Juvenile Texas Rat Snake
Elaphe obsoleta lindheimeri

Frisco, Texas -- October 2003

Thanks to S.M., Frisco, Texas, for sending in these photos

The gentleman who sent in the photos shown here found this snake near his front doorstep in October 2003. He was startled at the snake's aggressive nature, which suggested to him that it was a dangerous, venomous species. Since it was small, he was able to corral it in a small tub until a snake expert from the Collin County SPCA came out (the next day) to identify it and take it away. He was then told the snake was "a poisonous cottonmouth" which the SPCA would euthanize at their facility. 

So much for experts. This snake is a juvenile rat snake in the genus Elaphe. It is non-venomous but, as already noted, very aggressive. As an adult it will feed primarily on rats and mice and their young, and its ability to secure its food with regularity requires it to be somewhat pugnacious; rodents that aren't pursued with a vengeance get away or put up a fight that may injure the snake. Successful rat snakes take their prey down quickly and decisively, and that requires them to be mean and unfriendly. The same tendency tends to earn them respect from other beings, like dogs and humans, who prefer to turn tail and run rather than deal with this snake's unfriendly attitude. Most of the time that gives the snake time to escape. Sometimes, however, it results in the snake's demise at the end of a shovel, and ax, or a rifle.

Note the markings on the head of this snake (an enlargement of the head is shown below). A dark mask covers the eye and wraps around the head under the prominent skull ridge over the eyes. Further back on the dorsal surface of the cranium another dark marking encircles much of the top of the head, but is a lighter gray in its center, with three dark spots, two forward with one larger spot behind them. These cephalic markings will slowly disappear as the snake matures, leaving the head uniformly dark. Two other species of the same genus, the corn snake (Elaphe guttata guttata) and the Great Plains rat snake (Elaphe guttata emoryi), have similar markings on their heads that remain visible in mature specimens. These markings, however, differ from those shown on the specimen pictured here, in that the dark cranial mark is open at its forward edge, and forms two spear-points (which, sometimes, do come together but at a narrow margin that nearly separates), while the marking of the juvenile Texas rat snake is closed by a broad band across the cranium. 

The western cottonmouth (Agkistrodon piscivorous, the only species of cottonmouth native to Texas) lacks the prominent skull ridge found in the rat snakes. Instead, its head is uniformly flat, dorsally, from its neck to its nose. Juvenile western cottonmouths bear bold patterns that resemble copperheads. The lower lip scales have pronounced white horizontal pinstripes on the edges of the lower lip scales. Like juvenile copperheads, their tails are sulphur-yellow in color. In the adult western cottonmouth the dorsal surface of the head bears no unusual markings, but they have a conspicuous dark cheek stripe stretching from the eye backward to the end of the mouthline. This mask is edged in white and can be seen from a distance.

The saddle markings displayed on this Texas rat snake specimen's spine are not unique to any given species, but are found on the glossy snakes of the genus Arizona, the corn and rat snakes of the genus Elaphe, the bull snake and the Louisiana pine snake of the genus Pituophis, and even the Texas long-nosed snake of the genus Rhinocheilus. Such markings are not found on the western cottonmouth, although the latter may have a series of poorly-defined crossbands. For a more complete discussion on snake markings, along with photos showing markings found on various snake species, click here.