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 2 m. Brown with chevron pattern. Known locally in Trinidad as 'Mapepire balsain'. Causes most snakebites in Trinidad and Amazonia.

Hemotoxic venom causes severe local damage and bleeding. About 50 bites per year in Trinidad alone; antivenom available.

Forests, plantations, and farmland of Trinidad, the Amazon basin, Guianas, and northern South America.

Nocturnal. Often found near human settlements. Females give birth to up to 80 live young at once.

Brightly banded red-yellow-black snake up to 1.2 m. Related to cobras and mambas — the only elapid in eastern North America. "Red touch yellow, kill a fellow."

Powerful neurotoxin can cause respiratory paralysis. Bites rare — only ~25 per year in US — but require antivenom (which is increasingly scarce).

Pine flatwoods, scrub oak, leaf litter of Florida, Georgia, Alabama, Mississippi, Louisiana, parts of Texas and northern Mexico.

Secretive and reluctant to bite — must chew to inject venom. Often confused with non-venomous milk snake.

Stocky, aggressive shark up to 3.5 m. Uniquely tolerant of fresh water — found in Mississippi, Amazon, even Lake Nicaragua.

Top contender for most dangerous shark to humans. Hunts in shallow, murky water — exactly where people swim. Many attacks attributed to 'great whites' are actually bull sharks.

Shallow coastal waters, estuaries, rivers — Florida, Gulf of Mexico, Caribbean (Cuba, Bahamas, DR), Lake Nicaragua, Mississippi River, Pacific coasts of Mexico and Central America.

Aggressive and territorial. Tolerates salinity from 0 to 53 ppt. Attacks unprovoked more than other sharks.

Up to 5 m with vertical tiger-like stripes (fade with age). Eats almost anything — license plates, tires, and human remains have been found in their stomachs.

Second only to great white in unprovoked human attacks. Common in Caribbean and Hawaiian waters. Slow but powerful — strikes once and waits.

Tropical and subtropical waters — Florida, Caribbean, Gulf of Mexico, Hawaii.

Solitary, mostly nocturnal. Migrates long distances. Females birth up to 80 live pups.

Dark brown to black scorpion up to 7 cm. The Tityus genus dominates scorpionism in Panama — 28 deaths recorded between 1998–2006. Different toxin profile than Centruroides.

Causes pancreatitis, cardiac arrhythmias, and pulmonary edema. Children especially vulnerable — Panama has one of the highest scorpion sting incidence rates in Central America (52/100,000).

Lowland tropical forests of Panama and northern Colombia. Common in agricultural areas, plantations, rural homes.

Nocturnal. Hides under stones, logs, leaf litter. Often stings agricultural workers and people walking barefoot at night.

Not a jellyfish but a colony. Distinctive blue-purple gas float with 30-metre tentacles trailing below. Drifts onto US Atlantic and Gulf coasts.

Excruciatingly painful sting causing whip-like welts. Rarely lethal, but several deaths recorded from heart failure or drowning after shock.

Atlantic and Gulf coasts — Florida, Texas, Louisiana, North Carolina; sometimes washes up by the thousands.

Drifts on wind via sail-like float. Cannot swim — entirely passive. Tentacles sting for weeks even after death.

Striking red-and-white striped fish with long venomous spines. Originally from Indo-Pacific; invaded the Caribbean and US Atlantic in the 1980s and is now devastating reef ecosystems.

Sting causes severe pain, swelling, sometimes anaphylaxis. Rarely fatal but ER visits common — and lionfish have no predators in their invasive range.

Invasive across Caribbean, Gulf of Mexico, US Atlantic coast from Florida to North Carolina.

Stationary among rocks and reef. Stings only when handled or stepped on. Females release 30,000 eggs every 4 days.

Reddish-brown ant 2–6 mm. Invasive from South America since 1930s; now infests southern US from Texas to Virginia. Aggressive when nest disturbed.

Stings cause burning pustules. Allergic reactions can cause anaphylactic shock — about 80 deaths per year in US attributed to fire ants.

Open sunny areas — lawns, fields, roadsides — across southern US, Caribbean, parts of Mexico.

Builds large mound nests up to 60 cm tall. Step on a mound, hundreds swarm out and sting in unison.