Eastern Black-Necked Garter Snake
Thamnophis cyrtopsis ocellatus

Austin, Texas (Wells Branch area): July 27, 2004

Thanks to Mark T., Austin, Texas, for these beautiful photographs. He is obviously an accomplished photographer with a good camera. This specimen has a full belly, probably a toad it has recently swallowed. 

Mark noted this snake was somewhat lethargic, which could be explained by its recent meal and the fact that the toxins in the toad have a powerful effect on the snake's body. A wide range of toxic substances are found in the toad's skin and parotid glands, including cardioactive agents, catecholamines, indolealkylamines and non-cardiac sterols. Not many species of snakes are able to consume toads without suffering fatal consequences from these toxins. Specialized adrenal glands are required.

This species of snake is most often confused with the red-striped ribbon snake (Thamnophis proximus rubrilineatus) which, at maturity, is much smaller. An easy way to distinguish between the ribbon snakes and garter snakes in general is to look at the snake's labial (lip) scales. Ribbon snakes have pale labial scales without markings. Garter snakes have prominent black markings on these scales, as shown in the photo below (an enlargement of the head in the photo above). 

The markings on the body of the black-necked garter snake consist of dark spots that form, at the neck, a large, black blotch at the back of the head followed by a single row of large spots above another row of smaller spots; by mid-body, the single row of large spots has become two rows of large spots (with a third row of smaller spots below). The two rows of large spots alternate and touch in such a way that they give a wavy appearance. The smaller spots, at the lowest portion of the snake's side, usually don't touch each other or the larger spots above them.

Body markings on the eastern black-necked garter snake immediately behind its neck and extending to as much as a third of its length consist of a single row of large dark spots that usually don't touch, above a row of smaller black spots.