Feeds as a predator or primarily a scavenger. Can crawl well on rock, or on top of or just below the surface of sand or mud. They crawl with both sides of the large foot, leaving a distinctive track in the sand. Attracted from long distances by rotting meat, which it can smell with its long proboscis. It can crawl rapidly. When feeding, it wraps its foot completely around the food until it is consumed. May also drill in clams or snails. Predators include the seastar Pisaster brevispinus
. When contacted by P. brevispinus
, N. fossatus
may writhe so violently with its foot that it twists into somersaults and even vaults into the water column. At other times it may simply turn and crawl swiftly away, rocking its shell back and forth. Sometimes the colonial hydroid Clytia bakeri
, which is one of few hydroids that grow on exposed sandy shores, is found growing on shells of this species. Deposits its egg capsules on eelgrass or other firm objects in mud flats in late winter and spring. A typical string of eggs may be 6 cm long and contain 45 eggs. The individual capsules are about 3 mm long. They are laid overlapping one another to produce a "shingled" appearance.
The wicker-basketlike appearance of the intersecting radial ribs and spiral ridges is the reason this species is called a basket whelk.