Rat Snake (Elaphe spp.)

Lumberton, TX 30 Jun 2009, Meredith C.

In memory of Marc D. McCullough (1975-2008), and dedicated to his daughters, Madelyn and Abigail, whom he taught to love God's earth and its creatures.

Merideth wrote: "We live in southeast Texas, in Lumberton (Hardin County, just north of Beaumont). My husband eyed this snake on one of the lines running from our house to a utility pole in the neighbor's yard. We hadn't had any rain in 2-3 weeks, but got a welcome rain shower that afternoon. Later that night, our little friend appeared. Our families are decently educated in the snake department, but we're not sure what we have here. Can you help identify it for us?"

I hastily wrote back that  this appeared to be a Texas rat snake, judging from a cursory count of the number of spinal saddles and the essentially unmarked dorsal head (but see the comments provided below). Then I asked if the snake had lost its grip on the wire on its own, or if someone had jiggled the wire to produce the acrobatics. She answered: "My husband tried to knock it down with a broom so he could check it out on the ground. He hit it four times and it never fell. You can see how it has its tail wrapped around the wire to secure itself from falling. By the way, my 3 year-old daughter is a HUGE snake fan! My husband, on the other hand, is terrified of snakes, but I don't hate them as much as I hate spiders. Which reminds me, I saw my first black widow spider EVER this past Sunday; I got a pic if you are interested." Of course, I was interested, and she sent the black widow spider photos in a subsequent message.

Meredith and I exchanged a number of messages. In the process, I learned more about her family and especially about her brother Marc. [Marc died last year--a year and a day prior to the discovery of this snake--in a head-on collision with a vehicle driven by a youthful driver who lost control and crossed into Marc's lane. Marc's wife, Tonya, and his two daughters were in the car with him, and were also injured but are mending. Marc was a lover of nature and its creatures, and taught his daughters to follow in his footsteps. Perhaps, one of these days, bugsinthenews will be honored by the receipt of a few encounter reports and photographs from one or more of these young ladies.]

The photograph below is of the rat snake featured on this page after it met its end. Meredith's husband was not sure if it was dangerous or not, so he did what any normal, red-blooded Texan would do under similar circumstances. As a result, a perfectly fine rat snake is no more. My advice is that you not mourn this animal's passing; many of its kind are killed each year entirely unheralded, but this one will be different. We shall put its demise to good use to educate ourselves on the best ways to tell if a snake is venomous or not. We will then proceed to point out the salient features that seem to distinguish this specimen as a rat snake in the genus Elaphe, and that separate it from similar serpents found in Texas.

Please note that, without having the actual specimen in hand, so that positively accurate counts of blotches, mid-body scales, or analyses of the scalation of the head, tail, and vent can be done, our "identification" of this snake cannot be assured. Many genre have similar markings, and the most likely genus, Elaphe, is entirely too varied (and, may I say, presently too confused in terms of the extant contradictory scientific literature) to permit such an assurance from the limited photographic evidence provided here. What we can say, with absolute assurance, is that this is a non-venomous species (none of our venomous North American serpents have these markings), and that--from all the evidence available to us--it most likely falls within the genus Elaphe.

Note first that this snake has a series of prominent, dark blotches, roughly shaped like saddles that are longer than they are wide, and that are positioned dorsally, along the spine from neck to tail. If you count these blotches, they appear to number about 42-44 or so (possibly a few more or a few less). In the literature, we are told that the spinal blotches of the Texas rat snake number from 25-38 (some, e.g., Werler & Dixon, place the upper number at 37). In other words, at least based on the definitions found in certain of the authoritative literature, this seems not to be a Texas rat snake, as I first thought.

The Texas rat snake is said to readily interbreed with other rat snakes, most notably Elaphe obsoleta spiloides, though such interbreeding has only been reported several hundred miles north of where this snake was found. Another species, Slowinski's corn snake (Elaphe slowinkskii), [named after Dr. Joseph Bruno Slowinski (1962-2001), who died on September 12, 2001, after being bitten the previous day--yes, the infamous 9/11/2001--by a multi-banded krait (Bungarus multicinctus) while on an expedition to conduct a comprehensive survey of the herpetofauna of the Union of Myanmar (today's official name for the nation previously known as Burma)] is a possible contender.

It happens that the Texas rat snake and Slowinski's corn snake have overlapping ranges, and both are found in the region around Lumberton. Is Slowinski's corn snake similar to what we see here? That's a good question, and for the moment I don't have a good answer, as the literature is inconclusive. Herpetology is, as most of our biological endeavors today, an inexact science. Nowhere is this more true than in taxonomy. It is inevitable, given the present explosion in DNA analysis and the resultant overturning of many of our previous notions about the way various species are related to one another, that we find our schemes of classification in disarray.

And disarray is, indeed, what we find. In a 2001 paper authored by Frank Burbrink, he describes the various subspecies embraced by the species Elaphe guttata. The nominate form, E. guttata guttata, as described by Burbrink in this paper, is curiously similar to Werler & Dixon's 2000 description of the Texas rat snake (E. obsoleta lindheimeri), especially with regard to the number of spinal blotches (25-38) and its typical background coloration (orange, reddish-brown or gray). In this regard, Burbrink agrees with Klaus-Dieter Schulz, in his 1996 "Monograph of the Colubrid Snakes in the Genus Elaphe Fitzinger" (pg. 284). Werler & Dixon, in their acclaimed book "Texas Snakes" (pg. 108), put the number of spinal blotches for E. guttata guttata at 44-59, averaging 51; an accompanying photograph of a specimen of that species displays features that agree with the textual description. At least the material in Werler & Dixon agrees internally, even if it fails to agree with the material in the writings of other herpetologists, all of whom are recognized authorities in the field. This disparity, fom one source to another, is frustrating, but science is often like that.

In the meantime, let us concentrate on Meredith's specimen and glean as much from that as we can. A close up of the head and forward body is shown below. Note the presence of light gray belly markings that include from two to three belly scales at once. We cannot tell, from this photo, if the mark extends completely across the belly, or stops somewhere in between. Their regularity seems to contrast with the signature mark of the corn snake, which is more random and varied, as is seen with the differently colored kernels on a cob of maize, from which the corn snake derives its common name:

In the photo below, we see an enlargement of the right-hand portion of the photo above. Although this is not the mid-body of this snake, it is as close as we can get, given the photograph Meredith sent along. She did a great job, but of course there are never enough of all the various anatomical features to do everything one would like to do, so we will do the best we can with what we have. I count fifteen scales on this side, from the belly to what appears to be the middle of the spine. Assuming the count on the rest of the body, to the belly on the other side, would be 14 additional scales, the total "mid-body" count (which does not include the belly scale) would be 29. Both the Texas rat snake, along with Baird's rat snake (which is not found near Lumberton) have but 27 mid-body scales, while the three subspecies of corn snakes (Elaphe guttata guttata, E. g. emoryi, and E. g. meahllmorum) found in Texas have either 27 or (rarely, according to several sources) 29. It is impossible to tell for certain that this specimen has 29 mid-body scales, but the likelihood seems rather good, which suggests this is a corn snake--possibly even Slowinski's corn snake--and points away from its identification as a Texas rat snake. 

Now, about the head. I had to take advantage of image enhancement software to bring out subtle features not otherwise immediately obvious in Meredith's original photograph. The result shows that the head is not exactly unmarked, as it seemed at first glance, but has signs of a spear-point-like marking on each side of the dorsal head. Yet, these markings are not immediately obvious, as they are in most of the literature on the corn snakes. Several other photographs, of similar snakes taken in the same general geographic region in 2009, have been sent to me by other contributors over the past few months. I remember seeing similar head patterns to this one, and it is likely the same species is involved. As I process these, perhaps we will learn more about these snakes.

A close up of the lateral head is shown below. This portrays the upper and lower labials quite well. As would be expected with the genus Elaphe, the upper labials number 8; the lower labials, however, seem to number 12.

Hopefully this material heightened your interest in the subject of herpetology. You surely noticed that much is yet unknown about Texas snakes. Rather than discouraging you, that fact should make you want more than ever to get involved in helping us fill in the gaps and make strides forward in our understanding and knowledge. The field is still wide open, quite contrary to what you may have previously believed. If you happen across a snake in North America, please photograph your discovery and send me copies of your photos. If you find snake skins, left behind by snakes when they shed, collect them, record where and when they were found, and send them to me for analysis. Whenever possible, every inquiry is answered immediately--I try to answer every email inquiry within minutes of reading it, and every telephone inquiry is answered on the spot, as all who call will testify.

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