Up to 1.6 m. Brown with darker triangular blotches. Causes more snakebites than any other species in southeast Brazil. Its venom led to the discovery of ACE inhibitors (blood pressure drugs).

Hemotoxic venom causes severe local damage, hemorrhage, kidney failure. About 20,000 bites per year across Brazil, with 0.1–0.5% mortality even with antivenom.

Atlantic forests and grasslands of southeastern Brazil, Paraguay, northern Argentina, Uruguay.

Nocturnal in summer. Often found near rural homes hunting rodents. Females give birth to up to 20 live young.

Up to 1.8 m. The widest-ranging rattlesnake in South America. Unique among rattlers for highly neurotoxic venom (most have hemotoxic).

Neurotoxin causes paralysis, blindness, kidney failure. Mortality up to 12% without antivenom — much higher than US rattlers. About 1,000 bites/year in Brazil.

Dry savannas, Cerrado, and Caatinga of Brazil, Argentina, Bolivia, Paraguay, Uruguay, Colombia, Venezuela.

Nocturnal in hot weather. Often near villages and farms hunting rodents. Rattles loudly before striking — but doesn't always.

Heavy-bodied pit viper up to 2.5 m. Responsible for more snakebite deaths in Central America than any other species — "the ultimate pit viper".

Highly potent hemotoxin causes catastrophic tissue damage and bleeding. Without antivenom, mortality reaches 7–9%. Aggressive when cornered.

Lowland forests, plantations, banana fields from southern Mexico through Guatemala, Honduras, Nicaragua, Costa Rica, and Panama.

Active hunter at night; sometimes climbs into low vegetation. Females give birth to up to 80 venomous neonates.

Up to 17 cm leg span. Holds Guinness record for most venomous spider. Brown with banded legs; raises front legs in defense.

Neurotoxin causes intense pain, paralysis, suffocation, and (in 1% of cases) death. About 4,000 bites per year in Brazil alone. Hides in banana shipments — found in Europe and US in shops.

Forests of Brazil, Paraguay, northern Argentina, Uruguay, eastern Bolivia. Wanders at night looking for prey — hence the name.

Doesn't build webs. Active at night. Often hides in bananas, shoes, woodpiles, inside houses. Female aggressively defends egg sac.

Glossy black with red hourglass — South American counterpart of the North American black widow. Found across Argentine Pampas, Uruguay, southern Brazil.

Alpha-latrotoxin causes severe muscle cramps, hypertension, sweating. About 1,000 bites per year reported in Argentina alone. Antivenom is widely available and very effective.

Grasslands and pampas of Argentina, Uruguay, southern Brazil, Paraguay. Also found in agricultural areas, woodpiles.

Builds messy tangle webs near the ground. Female bites only when pressed — typically in fields, while harvesting, or while moving objects.

Third-largest cat — up to 100 kg. Spotted rosettes with central dots distinguish it from leopards. In North America found in Mexico and rarely Arizona/New Mexico.

Strongest bite force of any cat — pierces turtle shells and skulls. Attacks on humans rare but occur in Mexican rainforests.

Tropical rainforests of southern Mexico (Chiapas, Yucatán), Belize, Guatemala, Honduras, Nicaragua, Costa Rica, Panama; rare strays into Arizona.

Solitary, mostly nocturnal. Excellent swimmer — hunts caimans, capybaras, deer. Stalks before pouncing.

Heaviest snake on Earth — up to 250 kg and 8 m. Olive-green with black blotches. Lives almost entirely in water in the Amazon basin.

Constricts prey then swallows whole — capable of taking deer, capybaras, even caimans. Documented attacks on humans rare but fatal cases recorded. Drowning + crushing is the killing mechanism.

Slow rivers, swamps, and flooded forests of the Amazon basin — Brazil, Colombia, Venezuela, Peru, Bolivia, Ecuador, Guyana, Suriname, French Guiana.

Mostly aquatic — only eyes and nostrils above water. Ambushes prey at the water's edge. Females eat males after mating.

Small bat (7–9 cm, 25–40 g) that feeds exclusively on blood. Razor-sharp incisors slice skin painlessly; anticoagulant saliva keeps blood flowing.

Top vector of rabies in Latin America — particularly the Amazon. Several outbreaks per year kill dozens. 2005 Brazilian outbreak killed 23. Cattle deaths cost millions.

From Mexico to northern Argentina — caves, hollow trees, abandoned buildings. Most active in Brazil, Peru, Bolivia, Colombia, Ecuador, Venezuela.

Active 30 minutes after sunset. Approaches sleeping victims (humans, cattle) silently. Bite is so light victim doesn't wake — discovered next morning.

Smaller cousin of the black caiman — up to 2.5 m. Named for ridge between eyes resembling spectacles. The most widespread crocodilian in South America.

Less dangerous than black caiman but attacks documented, especially during nesting season. Females aggressively defend nests within 5 m radius.

All freshwater systems from southern Mexico through Colombia, Venezuela, Peru, Ecuador, Bolivia, Brazil, Paraguay, French Guiana, Suriname.

More tolerant of dry seasons than black caiman — buries in mud and aestivates. Active mainly at night.

Up to 33 cm. Red-orange belly, silver flanks, triangular razor-sharp teeth. The 'classic' piranha of Hollywood films.

Reputation as flesh-stripping killers is largely myth. Real attacks on humans occur during dry season when fish are crowded and hungry — bites are nasty but rarely lethal. Hundreds of foot/hand bites yearly.

Amazon, Paraná, and Orinoco river basins — Brazil, Argentina, Paraguay, Uruguay, Bolivia, Peru, Colombia, Venezuela.

Schooling fish. Most aggressive during low water when fish are concentrated. Attracted to blood and thrashing in water.