If anyone ever asks you, “What is the rarest crayfish in the state of West Virginia?”
You can tell them, “Well that is difficult to say, but a good candidate would be the digger crayfish, Fallicambarus fodiens.”
You might win a pub trivia bet with that. Under a particularly bizarre set of circumstances.
I know this not because it is part of my general background knowledge, but because I was checking a new paper by Loughman and colleagues on burrowing by crayfish. Burrowing crayfish are very hard to study, like many digging and burrowing animals are. You need a lot of effort to pull them up out of their burrows.
This paper did both collection and modelling for F. fodiens and another burrowing species, the little brown mudbug (seriously, that’s its official common name), Cambarus thomai. For the digger, one of the best predictors of whether you could find this species was whether the surrounding forest was over one hundred years old.
The odd thing is, this relationship with old growth forest seems specific to West Virginia. The authors note that you can find digger crayfish in other states in “in roadside ditches, residential situations, and agricultural settings.” The authors suggest that in West Virginia, the little brown mudbug outcompetes the digger crayfish in disturbed habitat, and the little brown mudbug doesn’t live everywhere that the digger does.
It does help point out, however, that not all forests are the same. Sometimes, you have to keep the old, old stuff around.
Loughman ZJ, Welsh SA,Simon TP. 2012. Occupancy rates of primary burrowing crayfish in natural and disturbed large river bottomlands. Journal of Crustacean Biology 32(4): 557-564. 10.1163/193724012X637339