The crayfish towers in my backyard grow faster and higher than the crabgrass, cress, and dandelions do. (I also have some actual grass in my yard but that’s hardly worth mentioning). Each spring, the Burrowing Crayfish (aka Devil Crayfish) pile up dozens of lofty mud turrets. Some, reaching 8 inches in height, cast long dark shadows over the evening lawn which rival those cast by the local mole hills.
The first diggings literally pop up overnight and gain stature over the course of a week or so. They tunnel deep into wet substrate and deposit the excavated soil/mud around one of the opening at the surface. Other entrances are left un-turreted and open flush with the surface. Eventually they complete their work and plug the tower entrances – apparently coming and going via their “naked” entrances.
They are allowed to build their noble chimneys without obstruction because my yard is very wet and the water table is only a foot or so below level surface. A spring stroll across the yard is like walking on a sponge. I don’t get a chance to start mowing until well after the “normal” season for such activity has commenced (at least according to my neighbors who start mowing as soon as the snow is less than 1 inch in depth). In other words, I don’t get an opportunity to knock these towers down – not that I want to – until well into May.
Burrowing Crayfish work and feed under the cover of night so their new construction efforts aren’t revealed until the rising sun of morning. These creatures, although very common, are rarely seen. Last week I took it upon myself to catch one of these clawed arthropods “in the act” and capture it on film…er, digital bits of imagery.
It is assumed that the chimneys are basically the result of excavation and don’t really serve a purpose. In other words, when the digging is done they are normally allowed to collapse on their own. But, it does appear that there is some instinctive need for these turrets early in the season. In other words -again – when they are done they are not really done and will be repaired at least until late spring.
My daughter’s dog accidentally knocked over one of the completed (plugged) towers a while ago. Her antics (the dog’s, not the daughter’s) completely exposed the burrow at ground level. The crayfish re-built much of the turret overnight. The fresh work was apparent as a ring of dark moist soil around the hole. So, I knocked another one of the finished chimneys over and planned on a nocturnal visit to watch the show.
Under the dim glow of a warm quarter moon I snuck across the squishy lawn using my tiny, but intense, Yoda keychain flashlight to illuminate the way. Sure enough, the little Devil was already at work as evidenced by glistening mud pellets piled up on one side. I waited patiently and was able to capture the beast as it returned multiple times with new material and tutored me in the art of chimney building.
The crayfish first appeared at the entrance as a very wet blob of grayish clay. Paired pincers, poking out from the blob, were the only indication that a creature was the impelling force behind the mud ball. In the manner of a bulldozer, the crayfish forced the material up and over the edge. The large pincers (called Chela, if you are a crossword person) are used to contain the sides of the blob while the first pair of legs apparently serve to take up the rear. The whole is retained by the creature’s “face” – leaving the turreted eyes free to search for danger. A few probing pats with the claws secured the mud into position.
Each surface visit was punctuated by an absence of a few minutes as the crayfish descended to the depths to excavate some more material. It was sensitive to my presence and any movement on my part would send it back down for a few seconds, although the camera flash didn’t seem to register any reaction.
On the following morning, I could see that the burrowing beast had completed a small wall around the burrow entrance. Based on what I saw, it would have completed this task within a few hours. I’m assuming the rest of the night was spent feeding and flushing the camera-flash stars out of his eyes. The chimney was sealed shut a couple of nights later. I’ll let this crayfish construction stand for a week or two more until I am able to fire up the mower.