How to Distinguish from Similar Species: This is one of the two large local Cancer crabs with black tips on their chelae. The other, Cancer productus, has a rough dorsal surface on its carapace and a few tubercles and has no ventral red spots. Its carapace is also produced (projected) forward between the eyes. Other Cancer crabs with black chelae, such as Glebocarcinus oregonensis, have a tuberculate carapace which is usually less than 6 cm wide and is not 1.5x or more as wide as long.
Note: Species formerly in genus Cancer have been recently subdivided into several genera (Ng et al., 2008; Schweitzer and Feldmann, 2010). Of our local genera, Cancer, Romaleon, and Metacarcinus have a carapace wider than long plus only scattered setae on the carapace margins and legs while Glebocarcinus has a carapace of approximately equal length and width, often with granular regions and with setae along the edges; and setae on the outer surface of the chela as well as on the legs. Metacarcinus can be distinguished from Cancer because Metacarcinus has anterolateral carapace teeth which are distinct and sharp plus the male has a rounded tip to the telson, while Cancer has anterolateral carapace teeth which are low, lobed, and separated by deep fissures plus the male has a sharply pointed telson (Schram and Ng, 2012). Romaleon can be distinguished from Cancer and Metacarcinus because it has a distinct tooth on the anterior third of the posterolateral margin of the carapace while the other two genera do not.
Geographical Range: British Columbia to Cabo San Lucas, Baja California but rarely seen north of Coos Bay, Oregon. (But common in Barkley Sound on Vancouver Island)
Depth Range: Intertidal to 91 m, usually less than 45 m.
Habitat: Common in the low rocky intertidal. Often found under rocks, sometimes partly buried in sand under the rocks. Subtidally may be on gravel bottoms or in kelp beds. Especially common on the exposed coast.
History: Food includes
scavenged bits and animals such as Chlorostoma
funebralis and hermit crabs. It captures
the hermit crabs
by gradually chipping away the edges of the hermit's shell until the
crab has nowhere else to hide. Sometimes harvested by humans
crab legs. In California, become mature in about 2
(egg-carrying) females are most often seen November to
young have vivid color patterns on the carapace
similar to those of C. productus young. Most active at night.
Kozloff 1987, 1996
Smith and Carlton, 1975
General Notes and Observations: Locations, abundances, unusual behaviors:
Authors and Editors of Page:
Dave Cowles (2007): Created original page