Maybe it has something to do with their shells?
According to the June issue of In-Fisherman and their bass research article, bass will not eat small turtles but simply spit them back out during their tests. Supposedly bass do not like the sensation of the turtles clawing around in their mouth and stomachs and I probably wouldn't either . Bass will also supposedly not eat toad tadpoles nor will they eat bullfrog tadpoles and quickly learn to tell the difference and avoid them unless they are starving. They will readily eat leopard frog tadpoles though. This is according to some in-depth scientific studies done recently by men far wiser than me.
sorry I must have missed that post. just seems odd that they'll eat a crawfish with pincher's. doesn't it ?