Nautilus Swims Up to Submersible at 365 Meters Near Fiji

Q: What drew a prehistoric, deep-sea nautilus to directly investigate a human submersible in the dark twilight zone?

Scientists do not know for certain what drew the nautilus in, but the most plausible explanation is curiosity triggered by the submersible’s unusual presence in a dark environment where such large objects are rare. The animal was seen resting on the seafloor about 365 metres down, then rose and swam straight toward the vehicle, hovering beside the glass dome at eye level. Whitney Goodell of National Geographic Pristine Seas said it appeared to be investigating the researchers as much as they were observing it. Because natural encounters like this are uncommon, there is no direct evidence that a single factor—such as light, sound or smell—caused the approach. What is known about nautiluses supports the idea that the submersible stood out strongly in the twilight zone. Nautiluses live in a narrow “Goldilocks” depth range and use their shell chambers for buoyancy. They also rely heavily on sensory cues in dim water, especially chemical signals detected with tentacles, to locate food and navigate. A bright, noisy, unfamiliar object moving through their habitat could therefore have prompted an investigative response. Researchers stressed that this was notable precisely because nautiluses are usually recorded on baited cameras rather than encountered spontaneously in the wild. The moment offers a rare glimpse of natural nautilus behavior and underscores how little is still known about life in deep-sea habitats that are increasingly seen as important for conservation.

1 articles · Updated · BBC Discover Wildlife · Jul 31

Researchers exploring near Rotuma, about 300 miles north of Fiji, said a nautilus lifted off the seafloor at 365 meters and hovered at the submersible’s glass dome.
Whitney Goodell of National Geographic Pristine Seas said the animal appeared curious as the team approached, and scientists used their phones after it moved out of the vehicle cameras’ frame.
Nautiluses are rarely encountered by chance in their natural habitat; Goodell said researchers more often spot them on baited camera footage.
The molluscs live in an ocean “Goldilocks” zone several hundred meters down, where water is cool enough but pressure is not yet high enough to crush their gas-filled shells.
The sighting also underscored the importance of protecting underwater banks and other deep-sea features that support nautilus movement and survival.