Striped Shore Crab

Pachygrapsus crassipes andHemigrapsus oregonensis coexist in California tidal marshes with overlaping foraging spaces and burrowing distrubitions. P. crassipes will prey andutilizes H.oregonensis burrows after.

Pachygrapsus crassipesoccupy exposed rock areas during the daytime. P. crassipesare very inactive and show very little aggresion during this period unless disturbed in which they utilize their rearing defense posture.

When moving on the rocky terrain, P. crassipeshave been observed to utilized slow walking speeds and narrow stances. The narrow stance is used to maximize the distance between the body and the rocky surface. These behaviors are used by the crab to reduce the risk of accidential damage to appendages or carapace from a mis-step on the rocky terrain.

The habitat of Pachygrapsus crassipes extend from upper lower intertidal zone to high intertidal zone. When exposed,P. crassipes can be maintained out of the water up to four days.

Thevision of thePachygrapsus crassipesis an important ability to have when walking on the rock surface of the tide pools. Their eyes are able to elevate and rotate on their stalks to fully maximize their vision when moving. But since the eyes are located anteriorly and theP. crassipes walks sideways, the vision might be impaired when on the rocky surface. An adjustment is the forth leg of the crab is located on the opposite end of the body from the eyes. These legs can be utilized as tactile feedback when walking backwards where the eyes are impaired. This tactile feedback is useful on the rocky surface and when seeking refuge.

Pachygrapsus crassipesare considered to have omnivorous feeding habits. They have been observed to eat other crabs, fish, and also graze on algae. These crabs are active scavengers in tide pools during the night time.

Pachygrapsus crassipesandHemigrapsus nuduslook very similar but the H. nudus has red spots on the chelipeds. P. crassipes has the dark green color and transverse striations whileH. nudus does not.

P. Crassipes is a highly aggressive and solitary crab, although not very territorial. When out of water, P. Crassipes’ aggression is subdued, and multiple P. Crassipes will coalesce in moist crevices of rock, sand, et cetera. When aggregated in niches of rock, P. Crassipes is mostly inactive. However, in tide pools, P. Crassipes displays very different behavior, and will not share space with other P. Crassipes. P. Crassipes moves sideways, like other crabs, but is also capable of moving forward at quick speeds.

Pachygrapsus crassipes are opportunistic omnivores and have been observed to prey on Hemigrapsus oregonensis during field observations and laboratory experiements in Santa Barbara, California.

Pachygrapsus crassipes are very activein tidepools where they occupy fissures but are constantly foraging even during the daytime.

The larger P. crassipes crabsare dominant over the smaller ones and the males are more aggressive than the females.