Sunday, July 10, 2011

They Fiddle While We (Sun)Burn

I love the ocean, and its inhabitants, more than is probably good for me—or for those around me, who often have to suffer through my disquisitions on the subjects. But last weekend, at least, it was just as well that I had such an excessive fondness for all things marine.

Last Saturday, when Annie and I were on Cape Cod, we took a long (3-miles each way) walk on a trail that led through salt-marshes, alongside sand dunes, and finally to a beach on Cape Cod Bay. This would have been lovely (and in many ways still was) if it hadn’t meant that we had to walk most of six miles on shifting sand in the full heat of the sun—on one of those miraculous Cape-Cod summer days where there’s not a cloud in the sky. (Did I mention that I didn’t have a hat?)

This could have been a Very Bad Vacation Experience, in spite of the beauty of the dunes and water and the gorgeous liquid music of the song sparrows—if it wasn’t for my inordinate enthusiasm for marine life.

[a very cool non-marine sighting:
look at how this grashopper (locust?)
blends in perfectly with the sand]

Because, you see, as we trudged through the buggy, exposed marsh, we saw the most amazing thing. –At first, as we began our walk, I noticed only a shadowy scurrying in the seagrass litter by our feet. I followed the motion and discovered a small crab (less than an inch long), which quickly disappeared into a burrow in the damp sand.

We soon discovered that the marshes were full of fiddler crabs (Uca pugnax), all scuttling among their burrows or wading into puddles of brackish water or waving their claws with great pomp.

[Notice how huge its left claw is compared
to its eentsy-weentsy right-hand one;
do fiddler crabs have Pincer Envy?]

This was thrilling for me, since I’ve seen the openings of their burrows many times—little holes in damp sand, surrounded by small balls of sand made by their excavations—but had never before seen the actual crabs, much less such a swarm of them. (This is their breeding season, and, as this excellent article on their ecology and behavior describes, the males gather in leks—big groups of show-offs—to compete for mates and see whose large claw is the biggest.)

Annie thought they were pretty cool, too. So, thanks to the distraction of a novel marsh-side sighting, we were able to enjoy what the walk did offer us and—mostly—dismiss what it didn’t (like restrooms or more than ten minutes of shade).

Thus I illustrate the value of an obsession with the sea.

P.S. If you want to know more about fiddler crabs—based on my reading, not much personal experience—please ask me in the comments, and I’ll tell you.

{A note: I do write all text and take all pictures. Please do not reproduce either without my permission.}


biobabbler said...

wow, how cool.
1. that is the best, briefest-while-still-accurate explanation of a lek I have ever read.

2. I have a friend who did work on fiddler crabs for his dissertation and one aspect that was genius was that he could only do field work during low tide. No 15 hour days in the field (like goofy chicks who study mice and ALL the vegetation they live in). Nope. Few hours here, few hours there, voila.

3. I love the species name, pugnax, as in pugnacious, as in: having a quarrelsome or combative nature : truculent (Merriam-Webster). =)

Fighty-McFight-Fight. =)

Olivia V. Ambrogio said...

Biobabbler: 1. thanks for that compliment!
2. Ah, but the tricky thing about only being able to do fieldwork (or in my case field collection as well) at low tide is that you *have* to do fieldwork at low tide, whether it means driving somewhere at dawn or working on experiments at sunset when the no-see-ums come out in force to eat your scalp or working in icy winds when you can't see through the foot of water and slice your hand open on a snail-shell (just an example). But I can see that studying mice *in* vegetation would be another good way to make one re-think career choices. :)

3. Yes, such a great name! Almost as good as the snails I used to study, whose latin name was Crepidula fornicata. (Supposedly for the architectural term "fornication," but since they lived in states of perpetual orgy, I have my doubts.)

biobabbler said...

Yes, true. =) I used to work with a marine biologist and when people complained that she wasn't always at her desk 8-5 (super easy to reach) I'd say "Well, when the tide is low at 1 in the morning, she's out there, and no one else is, so...." Poor thing. =) She's TOUGH, though.

Anca said...

Love the title, the photos, and the commentary. Now, WHY do they have such disproportionate claws? I'd think it'd make it harder to grab and feed, but, obviously, what do I know?

Olivia V. Ambrogio said...

It DOES make it harder for them to do things! And, in fact, only the males have an unusually enormous claw--the females' claws are both normal-sized. It's a mate-competition thing, and according to the article from Animal Diversity Web I linked to above, like many such traits, it has its costs: "The larger chelea [claw] is both an advantage and hindrance. In displays of aggression the male with the larger chelea is usually the victor, but the male with the larger claw is at a disadvantage in burrow construction and foraging."

Anca said...

Another example of "intelligent" design, no? Another example of the economic analogy failing when it comes to biology.

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