Neotropical Rattlesnake
Crotalus durissus • Order: Squamata, Suborder: Serpentes, Family: Viperidae, Subfamily: Crotalinae, Genus: Crotalus, Species: Crotalus durissus
Venomous Status
Venomous; Solenoglyphous (possesses large, retractable hollow fangs at the front of the maxilla).
Danger Level
Extremely Dangerous. It has the highest mortality rate among New World rattlesnakes due to its potent neurotoxic venom which can lead to respiratory paralysis and renal failure.
Geographic Range
Widely distributed throughout South America, from Colombia and Venezuela southward to northern Argentina. It is found in disjunct populations across various countries including Brazil, Paraguay, and Uruguay.
Conservation Status
Least Concern (IUCN), though specific subspecies or regional populations may face threats from habitat loss, urbanization, and direct persecution by humans.
Physical Description
Robust body with heavily keeled scales. Features a distinct pair of dark paravertebral stripes on the neck. The dorsal pattern consists of prominent dark, diamond-shaped rhombs with lighter centers. Triangular head, vertical pupils, and a large rattle at the end of the tail.
Size & Dimensions
Specimen appears to be an adult. Typical size ranges from 1.0 to 1.5 meters (3.3 to 4.9 ft), with exceptional individuals reaching up to 1.8 meters (5.9 ft).
Habitat
Primarily inhabits seasonally dry forests, savannas, and scrublands (Caatinga and Cerrado biomes). It generally avoids dense tropical rainforests and is often found at elevations from sea level up to 1,000 meters.
Behavior & Temperament
Generally terrestrial and crepuscular or nocturnal. While it possesses a rattle to warn predators, it can be highly defensive if cornered. Its strike is fast, and it may hold its ground rather than fleeing.
Diet & Feeding
Carnivorous; primarily feeds on rodents (mice, rats) and other small mammals. It is an ambush predator that uses heat-sensing pits to locate prey and venom to immobilize it before consumption.
Reproduction
Ovoviviparous (gives birth to live young). Litter sizes typically range from 10 to 30 neonates. Breeding usually occurs seasonally depending on the specific geographic region.
Venom & Safety
Venom Type
Highly complex; primarily neurotoxic, myotoxic, and coagulant. Unlike many North American rattlesnakes, its venom contains crotoxin, which causes systemic neurocentric effects and muscle breakdown (rhabdomyolysis).
First Aid Advice
Immediate medical emergency. Immobilize the limb, keep the victim calm, and transport to a hospital immediately. Antivenom (specifically polyvalent anticrotalic serum) is the only effective treatment. Do not use tourniquets or ice.
Look-alikes
Could be confused with other South American vipers like Bothrops species (lanceheads), though the presence of the rattle is a definitive diagnostic feature. It lacks the 'X' pattern often seen in Bothrops jararaca.
Conservation Status
Least Concern (IUCN), though specific subspecies or regional populations may face threats from habitat loss, urbanization, and direct persecution by humans.
Cultural Significance
Iconic species in South American folklore and indigenous cultures. It is ecologically vital for controlling rodent populations. It is also the primary source for crotoxin used in medical and biochemical research.
Notable Features
Distinguished from other rattlesnakes by its unique neurotoxic venom profile and the prominent longitudinal stripes on the neck. It is the only rattlesnake species widely distributed as far south as Argentina.