Geographic range: Nearctical, Neotropical: C. triseriatus is native to Mexico. It is found in temperate climates of the Trans Mexican Volcanic Belt from wc. Veracruz through Puebla, Tlaxcala, México, D.F., Morelos and Michoacán. Isolated population in Jalisco and possibly Nayarit.

Subspecies:
Crotalus triseriatus triseriatus - From w. Michoacán to wc. Veracruz.
Crotalus triseriatus armstrongi - highlands of w. Jalisco and possibly nearby Nayarit and Colima.

Physical characteristics: A medium sized venomous snake (50 to 60 cm). Males are bigger than females. Body color can range from olive brown to dark brown and even greenish, but the conspicuous pattern of oval and semioval spots along the back is always present. These dark spots are surrounded by thin lighter line. In the posteroventral region on the head a clearly defined wide, dark (black) line bordered by thin white lines is present.
Dorsal scales ale keeled. Scales of lateral regions are smooth and bigger. Ventral region is pearl gray.

Food habits: Principal food items are lizards, frogs and rodents.

Reproduction: As all the species of the same genus, C. triseriatus is viviparous. Reproductive activity was observed in the fall. Around 10 individuals per clutch were recorded in summer months.

Behavior: A highly diurnal species, with only the occasional juvenile being found active after dark.

Habitat: Inhabits principally coniferous (especially pine -oak) forests of temperate zones, in altitudes over 2000 m. Prefers zacaton (bunch grass) microhabitats with presence of fallen tree trunks and rocks. It was also observed in corn plantations.

Biomes: temperate forest