Subspecies of brown bear, recognised by shoulder hump and dished face. Males up to 360 kg. Around 50,000 in Alaska, ~1,800 in lower 48 states.

Charges at 50 km/h; single paw swipe can crush a skull. Around 2–3 fatal attacks per year in North America. Mother with cubs is most dangerous.

Forests, alpine meadows, river valleys of Alaska, western Canada, Montana, Wyoming, Idaho.

Solitary outside breeding. Hibernates Nov–Apr. Excellent swimmer; can outrun a horse on flat ground.

Heavy-bodied pit viper up to 2 m with diamond pattern and black-and-white banded tail. The most widespread rattler in the southwestern US and northern Mexico.

Hemotoxic venom destroys tissue. Causes more snakebite deaths than any other species in the US — about 5–6 per year.

Deserts, scrubland, and rocky outcrops from California to Arkansas, plus most of Mexico.

Ambush predator. Rattles as warning before striking, but startled snakes can bite without warning. Active April–October.

Up to 1.5 m with dark crossbands. The dominant rattlesnake of eastern US deciduous forests. Famous from the Gadsden flag — "Don't Tread on Me".

Potent hemotoxic venom; some populations also have neurotoxic 'canebrake toxin'. About 1 fatal bite per year in the US.

Deciduous forests, rocky hillsides, swamps from New England south to Texas.

Surprisingly docile — usually rattles long before biting. Hibernates communally in rock crevices.

Heavy-bodied water snake up to 1.5 m. Named for the white interior of its mouth, displayed when threatened. The only venomous water snake in North America.

Hemotoxin causes severe tissue damage. Reputation for aggression is exaggerated — but if cornered, will stand ground and strike.

Swamps, slow rivers, lakes of the southeastern US — Louisiana, Florida, Mississippi, Alabama, Georgia.

Equally at home on land and water. Hunts fish, frogs, small mammals. Active day and night in warm weather.

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.

Largest small cat in the world — up to 100 kg, body 2.5 m including tail. Can leap 5 m vertically and 12 m horizontally. Most widespread big cat in the Americas.

Attacks on humans are rare but documented — about 1 fatal attack every 2 years in North America. Targets joggers, cyclists, and children. Strikes from behind.

Mountains, forests, deserts from Canadian Rockies to Patagonia. Wide range of habitats.

Solitary, crepuscular, silent. Doesn't roar — emits eerie screams during mating. Stalks prey for hours.

Up to 4 m and 450 kg. Wider snout than crocodiles. Florida alone hosts 1.3 million; common in golf course ponds and suburban canals.

1–2 fatal attacks per year in the US. Most dangerous near water; will strike from below to grab a leg. Females aggressive defending nests.

Freshwater swamps, rivers, lakes, canals from North Carolina to Texas, plus all of Florida.

Cold-blooded — most active in warm weather. Capable of brief bursts of 17 km/h on land. Average lifespan 35–50 years.

Glossy black female with red hourglass on abdomen. About 13 mm body. Males harmless. The 'classic' black widow of American folklore.

Alpha-latrotoxin causes severe muscle cramps, hypertension, sweating ('latrodectism'). Fatalities now rare with antivenom; ~2,500 bites per year in US.

Woodpiles, sheds, garages, outdoor toilets across southern and eastern US, Mexico.

Builds messy tangle web in corners. Bites only when pressed. Females cannibalize males rarely (myth exaggerated).

Light brown spider, 6–20 mm, with a violin-shaped marking on the head. Six eyes (most spiders have eight). Found in central and southern US.

Cytotoxic venom causes 'loxoscelism' — necrotic skin lesions that can rot for weeks. Severe systemic reactions can cause kidney failure or death.

Closets, attics, woodpiles, shoes, undisturbed areas of homes from Texas to Tennessee, Iowa to Louisiana.

Reclusive (true to its name) — bites only when pressed against skin. Active at night hunting other insects.

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 6 m and 1,900 kg. Pacific population concentrates around northern California (Farallon Islands) and Mexico's Guadalupe Island.

Most fatal unprovoked shark attacks worldwide. About 5–10 fatalities per year globally. Mistakes surfers for seals — the 'investigative bite' is often fatal.

Cool coastal waters of California, Oregon, Washington, Mexico (Pacific), northeastern US, Atlantic Canada.

Apex predator. Migrates thousands of km. Breaches fully out of water when attacking seals.

Tiny tick (3 mm) that transmits Lyme disease. Known by black legs and reddish body. Different from European castor bean tick but similar role.

About 476,000 Lyme disease cases per year in US (CDC estimate). Also transmits anaplasmosis, babesiosis, Powassan virus. Untreated Lyme causes lifelong joint and neurological issues.

Wooded areas, tall grass, deer trails — northeast, upper Midwest, mid-Atlantic US, southern Canada.

Quests on grass tips for passing hosts. Active April–November. Larvae feed on mice (where they pick up Lyme), nymphs and adults on deer and humans.

Up to 90 cm with copper-coloured head and hourglass crossbands. The most common venomous snake in the eastern US — responsible for half of all snakebites.

Hemotoxin is relatively mild — fatalities are extremely rare (less than 1 per decade), but bites are painful and require hospitalization.

Wooded hillsides, rocky outcrops, leaf litter, suburban gardens across eastern US.

Camouflages perfectly with fallen leaves. Often steps on it before noticing. 'Freezes' rather than fleeing.

Smallest of the three North American bears — males 90–250 kg. Despite the name, can be brown, cinnamon, or even white (Kermode). About 800,000 across the continent.

Predatory attacks on humans are rare but documented — about 1 fatal attack per year. Unlike grizzlies, often safe to fight back if attacked.

Forests across Canada, US, and Mexico — from Alaska to Florida to central Mexico.

Excellent climber and swimmer. Bold around campsites and trash; rarely aggressive but conditioned bears are dangerous.

Most abundant deer in North America — about 30 million. Bucks up to 130 kg with branching antlers. White underside of tail flagged when alarmed.

About 200 deaths per year in US — almost all from vehicle collisions. 1.5 million collisions yearly. Bucks attack during November rut; bears and Lyme-tick host.

Forests, fields, suburbs across all of US (except southwest deserts), southern Canada, Mexico.

Crepuscular — peak collisions at dawn and dusk in autumn. Excellent swimmer; jumps 2.5 m high.

Pale yellow-tan, 7–8 cm. The most venomous scorpion in North America. Glows brilliantly under UV light.

Neurotoxic sting causes severe pain, numbness, and in children — convulsions and respiratory failure. Antivenom dramatically reduces mortality.

Rocky deserts and palm oases of Arizona, southern Utah, southeastern California, parts of New Mexico and northern Mexico (Sonora).

Climbs walls, hides under bark and stones. Active at night. Sometimes enters homes. Can survive being frozen overnight.

'Killer bee' — hybrid of African and European honey bees, escaped Brazilian lab in 1957. Spread north and arrived in southern US in 1990; now in Texas, Arizona, Nevada, California, Florida.

Individual sting like normal bee, but they swarm aggressively — attacking in 100s for minor disturbance, pursuing victims 400 m. About 1–2 deaths per year in US.

Southern US (Texas, Arizona, California, Florida), all of Mexico, Guatemala, Honduras, Nicaragua, El Salvador, Costa Rica, Panama, Belize.

Easily provoked by vibration, sound, dark colors, exhalation. Stays angry for 24+ hours after disturbance.

Largest land mammal in North America — bulls up to 1 ton. Once 30 million on the Great Plains; reduced to 500 by 1900, now ~500,000 in herds and ranches.

Causes more injuries in Yellowstone than any other animal — visitors get too close for photos. Charges at 50 km/h despite size.

Yellowstone, Wind Cave, Custer State Park, plus tribal and private herds across US and Canadian plains.

Lives in herds of 20–60. Active dawn and dusk. Tail raised vertically = warning sign.

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.