Eastern Black-Necked Garter Snake
Thamnophis cyrtopsis ocellatus

Non-venomous

Austin, Texas: April 24, 2004

Thanks to E. D., Austin, Texas, for these striking photos. This specimen of the eastern black-necked garter snake illustrates the range of variations often found in the markings of snakes within a given species. Instead of the typically well-defined double row of alternating black spots immediately below the spinal stripe, this snake has what appears to be a single row of black spots that are sometimes deltoid, other times rectangular, but at mid-body differentiate into a single instance of the typical alternating double row of round spots. The row of smaller black spots below the larger spots is present, but the small spots are irregular in shape.

Herpetologists are used to finding such variations and take them in stride, but amateurs are sometimes disconcerted by them. Try to keep in mind that just as humans, though a single species, show wide variations in hair, eye, and skin color, as well as in many other anatomical features, snakes also vary from one specimen to another. 

The dorsal scales of this snake are keeled, meaning they have a raised central longitudinal ridge. This feature is very obvious in the above photo. 

The dorsal scales of the head are unmarked and uniformly black or dark gray, as the photos above and below testify. A single scale forms the nose plate, shown in the photo above. 

The upper labial (lip) scales are marked with black at their vertical sutures and the scale below the eye is marked with black at its upper juncture with the eye. The last two labial scales at the end of the mouthline are bluish. The crescent found in the checkered garter snake is absent.

This species has a single anal plate (the ventral scale just forward of the vent) and the scales rearward of the vent are divided.

The distended belly is somewhat nodular, suggesting that the meal just swallowed was a large toad (this snake's favorite food). Note the belly markings of the ventral scales.