Salt Marsh Part 2: A Snail Tale

(Continued from this post.)  Peer into the vegetation in the salt marsh and you’ll quickly realize that the whole place is absolutely crawling with snails.

(Note also the salt crystals encrusting the grass – it’s not called the salt marsh for nothing!)

These snails are Melampus bidentatus, the common marsh snail, an air-breathing snail that munches on decaying marsh grass.  When the high tide floods the marsh, they crawl up to the tops of the stalks of grass to stay above the water level.  They seem to “know” when the tide is coming in, but no one really understands how.

We sometimes do an activity with the kids we call “snail charming,” in which you press a snail against your throat and hum; the idea is that the vibrations coax it to open up and peer out of its shell.  I’ve found that simply holding a snail still in your had works just as well, but it’s fun to watch a group of middle school students humming in harmony while holding little snail shells pressed against their vocal cords!

I think they’re cure.  Then again, I think snakes are cuddly.

Supermoon = Supertide!

Everyone has been talking about the “supermoon” last night, but just in case you’ve been living under a rock, let me break it down for you: last night’s full moon happened to coincide with perigee, the point during the moon’s monthly orbit at which it’s closest to Earth.  This happens fairly infrequently, and when it does the full moon looks a little larger than normal.  (Contrary to what you might have heard, however, there is no evidence linking so-called supermoons with major natural disasters like what happened in Japan last week.)  Wikipedia has a good article on the subject, including an image comparing the size of last night’s moon with that of a more typical full moon; it’s not really that much bigger, and I think most people who were astounded by the huge moon last night probably just aren’t in the habit of watching the full moon rise on a regular basis.  While the moon did look impressively big and orange last night, it wasn’t particularly bigger or oranger than other full moons I’ve seen when they’re just rising above the horizon.

However, the real story here… is the supertide.

The most extreme tides every month, called spring tides, happen immediately following the new moon and full moon, when the Earth, moon, and sun are all in a line.  I wrote about spring and neap tides previously in this post.  When this happens at the same time as perigee, like it did today, the effect is even greater and the tides become truly crazy.  I didn’t see the beach at high tide this morning, but I was back on the marsh side of the island and was shocked to see practically the entire marsh flooded, the tidal creeks about to bust out of their banks.  So six hours later I made sure to hustle down to the beach to see the opposite end of the spectrum, the ridiculously low tide, exposing areas of sea floor that probably hadn’t been above water for a long time.

The water’s edge revealed supersaturated sand that sucked at my feet as I tried to walk, interspersed with deposits of rich black mud.  And in the sand were some interesting critters, like these sea squirts, which pulsed gently as I watched (my hand is for scale)…

…and this odd lump of mostly-buried material.  Little currents coming out of it suggested something living, but what, and where?  In it?  Under it?  What was this thing?

Finally I gently grasped its edge and flipped it over, then jumped back in shock.  It was an enormous whelk, alive and wiggling, its shell so encrusted that I hadn’t even recognized its shape!

I was going to take more photos, including some wide shots of the whole beach to try to give you a better sense of the craziness of the low tide, but my camera chose this moment to jam up and stop working.  And of course, it was after my camera went bust that I found the dead dolphin.  TO BE CONTINUED…

Teeny Tiny Itty Bitty Whelk

I recently posted this photo of a whelk egg case:

Sometimes if you’re lucky you can rip open the casings and find tiny unhatched whelk babies.  Usually when I try this I just find them to be filled with sand, but today I got lucky and snapped what may be my new favorite photo.

All together now: awwwwwwww!  Incidentally, it is possible to tell which type of whelk the egg case is from by the case’s shape, but I can never remember which is which.  Knobbed whelks are what’s most common here, so let’s go with that.

Snake Bones and Snail Snot

This spiraling structure is a fairly common find on our beach.

Kids see this and immediately recognize it: the skeleton of an exotic sea snake!  These round rubbery things with the frilly edges, though…

…these are harder to identify.  If a kid picks one up and asks me what it is, I’ll have them carry it for a bit so I can talk to the whole group about it the next time we stop.

The first photo, in case you haven’t guessed, actually has nothing to do with snakes.  It’s the egg case of a whelk, which some people apparently call a “mermaid’s necklace.”  The second one is the egg mass of a moon snail, which is commonly referred to as a “sand collar,” because whole ones resemble old-fashioned detachable shirt collars.  To make a sand collar, the female moon snail cements grains of sand together with mucous, embedding her tiny eggs in the matrix.  Which means that, after making the kid who picked it up carry it for several minutes, I get to wind up my explanation with “…so basically you’re holding snail snot” and see the look on their face.

Isn’t outdoor education grand?

Gray

This afternoon, after I got off work, I put on three extra layers of clothing and my wool hat and braved the cold, wind, and rain to walk on the beach.

Yes, I swear my camera was not set to black and white when I took that photo – it really was a grayscale landscape.  The advantage to going on such a dreary day was that I had the beach all to myself, at a time when the unsettled weather meant that the waves had been dredging all sorts of pretty things up onto the shore.

At the south end of the island, I was surprised and delighted to spot several Laughing Gulls whose black hoods had almost completely grown back in – a sure sign of spring? – plus there were about half a dozen skimmers around, which I hadn’t seen for a while.

By far the best find, however, was a knobbed whelk shell as long as my hand, the biggest once I’ve ever come across.  When I spotted it it was mostly buried in the sand, and I couldn’t believe my luck when I pulled it out and discovered that it was intact, empty and whole and perfect.

I’m not a big shell collector most of the time.  What would I do with boxes full of shells?  Better to leave them for the hermit crabs, who can put them to good use.  But this one, heavy though it was, absolutely had to come home with me.  When I flipped it over…

…its rough gray outside revealed an impossibly brilliant red-orange interior, one warm spot of color on the grayscale beach.

Moon Snail Mayhem

One must-discuss mollusk (say that ten times fast) during every beach class I teach is the moon snail (family Naticidae).  What middle school student – heck, what person – wouldn’t be fascinated by an animal that uses its tongue to drill holes in the shells of other animals and eat them alive?  And sometimes practices cannibalism?  The life history of this critter, identified by its round, smooth, spiral shell,  is guaranteed to earn wide eyes and “Wow!”s from any group of sixth-graders.

The telltale sign that a moon snail has been up to its mischief is a clam shell with a small round beveled hole drilled through its end.

When I was a kid, I found a shell like this and strung it on a length of red yarn to turn it into a necklace.  Never did I pause to wonder how the heck the hole got there.  When I finally learned about moon snail predation a couple months ago it was like I was a cartoon character with a light bulb going off above my head.  Aha!

Moon snails, you see, have a long, minutely toothed, tongue-like appendage called a radula, which (in combination with acid secretions) they use to drill a hole through the shell of their bivalve prey.  Then they insert their proboscis into the hole to consume the fleshy animal inside.  Alive.  Whoa!

Better still, they don’t limit their ravenous rampages to clams.  No, big moon snails are quite happy to eat small moon snails.  Finding a little moon snail shell with the telltale hole during beach class is a guaranteed crowd-pleaser.

Cannibalism!  Acid secretions!  Drilling holes with its tongue!  It’s like a horror movie monster, washed up right here on our beach.  Who knew there was so much drama in the world of seashells?

Sketchbook

When I started this job, I bought a little notebook of unlined paper to double as journal and sketchbook.  I can’t claim to be much of an artist; the only time in the past I’ve done anything resembling nature sketching was when I took ornithology in college and used drawings to record data on, say, feather maintenance behavior, and those were basically the bird equivalents of stick figures.

Yeah… obviously birds that are on the ground sitting relatively still are easier to draw than birds in flight.

Inanimate objects are much easier.