This crab is a feisty little fellow who will rear up and defend itself when threatened. This fighting position, although brave, provides the lobster with many flaying appendages to grapple. In contrast, a close relative of the rock crab, the Jonah crab, Cancer borealis, is not favored by the lobster. When threatened, the crab will tuck in its appendages and settle into the bottom, giving the lobster very little to grasp.