Geographic range: Nearctic - Neotropical: This species inhabits the Sierra Madre Occidental and the Central Plateau from ec. Sonora and wc. Chihuahua south through Durango, sw. Coahuila, Zacatecas, Aguascalientes, Nayarit, Jalisco, Michoacán, sw. San Luis Potosí, Guanajuato, Querétaro, México and D.F.

Note on taxonomy: The populations in Sonora and Chihuahua are Thamnophis melanogaster chihuahuensis
From Durango and Coahuila south to Michoacán and Guanajuato are Thamonophis melanogaster canescens.
In the "Valley of Mexico" including D.F., portions of the México, Queretaro and Michoacán occurs Thamnophis melanogaster melanogaster. In the Valley of Toluca occurs Thamnophis melanogaster linearis.

Physical characteristics: A medium sized, slightly robust snake (40 to 50 cm). Both sexes are of the same size. Body color ranges from brown to gray. Lighter (gray or yellow) longitudinal lines might be present (usually one vertebral and one lateral on each side of the body), but uniform color individuals are common. Scales of the dorsal region are strongly keeled. Lateral scales are smooth. Ventral region of the body is dark gray and a notable longitudinal patch covering half of body and tail length is present.

Food habits:
57% - Fish
20 % - Leeches
16% - Tadpoles
also - Earthworms, Crabs, Anurans

Reproduction: There is very little evidence on this subject. The species is considered
viviparous.

Behavior: Terrestrial species displaying both diurnal and nocturnal activity, although it is believed to forage exclusively at night. As other species of the same genus, T. melanogaster prefers habitats with scattered rocks, fallen tree trunks, fallen leaves and other objects that can serve as shelters.

Habitat: Inhabits principally pine - oak forests and xeric shrubs, always in a vicinity of a water body.

text: Chris Grünwald