Named for the rows of small knobs that run along its shell, this predatory snail is a common resident of sandy bays and harbours. The knobs are not just decorative. They strengthen the shell, making it more resistant to the crushing attacks of crabs and other predators. The shell is also thick and heavy, a sturdy fortress for the soft-bodied animal inside. The knobbed whelk is a predator. It uses its long proboscis to drill holes into the shells of cockles and other bivalves. The proboscis is tipped with a radula, a tongue-like organ covered in tiny teeth. The whelk uses its radula to scrape a hole through the shell, a process that can take hours or even days. Once the hole is complete, the whelk inserts its proboscis and scrapes out the soft flesh inside. The empty shell is left behind, a neat, circular hole marking the site of the kill. It also scavenges on dead animals, playing an important role in cleaning the seafloor. A dead fish on the bottom of the harbour will attract knobbed whelks from across the bay. They gather in numbers, crawling slowly across the carcass, using their proboscises to tear off pieces of flesh. Within a few days, the fish is gone, reduced to bones and scales by the whelks and their fellow scavengers. Its shell is a common find on sandy beaches, often with a small, neat hole drilled into a neighbouring cockle shell. Beachcombers call these shells the evidence of a crime scene. The cockle was alive, the whelk was hungry, and the hole tells the story. The knobbed whelk is not commercially harvested in New Zealand, but it is sometimes collected by shell collectors for its attractive, knobbly shell. Its role as a predator of cockles and other bivalves makes it an important part of the estuarine ecosystem. Without whelks, cockle populations could explode, depleting their own food supply. The whelk keeps the system in balance.