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Thursday, April 4, 2013

Steller view

The Stewards of the Coast and Redwoods is starting a seabird monitoring program.  Yesterday I attended a short training session at one of the sites they'll be monitoring at the southern end of Bodega Head.  Looking south from this spot you can see Bodega Rock, about 2000 feet offshore.

Although we were mostly there to practice counting seabirds, this is also an important haul-out site for sea lions, so we counted them, too.

From a distance, as in the image below, it can be hard to pick out individual sea lions at first.  At one point we all heard a loud roar coming from the island.  This told us that a male Steller Sea Lion (Eumetopias jubatus) was active.

If you focus carefully in the center of the image below...just above the darkest layer of rock...and just below four finger-like rock projections...you may be able to see two very large sea lions.  (If not, I'll follow up with a zoomed in image.)

Here's a closer view:

Notice the two sea lions in upright positions (male on the left and female on the right).  You might be wondering how to identify them as Steller Sea Lions rather than California Sea Lions.  [In general, California Sea Lions are much more common than Steller's, and they're the ones you're more likely to see and the ones you hear barking throughout the Bodega Bay area.]

I like the basic description in Whales, Dolphins, and Other Marine Mammals of the World by Shirihai and Jarrett (2006).  (Steller Sea Lions are also called Northern Sea Lions.)  "Northern Sea Lions are most likely to be confused with California Sea Lions, but Northern is larger, with longer/broader neck, broader head with compressed muzzle, and much flatter crown in bulls (no sagittal crest), as well as generally much paler pelage [fur] and perhaps longer foreflippers."

Here's another view showing the same two individuals, but also revealing more California Sea Lions to the left for comparison.  Note that there are at least a couple of other Steller Sea Lions lying down (the much paler individuals), but most of the other sea lions are smaller, more slender, and a deep red-brown color, telling you that they're more likely to be California Sea Lions.

Central California is at the southern end of the Steller Sea Lion range.  Although they used to breed on the Channel Islands, Año Nuevo Island is now the southernmost rookery site. 

Some day I'll try to record their lion-like roar.  If I'm successful, I'll post an audio recording here.

P.S.  Steller Sea Lion is currently listed as a federally threatened species, but last year NMFS proposed to remove them from the endangered species list.  You can read more about them here.

P.P.S.  For more information about the Stewards' seabird monitoring program, click here.

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