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Biology/Natural History: Farther south this species grows individually, but here in the Pacific Northwest aggregations can sometimes be so dense that the thatched appearance is not immediately evident. The barnacles grow very tall and narrow when densely aggregated. Competitors for space include Halichondria panicea (crumb of bread sponge), Mytilus trossulus, and Mytilus californianus. When the barnacles are small they may be bulldozed off the rocks by grazing limpets such as Lottia digitalis. The large size of adults likely protect them from some predators such as Nucella lamellosa or the seastars Pisaster ochraceous and Pycnopodia helianthoides. Eggs are brooded in the winter and the cyprid larvae settle in the spring (fall and winter on the open Washington coast). The larvae preferentially settle near adult barnacle shells. Lifespan up to 15 years.
These barnacles appear to have been eaten by native tribes in SE Alaska in some coastal locations during an extended time period. At other times, mussels were a more common food in the same regions.