Red Rock Crab (Cancer productus)

Description: As its name suggests, this crab is brick-red in color, although juvenile red rock crabs range from white to dark, with the darker juveniles sometimes having a white-striped pattern on their shell. Red rock crabs are most clearly identified by their black claw tips. These crabs are widest at the 8th spike and have 9 spikes total on each side. They also have 5 small spikes in between their eyes. Males tend to be about 20 cm wide, and females are usually 17 cm wide.

Habitat: The red rock crab is found along the Pacific Coast of North America from Alaska down to Mexico. Along these coastlines, it prefers habitats with rocky and soft sediments.

Diet: In their rocky and sandy habitats, red rock crabs hunt for invertebrates to eat, such as snails, clams, barnacles, and more. Predators of red rock crabs include certain fish and seabird species. 

Reproduction: Similar to Dungeness crab, males with hold onto a female that is getting ready to molt. Red Rock crab males with often hold the female underneath them face to face, instead of on the back like Dungeness. Once the female molts, they will mate and the male with stay with her until her new shell has hardened. She can then have between 172,000 to 597,000 eggs that she’ll carry under her apron.

Tide Pool Tidbits:

• Red rock crabs have one of the strongest pinching forces compared to other crabs! This helps them break through the shells of the mollusks and crustaceans they eat. Some studies have even found that crabs that eat thick-shelled species like our California mussel often develop stronger claws.

• Sometimes, juvenile red rock crabs can be mistaken for Dungeness crabs (Metacarcinus magister). One way to tell these two species apart is to see where their carapace (their shell) is the widest. On a Dungeness crab, the carapace is widest at the 10th (and last) tooth back from the eyes. On a red rock crab, the widest point lines up with the 8th (second to last) tooth on the carapace.

Reference: Walla Walla University