POSTED 18 JULY 2002

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Pray for prey

Photos by Lisa Ventre and Bruce Jayne, University of Cincinnati.

Dear MisMannerz:
I've grown disgusted at a trendy eating style of some slithering friends. As you know, well-behaved snakes eat their meals whole. While swallowing an entire pig may cause an unsightly bulge in the snake for some weeks, it leaves no scraps on the linen, and there are no eating utensils to wash.

As you have stressed, consideration for your hostess is the essence of good manners. I'm writing to ask about Gerarda prevostiana, a snake that eats soft-shell crabs. (No quibble with the menu, although I would suggest some Worcestershire....)

Problem is, this legless lizard grabs the crabs in its hose-like body and proceeds to strip off the legs. Then, without the benefit of so much as a lobster fork, it swallows the parts, one by one.

You may not deem the unmannered methods of this serpent worth a second thought. After all, it's no bigger than your little finger and doesn't grow more than a foot long.

But I fear that the practice of tearing up meals before eating them may be -- if I can adopt a well-worn metaphor -- the tip of the iceberg.

The more I think about it, the crabbier I get.

Today, no other species of snake is known to habitually tear apart its food before swallowing. With your help, we can steer impressionable young snakes away from this unsightly and unsanitary method of mastication.

I am enclosing an article about this onerous practice.

(MisMannerz replies)
Dear Grossed Out in Geneva:
Thank you for your insightful inquiry. I was not aware that any snakes had chosen to abandon the time-tested "one-gulp, hold the chew" method.

As you know, I normally do not condone gulping. I, like other mannerists, prefer that food be cut into suitable pieces before mastication.

However, tradition is a wellspring of good manners, and what is customary is seldom hideous. The struggling of a bush pig being consumed by an anaconda is acceptable at a formal table if the meal is swallowed head-first.

Indeed, my preference for tradition causes the shock and dismay I feel about the current case. Imagine, a snake deconstructing its meal before eating it!

I reprint below the article you mention. Perhaps other snakes will be guided away from the disgusting practice of yanking apart dinner on the plate.

Snake eats with "knife and fork"
Well, not exactly. But a group of scientists has discovered that Gerarda prevostiana, a crab-eating snake from the Singapore region, seizes its prey in its folds and rips it apart.

Only then does it eat the parts.

The snake forms itself into a loop and uses the loop to hold and tear apart its prey. Arrows indicate remains of the crab.

Some other snakes eat crabs, and like all snakes, they can open their jaws amazingly wide. But as you can see from the photo, ripping up your food allows the snake to eat a real lunker of a crab.

It's all in the timing. Gerarda eats only crabs that are molting -- growing new shells to replace outgrown older ones. Molting crabs, AKA "soft-shells," are doubly vulnerable, says Bruce Jayne, who studies lizard locomotion and other reptilian goodies at the University of Cincinnati.

Not only do the crabs lack protection, but without the shell, their muscles cannot transfer their force to the ground. And no traction, no action, so to speak.

Hard sell on soft shell
The research grew from a comparison of Gerarda to a related species that was known to eat hard-shelled crabs. Jayne, together with Harold Voris of the Field Museum in Chicago, and Peter Ng of the National University of Singapore, finally learned to collect the secretive Gerarda, which lives in and on muddy seashores dominated by mangrove trees.

In the stomach, the researchers found bits of soft-shell crabs which, suspiciously, looked like they had been torn apart before dinner. Was this just an accident, or did it reflect a non-traditional dietary habit of Gerarda?

The answer came from infra-red videotapes taken by Jayne and colleagues. As you can see, the little snake not only broke the crab up -- it broke every rule of the snake-etiquette book.

Sign of the crab
Unlike its relative, Gerarda focuses on soft-shells. Indeed, it's so turned on by them that the researchers learned to coax captive snakes out of their burrows with water from a container holding newly molted crab. "It was amazing to see them quickly emerge from the burrow, with their tongue extended and moving very rapidly, appearing very agitated," says Jayne.

The snake Gerarda prevostiana and its maximum mouth opening. How can such a snake eat such a crab? By disassembling the crab first, that's how.

They were, in other words, asking "where's dinner?" "For these, and many other species of snake, olfactory cues are extremely important for locating prey," says Jayne, "and for determining the identity of prey."

In contrast, water from a container holding hard-shell crab produced "effectively no response," he adds.

While Gerarda does break the "one-gulp" paradigm for snakes, Jayne does not think many other species have been disassembling their prey all along yet somehow fooling scientists.

A few other snakes might take bites from their prey, says Jayne, but in general, the one-gulp method is well founded. "The paradigm arose for a good reason. It's very important to emphasize that in no way do we expect to find this in dozens of species. It's very interesting because it's such a departure from the generalized condition for snakes."

-- David Tenenbaum

BIBLIOGRAPHY
Snake Circumvents Constraints on Prey Size, Bruce Jayne et al, Nature, 11 July 2002, p. 143.

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