This whelk is carnivorous, and feeds on polychaete worms and other molluscs, such as bivalves. It uses the edge of its shell to prize open bivalve shells (2), and may drill holes into the shell of its prey in order to access the soft tissues inside. It also scavenges for carrion, which it detects by smell from some distance (2). When searching for food, whelks extend a tube known as the 'siphon', which is used to funnel water to the gills, and leads to a sensory organ used for smelling prey (4).
The sexes are separate; breeding takes place from October to May, and the eggs are attached to rocks, shells and stones in protective capsules. Each capsule contains as many as 1000 eggs, and the capsules of several females are grouped together in large masses of over 2000 (2). Only a few of these eggs will develop; most eggs are used as a source of food by the growing embryos (3). There is no free-swimming larval stage (4), instead, crawling young emerge from the capsules after several months (3). Empty egg masses frequently wash up on beaches, and are often mistaken for sponges (2). They are known as 'sea wash balls' because they were once used to wash with (3).
Common whelks are thought to live for 10 years. They are fished commercially using traps; most whelks are exported to the Far East (2).