File:Crayfish Chimneys on Seedskadee National Wildlife Refuge (22539466001).jpg

In some locations they are called mudbugs or yabbies. In Wyoming, most of us call them crayfish, crawfish, or crawdads. These are all names for freshwater crustaceans resembling mini lobsters.

This photo shows several crayfish chimneys. They are those "smokestack" looking things that appear as wetlands begin to dry out. Everytime you see one, there is a crayfish living in a burrow beneath the chimney. Their tunnels may extend down into the earth 3 ft or more, sometimes being a single burrow going straight down, but more often being a main tunnel with a couple of side tunnels, each with an enlarged "room" at the end. They are normally full of water, filled by groundwater.

Crayfish use their legs and mouth parts to dig up mud and make it into a little ball of mud. Each ball is taken to the surface and placed around the entrance hole. Each new ball is stacked on another. This continues, much like a brick layer putting bricks on one layer at a time. The crayfish makes the chimney out of many, many balls of mud.

Crayfish begin to dig burrows as water levels recede inorder to be able to submerge beneath the water table. As it does so, it has to do something with the mud. If it takes the mud outside the burrow and crosses the ground to dispose of it, the crayfish will be vulnerable to predators. To avoid that, they build a chimney, thus never leaving the entrance of the burrow.

What happens to burrowed crayfish during droughts? One of their first responses is to plug their burrows with mud. As the water table drops, the animal moves further down (this is the same response they have to cold weather - they move down below the frost line). Crayfish in the River do not show this same response, as their is no need to build a tunnel unless the River were to completely dry out or freeze solid to the bottom.