# Nautilus — Facts, Threats & Conservation

*Nautilus pompilius (Linnaeus, 1758) — family Nautilidae; genus Nautilus among six living nautiloid species*

> The chambered nautilus (Nautilus pompilius) is a nocturnal Indo-Pacific cephalopod with an external coiled shell and pinhole eyes; it adjusts buoyancy with gas-filled chambers, is listed Vulnerable due to shell trade and slow reproduction, and represents an ancient nautiloid lineage.

**IUCN status:** Vulnerable (IUCN 2018) — chambered nautilus; threatened by shell trade and slow reproduction  ·  **WARN range:** Indo-Pacific coral reefs and slopes, Philippines, Papua New Guinea, Australia and neighbouring waters

## Quick facts
| Fact | Value |
| --- | --- |
| Shell diameter | Roughly 20–25 cm in large N. pompilius |
| Diet | Scavenging and small prey at night |
| Habitat | Deep Indo-Pacific reef slopes |
| Eye | Pinhole — no lens |
| IUCN status | Vulnerable (Nautilus pompilius) |
| Trade | CITES Appendix II |

## Scientific classification
- **Kingdom:** Animalia
- **Phylum:** Mollusca
- **Class:** Cephalopoda
- **Subclass:** Nautiloidea
- **Family:** Nautilidae
- **Genus:** Nautilus
- **Species:** Nautilus pompilius

## Conservation status
- **Status:** Vulnerable
- **Population:** No reliable global estimate — declining in heavily fished areas
- **Trend:** Decreasing
- **Assessed:** 2018
- **CITES:** Appendix II
- Shell collection for curio and jewellery trade is the primary documented threat. Slow reproduction limits recovery.

## Key facts: Nautilus
- Nautiluses are cephalopods with external coiled shells — the only living group to retain one.
- Nautilus pompilius is listed Vulnerable, threatened by shell collection and slow life history.
- Eyes are pinholes without lenses — adequate for low light but not comparable to octopus vision.
- Buoyancy is controlled by gas and fluid in shell chambers connected to the living chamber.
- They are nocturnal scavengers on deep reef slopes, rising toward shallower water at night.
- CITES Appendix II listing restricts international trade in nautilus shells.

## Shell, chambers and buoyancy
The nautilus shell is a logarithmic spiral divided by septa into chambers. The animal occupies only the outermost chamber; earlier chambers are sealed and filled with gas and fluid regulated through a siphuncle tube. Adding gas or removing liquid changes buoyancy without constant swimming effort — a solution octopuses abandoned when they internalised or lost the shell entirely.

The shell is also armour. Predators include sharks and large fish; the hard exterior survives attacks that would finish a soft-bodied octopus. Trade demand for that same shell is now the primary human threat.

## Pinhole eyes in a cephalopod class built for vision
Octopuses and cuttlefish evolved camera eyes with lenses capable of forming sharp images. Nautiluses did not. Their eye is a simple pinhole aperture — no lens, no cornea — producing a fuzzy image adequate for detecting contrast and movement in dim reef light at depth.

Because they are nocturnal scavengers rather than diurnal hunters of fast prey, that may be sufficient. It is also a window into deep time: nautiloid eyes represent an earlier stage before cephalopod vision escalated. Living nautiluses are not primitive — they are successful survivors — but they carry ancestral traits side by side with modern ones.

## Slow life history meets shell trade
Nautiluses mature late and lay few eggs — often a dozen or fewer per year in some species, attached to hard substrate in deep water. Population recovery from fishing is slow. Harvest for shells — whole specimens for the curio trade, polished sections for jewellery — removes breeding adults directly.

IUCN assessed Nautilus pompilius as Vulnerable in 2018, citing trade-driven declines in the Philippines and other range states. CITES Appendix II regulates international export. Enforcement and bycatch in deep reef fisheries remain ongoing problems. A shell on a shelf is often a removed adult that will not be replaced quickly.

## Ancient lineage, modern ocean
Nautiloids appear in the fossil record roughly 500 million years ago and were major predators of Palaeozoic seas. Ammonites — extinct relatives with more elaborate sutures — dominated the Mesozoic until the end-Cretaceous extinction. Nautilus is the familiar living remnant of that radiation, not an ammonite itself but a cousin that persisted.

Deep slopes and night feeding kept nautiluses off many human radars until scuba and trade demand exposed them. Climate change and ocean acidification may weaken shell formation over time, stacking pressure on a group already hit by direct harvest.

## What WARN does
WARN publishes free marine species education for animals traded as souvenirs without buyers understanding life history. Nautilus shells in shops represent slow-reproducing adults removed from reef slopes — the Vulnerable listing is a direct response to that market.

If this guide helps you understand wildlife and the pressures it faces, a gift to WARN supports habitat protection and free public education in our partner countries.

## Frequently asked questions: Nautilus
### What do nautiluses eat?
Nautiluses are scavengers and opportunistic predators, eating crustacean moult remains, carrion and small live prey such as crabs and fish at night on reef slopes. They use tentacles — up to 90 without suckers — to deliver food to the beak.

### Where do nautiluses live?
Indo-Pacific coral reef slopes and deep reef habitats, typically from about 100 m to 500 m by day, rising to shallower water at night. Nautilus pompilius occurs from the Philippines and Indonesia to Papua New Guinea, Australia and nearby waters.

### Are nautiluses dangerous to humans?
No. They are slow, nocturnal and not aggressive toward divers. The beak can bite if handled, but they are not venomous and pose no meaningful risk in ordinary encounters.

### How long do nautiluses live?
Estimates often cite 15–20 years or more, but precise longevity in the wild is poorly documented because of depth and tagging difficulty. Slow maturity and low fecundity make population recovery slow regardless of exact lifespan.

### How big do nautiluses get?
Nautilus pompilius shells commonly reach roughly 20–25 cm in diameter in large adults. The soft body occupies only the outer chamber; most of the visible shell is empty buoyancy space.

### Are nautiluses endangered?
Nautilus pompilius is listed Vulnerable on the IUCN Red List, primarily due to overcollection for the shell trade. CITES Appendix II restricts international trade. Status varies among the six living nautilus species.

## Sources
- [IUCN Red List — Nautilus pompilius](https://www.iucnredlist.org/species/163226A998522)
- [CITES Appendices](https://cites.org/eng/app/appendices.php)

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Full guide: https://worldanimalrescuenetwork.org/wildlife-guides/nautilus