Diet and Eating Habits
A. Food preferences and resources.
1. Walruses prefer molluscs, mainly bivalves such as clams. They suck bivalve animals from the shells. Walruses also eat many other kinds of benthic invertebrates including worms, gastropods, cephalopods, crustaceans, sea cucumbers, and other soft-bodied animals. Walruses may occasionally prey on fishes such as polar cod.
2. Walruses may eat the remains of young seals when food is scarce.
3. There are some rare but habitual seal-eating walruses. Their diet consists mainly of
ringed and bearded seals. These are usually male walruses, recognizable because they are
usually larger than other males with powerful shoulder and chest muscles. Their skin may
become grease-stained from the blubber of the seals.
B. Food intake.
1. Adult walruses eat about 4.2% to 6.2% of their total body weight per day. They eat less on their northward migration.
2. Observations of feedings indicate that walruses fill their stomachs twice daily.
3. Adults may eat as many as 3,000 to 6,000 clams at a single feeding.
C. Methods of collecting food.
1. Walruses usually forage within 80 m (262 ft.) of the surface. Most feeding probably takes place between 10 and 50 m (33-164 ft.).
2. Because visability is poor in deep and murky waters, walruses rely on their vibrissae to locate food.
3. A walrus moves its snout along the bottom, rooting through the sediment. Abrasion patterns of the tusks show that they are dragged through the sediment, but are not used to dig up prey.
4. Evidence shows that walruses may also take in mouthfuls of water and squirt powerful
jets at the sea floor, excavating burrowing invertebrates such as clams.
A Walrus squirts a powerful jet of water at the sea floor
to excavate burrowing invertebrates.
5. Walruses do not chew their food, but they do sometimes crush clam shells.
a. Soft-bodied invertebrates are usually not crushed or torn. A walrus sucks off the foot and the fleshy siphon of a clam and swallows it whole.
b. The cheek teeth do get worn, but this is probably from abrasion by minute particles of sand that walruses inadvertently take into their mouths and not from crushing clam shells.
6. Researchers have found numerous pebbles and small stones in the stomachs of
walruses. They are thought to be ingested while feeding.
