Chimneys in the Grass

 Last week's cleanup, part of the South District Neighborhood Association's Team Up to Clean Up event, was a great success. More than a dozen neighborhood residents and allies came out on a gorgeous sunny morning to fill bags with trash that blew in or flowed into the planted cells lining the trail from the surrounding streets. 

As I was making a last pass along the bottom of the cell just north of the Birds in Flight sculpture, I spotted a much more modest sculpture on the ground. It looked like a rounded urn constructed from hard balls of mud or clay, maybe eight inches tall with a wide opening at the top. I poked it, felt its material was solid and dry, and then hurried off to deposit my bag of trash with the others. As I hurried, I passed a second little urn, also on the ground, also composed of what looked like little mud balls. 

Later in the day, I went searching for the origin of the curious urns. The sheer scale of the construction seemed to rule out any ground-nesting bees or other insects; each of those mud balls would be larger than most insects around these parts and unwieldy to impossible for them to maneuver. A little googling and image searching later, I stumbled across a photo that resembled my urn: it was a a crawfish chimney!

Ah, my sheltered life. I know crawfish (or crayfish, or crawdads). I've seen them once or twice scuttling across the flooded trail down at the Snail Crossing by the Sycamore Apartments. I've admired their sweet pincers and the elegant flared tail. I've marveled at their bright red corpses being gleefully devoured at cajun festivals, or being torn apart on cooking shows. But if I had ever noticed their chimneys before, I never knew the architect behind them.

The crawfish responsible for the chimneys burrow and live underground; the chimneys are the result of the crawfish's excavations, as they carry dirt or mud out of the burrow and place it at the surface opening. But aren't crawfish aquatic? What were these chimneys doing in the middle of the dry planted cells of the Greenway (which, to be fair, can be submerged for days at a time after a rain, but just as often are crisp and dry in the springtime sun)?

To being with...not all crawfish are entirely aquatic! These burrowers, the builders, can live some distance from creeks or other water bodies. They need water to breathe and survive, though, so they will burrow underground until they reach the water table--sometimes several feet. They can leave their burrows for scavenge for food: as detritivores, they will eat just about anything they come across, live or dead, fresh or decomposing. 

These crustaceans, rarely seen from the trail, play an important role in the ecosystem, not only as a clean-up crew for organic material but also as builders of burrows that can be repurposed by other species as a home or refuge: snakes, frogs, insects, and others may take advantage of the work done by crawfish, much the same way that woodpeckers excavate cavities in trees that can later be used by other birds and animals that cannot excavate their own nests. 

Who would imagine, as we cleaned up our human detritus, the unseen crawfish lurking deep in their burrows perform a similar function to keep the Greenway working smoothly?