Monk Seal Monday #190: Sleeping Habits of Elephant Seals at Sea

Last year, we shared some of the more unique sleeping places of Hawaiian monk seals reported over the years on Kauai. Those beach spots included alongside logs, chaise lounges, picnic tables, beach mats, and blocks of concrete.

According to NOAA, “[Hawaiian monk seals] usually sleep on beaches, sometimes for days at a time. They also occasionally sleep in small underwater caves.”

Hawaiian monk seals belong to the family Phocidae. Known as “true seals,” phocids are characterized by having no external ears. Another true seal, the elephant seal, was recently revealed to sleep while diving.

According to Science Daily, “The new findings, published April 20 in Science, show that while elephant seals may spend 10 hours a day sleeping on the beach during the breeding season, they average just 2 hours of sleep per day when they are at sea on months-long foraging trips. They sleep for about 10 minutes at a time during deep, 30-minute dives, often spiraling downward while fast asleep, and sometimes lying motionless on the seafloor.”

This video explains:

In one extreme case, a 2010, a Hawaiian monk seal (RO12) was recorded going on 2,000-mile open-ocean journey. While Hawaiian monk seal biology isn’t quite as extreme as elephant seals—they may spend days at sea but not months—could monk seals, too, sleep while diving?

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Field Notes: August 2010

RT12 has his Hawaiian name!  He is Kimo Kai, or “Sleepy Ocean”, named by (and after) vacationing volunteer Jim Maser when RT12 was just a couple of weeks old.   After checking with our Hawaiian cultural practitioners, we have now made it official!

Mahalo-eha (RA36) has been spotted back at his natal beach, Maha’ulepu!

Photo credit: Michele Bane

Love is in the air for Kauai’s seals!  We have seen lots of male-female pairs hauled out, entering, and exiting the water together lately.  Some of these included large adult female RK13 with Oahu/Kauai male RO18; scarred female RK30 with our old, dominant male TT40, seven-time mom RK12 with young adult male R4DI, and Oahu male Kermit (RO12) with an unidentified female.   Even little juvenile Kaikoa (RA00) has been seen several times with subadult male RV18, though this pair is too young to mate!

Kermit (RO12), as mentioned above, has returned to Kauai.  But check out what he was doing this summer!!  He had a 2000-mile journey into the pelagic (open-ocean) realm!

Back on the east shore of Kauai, Kermit lost his cell-phone tag. Thanks to one of our observant and thorough volunteers finding the tag in the sand, we can now learn more about Kermit’s adventure and reuse his tag to track another seal!

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