Texas Rat Snake, juvenile

 (Elaphe obsoleta lindheimeri) Non-venomous, Aggressive (bites), Beneficial--Found wrapped around an outdoor light fixture in Austin, Texas -- 8 Oct 2004

Photos courtesy of Richard D

The Texas rat snake is an equal-opportunity feeder, and doesn't discriminate much when presented with something suitable for eating.  It is common to find the species wrapped around joists under decks, including elevated decks on multi-story buildings, or around light fixtures--such as the one shown in the photos below.  The attraction, in such cases, is the large number of geckos that congregate in such places to feed on swarms of insects around the nocturnal light source. This particular specimen was a juvenile, only 12 inches long.

But how can we be sure this is a Texas rat snake?

OK, first things first.  The tail is long and tapered, ending in a point, so it isn't a rattlesnake. The spinal saddles exhibited by this specimen are not found on any of our poisonous snakes in Texas, so it isn't a cottonmouth, copperhead, or coral snake, either.  But saddles are common on a lot of other non-poisonous snakes, besides the Texas rat snake, so how can we be sure this isn't one of those?  The lateral blotches on the snake's side are more numerous than those commonly found on a mature Texas rat, but look a lot like those found on the bull snake (Pituophis catenifer sayi)... can we be sure of this specimen's identity? 

The first thing I looked at, after seeing the lateral blotches, was the marking of the tail.  A bull snake's saddles stop short of the tail, and are replaced by rings that are spaced as far apart as they are wide.  This snake has markings that appear to be saddles all the way to the tip, but although they could be rings, they are spaced too close together to be a bull snake.

The scales on this snake's body are generally smooth, too, though the scales near the spine appear to be mildly keeled.  The bull snake has strongly keeled scales except for those adjacent to the belly scales, while the Texas rat snake has smooth scales except those at the spine, which are weakly keeled. 

Counting the scales diagonally up the snake's body at midsection, starting at the belly and ending at what appears to be mid-spine, I find either 13 or 14 scales, depending on which row is counted.  The bull snake usually has 33 rows of scales at midbody (17-18 of which would be visible on this side of the body, spine to belly), while the Texas rat snake usually has 27 (13-14 of which would be visible on this side).  Again, this points toward the Texas rat, but it doesn't rule out the corn snake (Elaphe guttata guttata), which has the same number of scales at midbody, but which also has several rows keeled instead of the one or two rows found in the Texas rat.

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