[2] The subspecies previously known as C. d. collilineatus and C. d. cascavella were moved to the synonymy of C. d. terrificus following the publication of a paper by Wüster et al. in 2005.

The color of the belly varies, it can be white or yellowish, with light gray spots, becoming darker towards the tail.

The species is more active at dusk and in the early hours of the morning; it is highly alert with little warning signs before striking, but like other rattlesnakes they are seldom aggressive towards humans.

[6] The South American rattlesnake has a seasonal reproductive cycle; competition between males (for access to females) begins around the summer's end, with copulation occurring during the fall, and the birth of the young taking place the following spring/summer.

[6] In Roraima, Brazil it has been reported that the gestation lasts for five months, and they are capable of giving birth to up to 14 young.

[8] The diet consists mainly of rodents, likely due to the great abundance and availability of these animals throughout the year, in most areas where the snakes reside.

It occurs in Colombia and eastern Brazil to southeastern Peru, Bolivia, Paraguay, Uruguay, and northern Argentina (Catamarca, Córdoba, Corrientes, Chaco, Entre Rios, Formosa, La Pampa, La Rioja, Mendoza, Misiones, San Juan, San Luis, Santa Fe, Santiago del Estero and Tucumán).

[2] Bite symptoms are very different from those of Nearctic species[13] due to the presence of neurotoxins (crotoxin and crotamine) that cause progressive paralysis.

Other serious complications may result from systemic disorders (incoagulable blood and general spontaneous bleeding), hypotension, and shock.