Interesting

Red sea urchins are among the dominant members of the communities that inhabit rocky reefs from the low intertidal zone to about 90 m. As they feed primarily upon kelp, these urchins tend to aggregate near kelp beds, avoiding areas that may be subject to extreme wave action. When kelp and drift seaweed are abundant, red sea urchins often stay in the same place, using their tube feet to keep a grip on their rocky home as they feed. Juveniles may congregate beneath the spines of adults for protection from predators and possibly food. However, when juveniles reach about 4 cm in diameter, they venture out to acquire food across the rocky environment.