Blue crayfish prefers living underground

May 12, 2008

Crayfish that are native to open-water areas such as streams and rivers are often colored similarly to their surroundings as a camouflage mechanism.

A reader recently asked for help in identifying the small blue shell of a crayfish she found on a hillside dozens of feet from the nearest stream, while hiking in southwestern Pennsylvania.

Challenge-proof identification is not possible as the reader did not save the shell or get a photo of it, but it sounds like the shell of Cambarus monongalensis, which is also known as the blue crayfish.

Unlike some of the more familiar species, the blue crayfish is a burrowing crayfish and does not need to remain in or close to water. It digs into wooded hillsides, springs and seeps, usually topping the burrow with an external, funnel-shaped, mud chimney that catches rain water and channels it to underground pools.

It's one of 13 species of crayfish believed to be native to Pennsylvania. There might be more; crayfish are not a heavily researched or surveyed group of animals.

In addition, at least two nonnative species have been introduced to the state. They are the rusty crayfish and the northern crayfish.

While burrowing crayfish are generally less familiar and usually less commonly spotted because they spend so much of their time underground, they also can be some of the most brightly colored. Open-water crayfish species are generally dully colored -- similar to the rocks, mud, grasses and such in their environment -- as a protective, camouflaging mechanism for eluding predators.


1. North America is home to about A. 200, B. 400 or C. 600 species of crayfish.

2. True or false? A square meter of stream in Pennsylvania can hold as many as 25 crayfish.

3. Can you describe the niche that crayfish fill in their ecosystems?


1. B. About 400 species; 390 is the number most often cited.

2. True.

3. As midlevel predators/scavengers, crayfish help to move energy up through the food chain.


Gather a few crayfish from a local stream and try to identify them using the key at key[underscore]to[underscore]pa[underscore] crayfishes.htm. MARCUS SCHNECK: 610-562-1884 or Schneck's outdoor writing also appears Wednesday and Sunday in Sports and regularly in his blog, Wild About PA, at

Caption: Crayfish that are native to open-water areas, such as streams and rivers, are often colored similarly to their surroundings as a camouflage mechanism.

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