The main predators on P. lividus in the Mediterranean Sea are the spider crab (Maja crispata), the fish Diplodus sargus, Diplodus vulgaris, Labrus merula and Coris julis and the gastropod, Hexaplex trunculus. The spiny starfish (Marthasterias glacialis) is a main predator elsewhere. Predation is dependent on size; juvenile urchins are more vulnerable as their spines are less formidable. In most locations the urchins are nocturnal feeders, but where predators are more active at night the urchins may feed during day instead.
