Thamnophis proximus rubrilineatus - Red-striped Ribbon Snake
These diminutive snakes are regularly found around a home in Georgetown, Texas, on the banks of the San Gabriel River (Many thanks to Matt and Rachel, who invited me over to take these photos).
A small pond in the back yard contains tadpoles and small goldfish. These snakes feed on both, though their diets only infrequently include fish; they mostly eat frogs and toads, and rarely eat insects , lizards, or other snakes. Their chief prey is the cricket frog, a common anuran found year-round almost everywhere in shallow, freshwater environments. They are not venomous, and although they will nip if handled roughly their teeth are unable to inflict serious injury.
The dorsal plates on the head of this snake are broad and few, typical of the Colubrid Family of snakes. Notice the pair of white spots on the top of the head which, in this specimen, are joined so closely together that they appear as a single spot. In others the spots may be more obviously separated. The spinal stripe begins just behind the head and is initially pale in color. In this specimen the stripe is orange instead of red, a coloration that is uncommon.
Notice the pale vertical bar directly in front of the eye, which marks the margin of the singular scale adjacent to the eye. This scale is divided in the garter snake. Note also that the lip scales are uniformly cream colored without any other conspicuous markings. This latter feature distinguishes ribbon snakes from their cousins, the garter snakes, which have conspicuous markings on their labial scales. Texas has four subspecies of ribbon snakes, all of whom are races of a single species, differing only in coloration. In the photos above and below the pale lateral stripe that runs the length of the body can be seen. This stripe is always on scale rows 3 and 4 above the belly. The dorsal scales are heavily keeled lengthwise and generally occur in 19 mid-body rows.
The anal scale is single, and ventral scales beyond the vent are divided. Ventral scales are unmarked. The last few inches of the long tail of this species are easily discarded by the snake as a defense mechanism. Researchers report that 20% or more of the ribbon snakes found in the wild have already lost their distal tails. A captured ribbon snake may discharge a foul-smelling fecal material from its vent, and emit an odorous liquid from its scent glands, as a defense when captured.
The keels (ridges) of the dorsal scales are readily apparent in the photo below. The red spinal stripe and the pale lateral stripes serve as defensive devices. The snake moves with such stealth that, if only a portion of the body is seen, a predator will think the snake is not moving when it is actually speeding away. Only when the stripes suddenly narrow down at the tip of the tail does the fact that the snake is on the move become clear. By then, however, it is often too late.
The red-striped ribbon snake is a good swimmer, and typically retreats by jumping into the water and swimming away at the first sign of danger. Note that as this snake swims its body is entirely submerged. When it pauses in the water to rest, the body remains submerged and sinks even lower. This is characteristic of non-poisonous water snakes, all of whom tend to swim with their bodies submerged. The venomous western cottonmouth (known to many as the poisonous water moccasin), on the other hand, swims with its spine at the surface and, when it pauses in the water, the body floats. An easy way to remember the difference between the way the cottonmouth and non-poisonous water snakes swim is that cotton floats.