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Nature Watch: Everything from Armadillos to Zebra Butterflies

At Home in the Sand

Sand: It comes in a remarkable array of colors and textures and decorates the world's deserts, riverbanks, and beaches in dunes and flat plains. Children like to sculpt it into castles and cover themselves with it, while adults prefer its wet kiss on their bare feet, the firm cushion it provides after a swim in the ocean. But humans are not the only creatures with an affinity for sand.

As noted, sand comes in a seemingly endless variety of colors. Hawaii alone has beaches with black sand, white sand, green sand, red sand, and black-and-white sand. And for every hue sand takes, there are animals perfectly adapted to it.

Basically there are two types of sand creatures, those that live on sand and those that live under it. They vary in size and concentration, from huge solitary sharks to microscopic organisms massed together by the millions.

In the American Southwest, many kinds of horned lizards and rattlesnakes, including the Sidewinder, have exteriors that match the sandy environments in which they live. Often the resemblance is so close that it's all but impossible to distinguish the animal from its habitat. The same is true of desert and seaside grasshoppers and tiger beetles, two superbly camouflaged insect groups.

Birds, too, can blend in perfectly with sand. In fact, the Piping Plover, now a federally endangered species of shorebird, has suffered because of its coloration. Its feathers so precisely echo the color of the white sand it chooses for its nesting site that sometimes the young, which instinctively crouch down low to the sand when danger threatens, are killed by drivers of off-road vehicles who cannot see the birds.

In shallow ocean waters white shrimp and flounders, animals that live on the sandy ocean bottom, also blend in so well as to be virtually invisible. Usually, we see them only as they scurry away from our footfalls.

Of course, for every creature living on the sand another lives buried beneath sand. Unlike their above-ground counterparts, though, these hidden animals don't need to be cryptically colored. The sand provides protection from many predators. Plus, sand is relatively easy to move around in and stays at more or less a constant temperature for long periods of time.

Some of the better known sand-loving animals are the different clam species that dig themselves into the bottoms of coastal lagoons and freshwater rivers and ponds. The tapered shell, pulled forward by the powerful foot of the clam, lets the mollusk move through sand at a surprisingly rapid rate. Razor clams have been known to dig through sand faster than people.

 

 

 

 

 

2007 eNature.com