The Weddell Seal

Weddell mom and pup (From IcySeals gallery)
Current conditions:  Con3. Temp 16ºF (wind chill 7ºF).  Mostly cloudy (some flurries). 
Population = 726

Aside from friends and family, there are two things I desperately miss down here: furry animals (particularly my own dog and cat, but really, anything pet-able) and the spectrum of nature's colors (particularly green).  There is no hope for the latter--grey, brown, white and blue is all I'll see for six months.  With respect to the former, we have some relief.  We get to see--though not pet--seals.

Three types of seal come through the McMurdo area:  the Leopard, the Crabeater and the Weddell.  A leopard dragged an Antarctic biologist underwater 15 years ago, killing her.  They've also, on rare occasion, attack humans on the ice.  So that's a furry creature I prefer to avoid.  Crabeater seals--which don't eat crabs--are rarely seen.  The most populous of all seal species, they spend their time out on pack ice off the coast.  Weddell seals, however, are downright sociable.  At peak summer season, when the females are welping, they hang out on the ice right next to McMurdo and Scott base, looking a whole lot like 1200 pound slugs. Their docility made them favorites of the Antarctic Explorers.  By "favorites", I mean favorite dinner items (see Sept. 16th blog).  One half-ton seal provides lots of human and dog meals that are rich in vitamin C,  preventing the scurvy, the scourge of Antarctic explorers.

Newborn lying on the ice (picture from IcySeals)
There are three "seal teams" down here.  They, too, love seals but not in the culinary sense.  The IcySeal team, which presented at our Sunday lecture two weeks ago, tries to understand how Weddell seal pups survive the cold (go to the IcySeals gallery for some wonderful pictures of seal pups).

Here are some seal factoids:
  • Where ice is unstable (the Arctic), baby seals are weaned extremely quickly.  Some seal pups have only a few days before their mothers head out to sea, leaving them to fend for themselves.  Where the ice is more stable (the Antarctic), babies and moms are together for much longer (6-8 weeks for Weddells, 2-3 weeks for Crabeaters).
  • Seal pups have two ways of protecting themselves from the cold:  blubber and lanugo fur.  Some seal species are born with extraordinary amounts of blubber and other species are born quite furry.  The Weddell seal pups are neither furry nor blubbery, making them of physiologic interest.  It's a mystery why the pups don't freeze to death on the ice.
  • Weddell seal pups start swimming tentatively after a few weeks.  When grown, they dive as deep as 2000 feet and stay underwater for as long as 90 minutes (California's elephant seals remain the champions of deep diving at a record 7,800 feet).  Like other deep divers, they can store much more oxygen (87 ml per kg) than humans (22/ ml per kg), with lots of O2 in muscle  and little in lungs (they exhale before they dive).
  • Weddell seals (and many other seal species) breed soon after giving birth.  Implantation of the fertilized egg in the uterus, however, does not occur for months (delayed implantation).  Gestation is only 9 months but the time from successful breeding to birth is 12 months.
  • Weddells make wonderful sounds underwater.  If you go to the MOO website (see link at upper left of blog), you may be able to hear them.  To me, it sounds a lot like whale songs.
  • Weddell seals have to have an exit hole through the ice to breathe after their dives (see below). Often, the males are quite protective of their holes and will chase other animals away.  Sometimes, pups actually drown for want of a hole.  Fortunately, Weddells have projecting front teeth to chew a hole in the ice if they can't find another way out.
Picture by Rebecca of seals near Scott Base.  Note the newborn blob on the right, next to the adult blobs. 

Humans also need exit holes when they dive.   On occasion, just as the diver is about to enter the water from their dive hut, a Weddell seal pops up to use the perfectly sized ice entry as their breathing hole.   Since it is strictly forbidden to interact with the animals, the diver has to wait in the hot dry suit in the heated dive hut for the seal to decide to re-enter the water.  Even worse, the seal can occupy the hole when the diver wants to get OUT of the water.  Divers coming back from collecting specimens only to have their egress blocked by a Weddell seal butt.  And they have to wait.  And wait.  And wait.

Seal in dive hole by Shaun OBoyle (stolen from internet)
The lecturer Sunday had this exact experience.   She had been out collecting specimens only to find a seal blocking her hut's dive hole.  After a seemingly endless time (probably just a few minutes), getting colder and colder in the sub-zero water, the seal finally swam off.  Climbing back into the hut, they found the hut's dive tender--who helps them in and out of the water--doubled over with laughter.  She had taken a video of the seal hanging out in the hole.  Right before leaving, it had puked a voluminous amount of gelatinous goo over the water surface that coated the divers with puke as they came out of the hole.  Is that funny?  I guess in retrospect.  It definitely tickled the audience in that "ooh, gross" kind of way.

Seal blobs off of Hut Point. Note that they are lined up along the pressure ridge.  The small cracks in the ice
allow them to readily get in and out of the water.  I stared at these seals for 30 minutes, never
observing even a twitch of a flipper.  They must move, though, because the next day, they were all gone.




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