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February 2001

Avoiding Snakes: Nature’s Evil Twins

Some species look alike, but guess wrong and you could have a harmful mistake on your hands.

Also look at patterns. “The hourglass-shaped crossbands on a copperhead are narrow in the center of the back and wide along the sides,” says Beane. “On a water snake, they’re the opposite.”

The temperamental cottonmouth lives only in the South, in or near water. Unlike most other rattleless snakes, the cottonmouth stands its ground when disturbed, displaying its gaping, white mouth. The range of the snake includes much of the eastern half of the United States in almost any kind of wooded habitat, usually near water. Keep an eye out around rocky hillsides in particular.

Deadly Nuances

Some deadly and benign snakes look alike, but a few clues will distinguish them.

    Pit viper
  • Broad, flat, arrow-shaped head

  • Distinctly narrowed neck
  • Heavy-looking body
  • Facial pits
  • Vertical pupil

  • Elongated, oval-shaped head

  • Less narrowed neck
  • Proportionately slender body
  • No facial pits
  • Round pupil

Coral Snakes

For years, biologists believed the resemblance between the coral snake, North America’s most venomous reptile, and its harmless near-twins, the scarlet snake and scarlet king snake, was a classic case of mimicry. The impostors, scientists thought, adopted the coral’s colorful bands as a survival mechanism. Predators that learned the hard way to avoid coral snakes would avoid scarlets, too.

But since a coral snake’s bite invariably leads to death, there is no lesson to be learned, someone finally realized. So why, then, the uncanny similarity? “Nobody really knows,” says herpetologist Beane.

Fortunately, we do know how to tell the snakes apart (see below).

A mnemonic device to help you distinguish the two is, “Red touching yellow, dangerous fellow.” This rule of thumb holds true for both U.S. species of coral snake, the eastern and the Arizona or Sonoran. It doesn’t always apply to similar snakes south of the U.S. border, however. And in the Arizona coral’s Southwestern range, the harmless shovel-nose snake can also have adjacent red and yellow bands. To be safe, avoid them all.

Coral snakes live mostly underground or beneath natural objects. They surface to hunt only during the coolest times: evening for the Arizona species and early morning or late afternoon for the Eastern. Though furtive and rare, they possess venom more toxic than that of any other North American snake. Look before you reach under a rock or log.

Eastern coral snake:

Yellow and red bands are adjacent

Scarlet kingsnake:

Yellow and red bands don’t touch

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