A 2018 expedition to Davidson Seamount captured a rare view of a dumbo octopus in its deep-sea habitat. In footage from the remotely operated vehicle Hercules, the pale animal moves with its large fins and opens its webbed arms into an umbrella-like shape. The encounter is still drawing fresh attention today.
The footage came from the first dive of an expedition aboard E/V Nautilus exploring Davidson Seamount, according to nautiluslive.org. The dive took place within Monterey Bay National Marine Sanctuary and explored a previously uncharted rocky outcropping southeast of the seamount, an area the Nautilus team described as rich in coral and sponge fields. The encounter was also covered by A-Z Animals.
Nautilus Live estimated the animal was about 60 centimeters, or almost two feet, long. Its account describes the octopus moving its fins and spreading its webbed arms, exposing rows of suckers. National Geographic also reported the sighting at two miles below the surface; Smithsonian magazine gave the depth as around 10,500 feet, consistent with Nautilus Live’s account of roughly 3,200 meters.
Why This Octopus Is So Rarely Seen
Dumbo octopuses are seldom encountered, in part because researchers can observe only small areas of the deep ocean at a time. Chad King, the Nautilus chief scientist, told Smithsonian magazine that the odds are low when researchers are working in one little spot. The Natural History Museum describes dumbo octopuses as semi-translucent, with ear-like fins on bell-shaped bodies that give the group its name.
The fins help the animals move: the Natural History Museum says dumbo octopuses flap them slowly and steer with their eight limbs. Webbing between the limbs lets them open and close the umbrella-like shape seen in the footage. Smithsonian researchers have described a combination of fin and arm movements, with limited jet propulsion; fin-powered swimming is a defining trait of the dumbo octopus family. These cirrate octopuses also have tiny finger-like cirri along their arms near the suckers, structures associated with feeding as they search near the seafloor for worms, snails, bivalves, isopods and other small invertebrates.
No Sunlight, No Self-Made Glow
At nearly two miles down, the habitat is essentially black without the submersible’s lights. The footage’s ghostly appearance came from Hercules’s illumination; it did not show the octopus producing light of its own. NOAA has noted that dumbo octopuses generally lack the elaborate color-changing abilities seen in many shallow-water species.
Observations at these depths rely on deep-diving remotely operated vehicles and other specialized equipment. Researchers have recorded dumbo octopuses thousands of feet below the surface, with some observations exceeding 13,000 feet. Davidson Seamount is an extinct underwater volcano about 130 kilometers, or 80 miles, southwest of Monterey, according to MBARI.
A Different Octopus Gathering
The dumbo octopus sighting was not the only octopus discovery in the broader Davidson Seamount area. In 2018, researchers from NOAA's Monterey Bay National Marine Sanctuary and Nautilus Live documented a separate aggregation nicknamed the Octopus Garden, where thousands of pearl octopuses gather to mate and nest near thermal springs. MBARI reports that scientists have counted more than 6,000 octopuses in part of the site and expect the nursery could hold 20,000 or more. Water in the nesting cracks and crevices is warmed to nearly 11 degrees Celsius.
Follow-up dives in the broader Davidson Seamount area have continued to reveal more about its octopuses. A Nautilus Live blog post from 2019 reported baby octopuses inside their eggs and at least five hatchlings.
What NOAA Records Show About Davidson Seamount
The 2018 Nautilus expedition explored a previously uncharted rocky outcropping within Monterey Bay National Marine Sanctuary, and NOAA's sanctuary office notes that repeated visits to the area have revealed at least 18 species new to science. NOAA's Monterey Bay National Marine Sanctuary records that Davidson Seamount last erupted as an undersea volcano approximately 9.8 million years ago, according to NOAA.
