South American Rattlesnake
Crotalus durissus • Order: Squamata, Suborder: Serpentes, Family: Viperidae, Subfamily: Crotalinae, Genus: Crotalus, Species: Crotalus durissus
Widely distributed throughout South America, including Brazil, Venezuela, Peru, Bolivia, Paraguay, Uruguay, and Argentina. It is found in disjunct populations and is notably absent from the Amazon Basin's dense rainforest centers.
Look up South American Rattlesnake in the Snake Encyclopedia →Venomous Status
Highly venomous (Solenoglyphous fangs; long, hollow, retractable fangs at the front of the maxilla).
Danger Level
Extremely Dangerous. It is one of the most medically significant snakes in South America with a high potential for fatalities if antivenom is not administered promptly.
Family
Order: Squamata, Suborder: Serpentes, Family: Viperidae, Subfamily: Crotalinae, Genus: Crotalus, Species: Crotalus durissus
Conservation
IUCN Red List: Least Concern. However, regional populations may be threatened by habitat loss through agriculture and intentional killing by humans.
Physical Description
Robust, thick-bodied snake with a distinct triangular head. Displays prominent keeled scales. Features a 'diamond' or 'cascabel' pattern of rhombs down the back. A signature multi-segmented rattle is present at the tail tip. Coloration is typically shades of brown, grey, and tan.
Size & Dimensions
Specimen appears to be an adult. Typical length ranges from 100 cm to 150 cm (approx. 3.3 to 5 ft), with exceptional specimens reaching up to 180 cm.
Habitat
Prefers dry, open areas such as savannas (Cerrado, Caatinga), grasslands, and scrub forests. It is generally found at elevations from sea level up to roughly 2,500 meters.
Behavior & Temperament
Can be highly defensive when threatened. It utilizes its rattle as a warning signal. While mostly terrestrial and nocturnal or crepuscular, it may bask during the day in cooler weather.
Diet & Feeding
Primarily preys on rodents and other small mammals. It is an ambush predator that uses its heat-sensing pits to locate warm-blooded prey, striking and then tracking the scent of the dying animal.
Reproduction
Ovoviviparous (gives birth to live young). Litter sizes typically range from 6 to 22 neonates depending on the size and health of the mother.
Venom Profile
Combination of neurotoxic (crotoxin), hemotoxic, and myotoxic properties. Unlike many North American rattlesnakes, this species has a strong neurotoxic component causing paralysis and renal failure.
Look-alikes
Could be confused with other Crotalus species or the Bothrops genus (Lanceheads), but is easily distinguished by the presence of a functional rattle and the specific dorsal diamond pattern.
Conservation Status
IUCN Red List: Least Concern. However, regional populations may be threatened by habitat loss through agriculture and intentional killing by humans.
Cultural Significance
Known as 'Cascavel' in Portuguese-speaking regions. It holds significant status in local folklore and is a primary subject of study in South American herpetology and toxicology due to its unique neurotoxic venom.
Notable Features
The presence of 'crotoxin' in its venom is a unique evolutionary trait among rattlesnakes, leading to systemic effects like 'broken neck syndrome' (ptosis and paralysis) in bite victims.