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Saturday, May 23, 2015

Munching at Miwok

Do you recognize this animal?  The picture above is a head-on close-up.

Here's a view from the side (a different individual):

Note the two rolled rhinophores (sense organs) sticking up, and the two flap-like oral tentacles extending forward.  The overall coloration is also distinctive blotches of red, brown, green and gold...and a network of dark lines (reminiscent of the crackle of raku pottery!).

Here's an entire animal viewed from the side:

This is a California Sea Hare (Aplysia californica).  We had heard that some had been observed at Miwok Beach (along the Sonoma Coast just north of Bodega Bay), so we stopped there this morning to take a look.

California Sea Hares are rare in northern California.  It's likely their presence here this year is due to the warmer water temperatures during the past year.

Although it's hard to tell from the pictures, they're quite large!  The maximum recorded size is ~75 cm (30 inches) long, and up to 15 lbs (7 kg).  Most are smaller, but still substantial.  The individuals we documented today were ~20-25 cm long.  Here's a picture with my boot for scale (this sea hare had been stranded out of water at low tide, but was just waiting for the tide to return):

Why are they called sea hares?  Well, if you return to the first picture of this post, you might be able to see a resemblance between this snail and a hare because of the way the rhinophores look like the tall ears of a hare.  And similar to rabbits, sea hares are herbivores in this case, grazing on a variety of seaweeds and sometimes seagrass.  Also, although it's probably not related to their name, sea hares move fairly fast relative to other snails.  [If you're wondering, sea hares are gastropods a group of molluscs that includes snails, limpets, nudibranchs, and sea hares.]

There were at least 50, and perhaps as many as 100 or so, California Sea Hares at Miwok Beach today.  It's not a species we see in this area very often, so if you find them this year, I'd love to hear about it!

P.S.  I've heard of reports of California Sea Hares in Tomales Bay this year, but I'm not sure of the exact locations.


Emily said...

whoa, 50-100 at Miwok Beach?! I have never seen more than ~6 small ones intertidally in San Diego and that was in an estuary. The most I have ever seen in the rocky intertidal at one site is 3 large ones.

Leth Benz said...


Serena Caplins said...

Hi Jackie! I thought I had seen you post about a lot of sea hares in northern California coast recently. I wanted to tell you, we went out to Coleman beach on Friday (7/3/15) and saw soooo many sea hares. I counted >40 while I was casually walking along a short stretch of the coast. There were many many more. It was great to see them! Do you think these are part of the same group that you saw in May? Or are they a second wave?

Jackie Sones said...

Hi, Serena! How large were the sea hares that you observed? If they were large, I'd have a tendency to think they were part of the same group that we saw in late May. But if they were small, then perhaps another wave has arrived. Thanks for letting us know about your observation!

Serena Caplins said...

They were quite large, around 15-20 cm, maybe bigger.