before sleeping away the winter. While Chicago winters might seem too long and extreme for frogs and toads, there are some species that can survive the climate in the Arctic Circle!
In the middle of January, amphibian species are far out of sight. But thanks to a new research project that Shedd Aquarium launched last year, it's likely that many are burrowed right below our feet.
Last spring and summer, our team monitored about a dozen ponds for amphibians and counted thousands of tadpoles, as well as several species of frogs, toads and salamanders. These dozen ponds are suffering from a condition that faces many of our woodland ponds - they are choked with invasive brush and surrounded by bare ground that might not be providing amphibians with good habitat.
Staff and volunteers with Shedd's Great Lakes Action Days program, alongside land managers and volunteer stewards with the Forest Preserves of Cook County, spend many cozy winter days outdoors, removing this invasive brush in the hopes of restoring health to these ponds. We also spread the seeds of dozens of local wildflowers and grasses from nearby preserves, adding plant life back to the bare ground.
Our end goal is to understand how frogs and toads are responding to efforts that restore their habitats. Do they notice all of our hard work? Are they laying more eggs? Are more tadpoles surviving in these ponds once we remove invasive plants?
We're spending the winter restoring health to half of these dozen ponds. Next spring, we'll revisit all dozen ponds and see if more amphibians are breeding in the restored ponds compared to the others.
While the cold weather extends invitations to enjoy a good book or warm company by the fire, you can help restore the habitats of these important local amphibians with us! Year round, the Forest Preserve Districts of Cook, DuPage, Kane, McHenry, Will and Lake County all offer opportunities to help restore wooded areas to their former native glory. Our team at Shedd hosts these important volunteer restoration days in Northbrook and LaGrange in Cook County. You can join us by visiting www.sheddaquarium.org/GLAD.
As you wander outside this winter, be sure to give the ground a good foot-tap to say "hello!" And, join us in looking forward to the spring thaw when ribbets and croaks will reappear.