The female brooding her eggs on a nearly vertical rock face at a depth of 1397 meters. (PLOS ONE)

How does she do it? That’s the question scientists are asking after observing an octopus caring for her eggs for 53 months. That’s a record gestation period, they say, for any animal species.

The octopus generally does not feed while brooding, but most don’t brood anywhere near as long. Most don’t even live that long. The previous record for octopus gestation, they say, was 14 months.

They saw no evidence of feeding or of the mother moving away, at least on the occasions while they were observing. “During the periods when we had the female under observation, she never left the eggs unattended; but our presence included only a small fraction of the protracted brooding period.”

“The principal question now remaining,” they write, “is how does the mother survive for so long?”

The observation was reported in PLOS ONE in an article entitled “Deep-Sea Octopus (Graneledone boreopacifica) conducts the Longest-Known Egg-Brooding Period of Any Animal.” The authors are Bruce Robison of the Monterey Bay Aquarium Research Institute, Brad Seibel of the University of Rhode Island and Jeffrey Drazen of the University of Hawaii.

Their story began in April 2007, when they used a remotely operated vehicle to observe a rocky outcrop 1,397 meters (4,583 feet) deep in the Monterey Canyon off of California. While they saw no octopus brooding at that time, they did see “a solitary octopus” moving toward an exposed hard substrate.

They reported revisiting the site in May 2007 and seeing the same creature, which they identified through her unique scars, guarding a clutch of eggs.

In the next four-and-a-half years, they returned to the site 18 times:

Each time we returned we found the same octopus clinging to the vertical rock face, arms curled, covering her eggs. Continuous growth of the eggs provided evidence that it was the same clutch throughout … During the periods when we had the female under observation, she never left the eggs unattended. … While she occasionally shifted her position slightly, or uncurled and lifted one or two arms, the female always remained centered over the clutch of eggs.

The authors note octopods cease or greatly reduce feeding when they brood. The only activity they observed was when she protectively pushed away prey — various crustaceans — as they came within her “watch circle.”

When they returned in October 2011, she was finally gone. “The rock face she had occupied held only the tattered remains of empty egg capsules,” they wrote. They estimated the number at between 155 and 165 eggs. If she was like other octopuses, she went off and died then.

Fifty-three months. Even compared with elephants (20 to 21 months), some sharks (which carry their embryos for 42 months) and alpine salamanders (48 months), that’s long.

It’s conceivable they missed something, they acknowledge. They weren’t observing every minute of every day or even every day. But they don’t think so.

For more on this, see Rachel Feltman’s article in the Post’s Speaking-of Science blog here.