This red rock crab (Cancer productus) has created a well camouflaged hiding place by digging into the substrate.
Red rock crabs have large claws tipped in black, and a wide reddish carapace. Juvenile red rock crabs are variable in colour and pattern, and some juveniles may have striped markings.
A female red rock crab will release a pheromone letting males know she will soon be ready to molt and mate. Mating can only occur after the female has molted and is soft-shelled, so a male may hold onto his partner for up to a few weeks until her molt takes place. After mating, the male will continue to embrace the female and protect her until her new exoskeleton has hardened.
This crab is a hungry predator and uses its large strong claws to open the shells of other invertebrates like snails, clams, mussels, barnacles, and even unwary smaller crabs. Males can reach a carapace width of 7.8 inches (20 cm), and females grow to 6.6 inches (16.8 cm) across. The red rock crab has a range from Kodiak, Alaska to northern Mexico.
Reference:
Jensen, Gregory. Crabs and Shrimps of the Pacific Coast: A Guide to Shallow-Water Decapods from Southeastern Alaska to the Mexican Border. Bremerton: MolaMarine, 2014.