Crayfish Mounds

Because crayfish are nocturnal, they typically excavate dirt and create their burrows only at night. They create tunnels that angle in different directions, from straight down to sloping. Complexity is largely tied to the type of burrowing crayfish. Every burrow has a resting chamber, which holds water. The resting chamber is where crayfish sleep and spend much of their time, especially during the day, when inside their burrows. Burrows have a few purposes, including providing a resting place, offering a source of water and serving as a breeding ground. Douglas Smith, author of "Pennak's Freshwater Invertebrates of the United States: Porifera to Crustacea," notes that only one crayfish lives in a burrow at a time except during the breeding season.

Primary-burrowing crayfish spend most of their life in burrows. Rather than seeking out bodies of water, primary burrowers look for damp, soft ground and then set up shop. They begin creating burrows that "West Virginia Wildlife" magazine says can reach almost 6 feet below the surface. And it's typically not a straight shot. The complex burrow system consists of multiple paths that branch off in different directions. The burrows usually connect to the water table but not an open body of water. Some burrows do not connect to the water table and instead rely on surface water runoff. Primary-burrowing crayfish excavate large amounts of dirt that they then build into what the Georgia College website refers to as mounds that resemble dirt chimneys. Primary burrowers generally leave their burrows only if they're in need of food.

Unlike primary burrowers, secondary-burrowing crayfish aren't complete homebodies. Their burrows aren't as complex as those of primary burrowers, and they typically connect to open bodies of water. Secondary-burrowing crayfish spend time in those bodies of water, often during the rainy season, when their burrows become flooded, according to Julian Reynolds and Catherine Souty-Grosset, authors of "Management of Freshwater Biodiversity: Crayfish as Bioindicators." Once the rainy season ends and the bodies of water start drying up, secondary burrowers scurry back into their burrows.

Tertiary-burrowing crayfish aren't too enthusiastic about burrowing. They live the vast majority of their life in open bodies of water, turning to burrows only if their water dries up and they need to find moisture under the surface. They may also burrow to breed. As soon as the bodies of water start filling up again, tertiary burrowers hurry back out into the open water. While tertiary burrowers and secondary burrowers may seem similar, secondary burrowers spend more time inside their burrows. Also, the burrows of tertiary burrowers are simpler than those of secondary burrowers.