Mud's eye view: to understand the world of the fiddler crab, ecologists peer through a lens that renders a landscape as a doughnut-shaped panorama

Natural History, April, 2004 by Douglas Fox

Hemmi was not at all surprised. A dummy raised above the ground, after all, appears closer to the crab's visual horizon; for the crab, that means it's farther away and less threatening. Of course, this run was still just the first test of the hypothesis. Other factors might have led to the same result: maybe the crab was distracted by a particularly delectable glob of mud. To justify his interpretation, Hemmi will need to analyze hundreds of runs with many different crabs. If he's correct, though, the crab's behavior is a potent indicator of how simple it can be to do trigonometry without the services of a mammalian brain.

As Hemmi and I fell silent beneath the vertical noon sun, the miniature dramas of Crabworld unfolded before us. There was chasing, eating, fighting, and mating, as well as vigilant watching and waiting. Each crab spied the world 360 degrees around for any threat, opportunity, or momentary advantage over its neighbor.

This flat cityscape in the mud, this crowded, competitive space, is their domain. For Hemmi and I, who stare down on it like gods from Mount Olympus, it's a difficult world to understand. But once we see it, at last, through the crabs' eyes, we have a much better chance of understanding what makes these little creatures tick.

Douglas Fox is a freelance science writer based in San Francisco. His work has also appeared in New Scientist, Discover, Scientific American, and U.S. News and World Report.