Sea urchins, including this purple sea urchin (Strongylocentrotus purpuratus) will use their tiny tube feet to grab and cover themselves in pieces of algae, small rocks or shells. It is thought that this behavior protects urchins from drying out in tidepools, getting eaten by seagulls, or being damaged by the sun’s ultraviolet rays.

[Photo and caption contributed by Karli Chudeau]

Reference
Douglas, C.A. (1976). Availability of drift materials and the covering response of the sea urchin Strongylocentrotus purpuratus (Stimpson). Pacific Science, 30(1) 83-89.