Diamond-backed Water Snake, juvenile (March 29, 2007)

 (Nerodia rhombifer rhombifer) Non-poisonous; temperamental; will bite if handled but a juvenile's teeth cannot break human skin (the adult bite is painful and draws blood but is otherwise inconsequential); beneficial

Photos courtesy of John R..; text by Jerry Cates

The markings found on this species consists of dark lateral patches of fairly regular shape (in the juvenile the usual regularity is sometimes violated, as in this specimen), offset by squarish spinal blotches (again, sometimes not so square, as here), with diagonal markings connecting the upper corners of the lateral patches to the spinal blotches.

The Nerodian head, particularly for the diamond-backed water snake, is distinctively rounded, in a semicircle that extends from the mouthline upward to the center of the head, then down the other side of the face.  The eyes are large with prominent circular pupils; the scale above each eye doesn't form a sharply defined brow-ridge, as in the cottonmouth, but merely accentuates the gentle, curved lines of the head.  The labial (lip)scales are pale yellow with dark vertical margins.

The head is large, with wide jaws that many presume to mean it is poisonous.  In fact, the snake is non-poisonous and, unless you tangle with a mature specimen and refuse to allow it to escape, harmless to humans.  The wide jaws enable the snake to grasp and swallow large fish, its favorite prey.

Body scales are keeled for this species, a fact that, in larger, mature specimens, makes the snake appear to have the hide of an alligator. The keels are the longitudinal mid-scale ridges running the length of each scale.  In this species, from 25-31 rows of scales are found at mid-body; in this specimen I count 13-14 rows from the lowest full scale visible to what I presume to be the mid-spine.  If the lowest visible scale abuts with a belly scale, this snake has from 26-28 mid-body scale rows.

The chin shields are the large scales in the middle of the lower jaw's ventral surface.  The two front chin shields normally abut directly along the midline, but the rear chin shields may be separated, in some species of water snakes, by one or two rows of smaller scales.  In this specimen of the diamond-backed water snake, no small scales intervene between the rear chin shields. Note how the upper lips extend out beyond the lower jaw, an anatomical feature common to the Nerodian water snakes.  The dark margins of the upper and lower labial scales are also characteristic of the genus.

Instead of the immaculate belly that many snakes have, the diamond-backed water snake's belly is marked with numerous crescent-shaped dark spots.  These are scattered in a semi-random pattern, with the larger spots near the lateral margins, and smaller spots in the middle of the belly.  The number and density of these spots varies, growing more numerous toward the tail.

To me, these markings appear similar to the cuneiform script found on late Mesopotamian clay tablets.  Cuneiform That association helps me remember that the diamond-backed water snake has these belly markings, because cuneiform employs wedge-shaped marks, two of which, joined together, form a diamond.

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