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DFW Herpetological Society - Herp of the Month
September 2003


The DFW Herpetological Society is a group with a mission - to promote understanding, appreciation and conservation of reptiles and amphibians, and to encourage respect for their habitats.

If you want to learn about native species and recognize venomous snakes, this is the group for you!  Interested in observing and photographing reptiles and amphibians in the wild?  DFW Herpetological Society members enjoy field trips to local destinations as well as weekend-long expeditions to locations such as the Hill Country and Trans Pecos.

Anyone interested in herps is welcome at their meetings!  Meetings are held the 3rd Saturday of the month at 7:00pm, in the UTA Life Sciences Building, Room 119.  Check out www.dfwherp.org to learn about this great group!


This article is reprinted with permission of the DFW Herpetological Society.
Author Michael Smith, Editor  Cross Timbers Herpetologist


Elaphe guttata guttata

Great Plains Rat Snake

It is tempting to say that this article is about the “DOR snake” since so many of the ones I see are “dead on road,” in field herping parlance. A sampling from my field notes shows that I’ve seen Great Plains rat snakes in Tarrant, Parker, Wise, Palo Pinto, Erath, Coryell, and Kerr counties, mostly in April and May but a couple in June and also in August and September. I’ve found them at 9:09 or 9:20pm, or around 11:00pm, or just after midnight. And, on the roads, all but one have been DOR. Last August 11th, at 8:40pm, just as it was getting dark, the Benbrook-Aledo Road yielded up one more Great Plains rat snake. I had passed an oncoming pickup truck a half-mile back, and then I came upon this small snake slowly moving across the road. When I picked it up, I thought about how long it had been since I’d seen one alive on the road, and then I noticed that it’s struggles were not well coordinated and it had a tinge of blood under the right eye cap. I took it along to see if the injuries would prove to be fatal; if it died, at least it could add to the scientific collection at UTA. The snake seems to be doing well, and is pictured in this article.

A note on taxonomy: this is a subspecies of the corn snake (Elaphe guttata guttata). Since some biologists do not place much importance on subspecies, the Great Plains rat snake is closely related or might even be considered a western race of the corn snake. Recently, some herpetologists have considered that the Elaphe guttata in east Texas is the corn snake subspecies, while those in south Texas below the Balcones Escarpment are “southwestern rat snakes” (Elaphe guttata meahllmorum). That leaves the rest of Elaphe guttata in north Texas, the hill country, and west Texas as Great Plains rat snakes (E. g. emoryi). The subspecies meahllmorum and emoryi look very similar, but differ in such characteristics as number of dorsal blotches and number of belly scales. It is worth remembering that you cannot straddle a line and say that your left leg is in emoryi country while the right is in the range of guttata. The subspecies intergrade (breed together, producing animals with some characteristics of each) where their ranges touch.

In Wright & Wright’s Handbook of snakes, the common name at the time was “Emory’s pilot snake” or “Emory’s rat snake” (still in some use today). Other common names included “Spotted mouse snake.” And at that time, this snake was given species status: Elaphe emoryi.


Description

This is another brown-blotched snake, sharing that general pattern with a broad variety of the snakes of the prairies and open woods. Among the most important distinguishing marks is the “spear point” pattern on the top of the head. Viewed from the top, these snakes (all the E. guttata subspecies) have two dark markings that come together on the crown of the head, pointing forward. There is also a dark band across the snout that angles back through the eyes and diagonally to the jawline. Great Plains rat snakes have relatively large eyes as well.

The dorsal blotches may be a bit longer on north Texas specimens, while E. g. emoryi in west Texas may have more narrow blotches and the snake may be somewhat paler. Those blotches, down the body and tail, average 67 — more than those of the corn snake. Blotches may be a rich brown or may be more gray or slightly olive-colored. Underneath, The Great Plains rat snake has a white belly with black markings, but they tend not to be so bold as the black checkerboard of the corn snake’s belly. Under the tail, the dark markings fuse into two stripes toward the end, just like the corn snake. Scales are weakly keeled, and the anal plate is divided. This helps differentiate it from the similarly-marked prairie kingsnake which has smooth scales, a single anal plate, and relatively smaller eyes and head than the Great Plains rat snake. Young Texas rat snakes have a band across the snout and a somewhat similar blotched appearance, but they do not have the spearpoint design on the head or the stripes underneath the tail.

Great Plains rat snakes tend to be about 24 to 48 inches long. Werler & Dixon (2000) show the record length as 72 inches, while Tennant (1998) shows it to be just over 60 inches.


Habitat

This is a snake that can live in a variety of habitats, from prairie and open woodland to rocky hillsides and even caves (where it reportedly feeds on Mexican free-tailed bats). In our area I have most often seen them in remnant or disturbed prairie or old fields near barns and discarded materials that provide ground cover. Ecologist Jim Eidson, at the Nature Conservancy’s Clymer Meadow in north Texas, cites it as a common species there. Herpers commonly find Great Plains rat snakes while herping the Trans Pecos and Big Bend, and they are found throughout the hill country.

From Texas, the range of the Great Plains rat snake extends down into Mexico, westward into New Mexico, up through Oklahoma and much of Kansas, and into parts of Missouri and Arkansas. It is also found in a disjunct area of western Colorado and adjacent Utah.


Food

Mice and rats appear to be the primary prey items, but these snakes will also take ground-nesting birds and their young. As noted above, these snakes will eat bats, and they have been reported living inside caves where they helped themselves to the free-tailed bats found there. In captivity, these snakes do well on a rodent diet just as one would feed a corn snake.


Activity and Behavior

Depending on the local climate, Great Plains rat snakes will emerge from hibernation by March. At the end of their activity season, they may enter burrows, crevices or caves for hibernation by October or November (again depending on local temperatures). They are active at night, and tend to be secretive. Thus, they are found either by turning boards, rocks, or other ground cover, or by road-cruising at night. When discovered, they may rattle their tails and might offer to bite if picked up. However, it is very common for a Great Plains rat snake not to bite, even when initially picked up in the wild. In captivity they have an easygoing temperament similar to the corn snake.


Abundance

Field notes and observations of naturalists and field herpers indicate that this is a common snake. In places it is not encountered as often as the less-secretive snakes, but in suitable habitat areas it is generally considered abundant.


Reproduction

Mating occurs soon after leaving hibernation, and females deposit from 3 to 27 eggs (Werler & Dixon, 2000) in June or July. Like other Elaphe guttata, the Great Plains rat snake’s eggs are coated with an adhesive substance that tends to lock the eggs together in an inseparable mass. The approximately 10 to 15 inch babies hatch in August and September.


References and Further Reading



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