Chambered nautilus

The nautilus sniffs out its food.

It eats crabs, shrimp, fish and dead animals it finds. Its tentacles grab the food and pass it to its mouth.

The nautilus is a hunter and a scavenger. It eats shrimp, crabs, lobsters, fish and the remains of dead animals.

Its eyes are not very sharp, so it finds food mostly by smell. Special sensing cells on its tentacles pick up scents in the water. The tentacles grab the food and pass it to a hard, beak-like mouth, which tears it into pieces.

Nautiluses are nocturnal, opportunistic feeders. NOAA Fisheries lists fish, crabs and lobsters as prey, and the Aquarium of the Pacific adds shrimp, carrion and, occasionally, other nautiluses; the Australian Museum describes N. pompilius as a scavenger and opportunistic predator feeding mainly on crustaceans.

Prey is located chemically rather than by sight: chemosensors on the inner surface of the suckerless tentacles detect odors in the water. Food is passed to a beak-like jaw, and the radula, a file-like ribbon of teeth, shreds it further before swallowing. Trapping studies catch the most nautiluses on silty or muddy slopes below reef walls, which Dunstan and colleagues (2011) suggest are good places to scavenge.

In the day, the nautilus stays deep down.

At night it swims slowly up the reef wall. It sniffs around for food, then goes back down before morning.

Nautiluses travel up and down reef slopes rather than across the ocean. Many spend the day resting deep down and rise at night to hunt, then sink back down around sunrise.

Scientists once thought every nautilus followed the same simple pattern. When researchers tracked nautiluses with small tags and filmed them with underwater robots at Osprey Reef, off Australia, they found something more complicated: some rested around 200 meters by day while others hunted much deeper, and at night they kept moving up and down.

Daily vertical migration was long assumed to be universal: deep by day, shallow by night. Using ultrasonic transmitters on eleven N. pompilius at Osprey Reef in the Coral Sea, plus remotely operated vehicle dives, Dunstan, Ward and Marshall (PLoS ONE, 2011) found nearly continuous nightly movement between about 130 and 700 meters. By day, animals either rested at about 160 to 225 meters or foraged at 489 to 700 meters.

The authors link these patterns to food on silty slopes, avoiding daytime predators, temperature limits and buoyancy: below about 250 meters liquid seeps into the chambers, so a nautilus must return shallower to pump it out. They suggest different populations may use different strategies.

Some people catch nautiluses to sell their pretty shells.

Nautiluses grow up slowly, so it is hard for them to catch up. Now there are rules to protect them.

The biggest danger for the chambered nautilus is being caught for its beautiful shell. The shells are sold as souvenirs and made into jewelry and decorations. Because nautiluses grow slowly and lay few eggs, a fished area can lose its nautiluses for a very long time.

In 2016, countries agreed to control the international trade in all nautiluses under a treaty called CITES. In 2018, the United States listed the chambered nautilus as threatened, and the IUCN Red List now lists it as Vulnerable. Choosing not to buy nautilus shells helps too.

NOAA Fisheries names harvest for the international shell trade as the primary threat; shells are sold whole or cut for inlay in jewelry and decor. Its 2016 fact sheet reports declines where targeted fisheries exist or existed, including India, Indonesia, New Caledonia, the Philippines and possibly Palau, with one population's trap yields falling 97 percent in 16 years. Fishing tends to move on to new sites as each is depleted.

At CITES CoP17 in 2016 the Parties added the whole family Nautilidae to Appendix II, following a proposal by the United States, Fiji, India and Palau. NOAA Fisheries listed N. pompilius as Threatened under the Endangered Species Act in 2018. Its first IUCN Red List assessment (assessed 2023, published 2026) rates it Vulnerable (criterion A3d), with a decreasing population; within it, the Indonesian subspecies is assessed as Endangered and the Philippine subspecies as Critically Endangered, because of heavy fishing.